Merge tag 'for-5.6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs updates from David Sterba:
 "Features, highlights:

   - async discard
       - "mount -o discard=async" to enable it
       - freed extents are not discarded immediatelly, but grouped
         together and trimmed later, with IO rate limiting
       - the "sync" mode submits short extents that could have been
         ignored completely by the device, for SATA prior to 3.1 the
         requests are unqueued and have a big impact on performance
       - the actual discard IO requests have been moved out of
         transaction commit to a worker thread, improving commit latency
       - IO rate and request size can be tuned by sysfs files, for now
         enabled only with CONFIG_BTRFS_DEBUG as we might need to
         add/delete the files and don't have a stable-ish ABI for
         general use, defaults are conservative

   - export device state info in sysfs, eg. missing, writeable

   - no discard of extents known to be untouched on disk (eg. after
     reservation)

   - device stats reset is logged with process name and PID that called
     the ioctl

  Fixes:

   - fix missing hole after hole punching and fsync when using NO_HOLES

   - writeback: range cyclic mode could miss some dirty pages and lead
     to OOM

   - two more corner cases for metadata_uuid change after power loss
     during the change

   - fix infinite loop during fsync after mix of rename operations

  Core changes:

   - qgroup assign returns ENOTCONN when quotas not enabled, used to
     return EINVAL that was confusing

   - device closing does not need to allocate memory anymore

   - snapshot aware code got removed, disabled for years due to
     performance problems, reimplmentation will allow to select wheter
     defrag breaks or does not break COW on shared extents

   - tree-checker:
       - check leaf chunk item size, cross check against number of
         stripes
       - verify location keys for DIR_ITEM, DIR_INDEX and XATTR items

   - new self test for physical -> logical mapping code, used for super
     block range exclusion

   - assertion helpers/macros updated to avoid objtool "unreachable
     code" reports on older compilers or config option combinations"

* tag 'for-5.6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (84 commits)
  btrfs: free block groups after free'ing fs trees
  btrfs: Fix split-brain handling when changing FSID to metadata uuid
  btrfs: Handle another split brain scenario with metadata uuid feature
  btrfs: Factor out metadata_uuid code from find_fsid.
  btrfs: Call find_fsid from find_fsid_inprogress
  Btrfs: fix infinite loop during fsync after rename operations
  btrfs: set trans->drity in btrfs_commit_transaction
  btrfs: drop log root for dropped roots
  btrfs: sysfs, add devid/dev_state kobject and device attributes
  btrfs: Refactor btrfs_rmap_block to improve readability
  btrfs: Add self-tests for btrfs_rmap_block
  btrfs: selftests: Add support for dummy devices
  btrfs: Move and unexport btrfs_rmap_block
  btrfs: separate definition of assertion failure handlers
  btrfs: device stats, log when stats are zeroed
  btrfs: fix improper setting of scanned for range cyclic write cache pages
  btrfs: safely advance counter when looking up bio csums
  btrfs: remove unused member btrfs_device::work
  btrfs: remove unnecessary wrapper get_alloc_profile
  btrfs: add correction to handle -1 edge case in async discard
  ...

40 files changed, 2988 insertions, 1715 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 82200dbca5ac..9a0ff3384381 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -11,7 +11,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
 	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
 	   uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o \
-	   block-rsv.o delalloc-space.o block-group.o
+	   block-rsv.o delalloc-space.o block-group.o discard.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 6934a5b8708f..14851584e245 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -14,6 +14,8 @@
 #include "sysfs.h"
 #include "tree-log.h"
 #include "delalloc-space.h"
+#include "discard.h"
+#include "raid56.h"
 
 /*
  * Return target flags in extended format or 0 if restripe for this chunk_type
@@ -95,7 +97,7 @@ static u64 btrfs_reduce_alloc_profile(struct btrfs_fs_info *fs_info, u64 flags)
 	return extended_to_chunk(flags | allowed);
 }
 
-static u64 get_alloc_profile(struct btrfs_fs_info *fs_info, u64 orig_flags)
+u64 btrfs_get_alloc_profile(struct btrfs_fs_info *fs_info, u64 orig_flags)
 {
 	unsigned seq;
 	u64 flags;
@@ -115,11 +117,6 @@ static u64 get_alloc_profile(struct btrfs_fs_info *fs_info, u64 orig_flags)
 	return btrfs_reduce_alloc_profile(fs_info, flags);
 }
 
-u64 btrfs_get_alloc_profile(struct btrfs_fs_info *fs_info, u64 orig_flags)
-{
-	return get_alloc_profile(fs_info, orig_flags);
-}
-
 void btrfs_get_block_group(struct btrfs_block_group *cache)
 {
 	atomic_inc(&cache->count);
@@ -132,6 +129,15 @@ void btrfs_put_block_group(struct btrfs_block_group *cache)
 		WARN_ON(cache->reserved > 0);
 
 		/*
+		 * A block_group shouldn't be on the discard_list anymore.
+		 * Remove the block_group from the discard_list to prevent us
+		 * from causing a panic due to NULL pointer dereference.
+		 */
+		if (WARN_ON(!list_empty(&cache->discard_list)))
+			btrfs_discard_cancel_work(&cache->fs_info->discard_ctl,
+						  cache);
+
+		/*
 		 * If not empty, someone is still holding mutex of
 		 * full_stripe_lock, which can only be released by caller.
 		 * And it will definitely cause use-after-free when caller
@@ -466,8 +472,8 @@ u64 add_new_free_space(struct btrfs_block_group *block_group, u64 start, u64 end
 		} else if (extent_start > start && extent_start < end) {
 			size = extent_start - start;
 			total_added += size;
-			ret = btrfs_add_free_space(block_group, start,
-						   size);
+			ret = btrfs_add_free_space_async_trimmed(block_group,
+								 start, size);
 			BUG_ON(ret); /* -ENOMEM or logic error */
 			start = extent_end + 1;
 		} else {
@@ -478,7 +484,8 @@ u64 add_new_free_space(struct btrfs_block_group *block_group, u64 start, u64 end
 	if (start < end) {
 		size = end - start;
 		total_added += size;
-		ret = btrfs_add_free_space(block_group, start, size);
+		ret = btrfs_add_free_space_async_trimmed(block_group, start,
+							 size);
 		BUG_ON(ret); /* -ENOMEM or logic error */
 	}
 
@@ -1185,21 +1192,8 @@ static int inc_block_group_ro(struct btrfs_block_group *cache, int force)
 	struct btrfs_space_info *sinfo = cache->space_info;
 	u64 num_bytes;
 	u64 sinfo_used;
-	u64 min_allocable_bytes;
 	int ret = -ENOSPC;
 
-	/*
-	 * We need some metadata space and system metadata space for
-	 * allocating chunks in some corner cases until we force to set
-	 * it to be readonly.
-	 */
-	if ((sinfo->flags &
-	     (BTRFS_BLOCK_GROUP_SYSTEM | BTRFS_BLOCK_GROUP_METADATA)) &&
-	    !force)
-		min_allocable_bytes = SZ_1M;
-	else
-		min_allocable_bytes = 0;
-
 	spin_lock(&sinfo->lock);
 	spin_lock(&cache->lock);
 
@@ -1217,10 +1211,9 @@ static int inc_block_group_ro(struct btrfs_block_group *cache, int force)
 	 * sinfo_used + num_bytes should always <= sinfo->total_bytes.
 	 *
 	 * Here we make sure if we mark this bg RO, we still have enough
-	 * free space as buffer (if min_allocable_bytes is not 0).
+	 * free space as buffer.
 	 */
-	if (sinfo_used + num_bytes + min_allocable_bytes <=
-	    sinfo->total_bytes) {
+	if (sinfo_used + num_bytes <= sinfo->total_bytes) {
 		sinfo->bytes_readonly += num_bytes;
 		cache->ro++;
 		list_add_tail(&cache->ro_list, &sinfo->ro_bgs);
@@ -1233,8 +1226,8 @@ out:
 		btrfs_info(cache->fs_info,
 			"unable to make block group %llu ro", cache->start);
 		btrfs_info(cache->fs_info,
-			"sinfo_used=%llu bg_num_bytes=%llu min_allocable=%llu",
-			sinfo_used, num_bytes, min_allocable_bytes);
+			"sinfo_used=%llu bg_num_bytes=%llu",
+			sinfo_used, num_bytes);
 		btrfs_dump_space_info(cache->fs_info, cache->space_info, 0, 0);
 	}
 	return ret;
@@ -1249,6 +1242,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 	struct btrfs_block_group *block_group;
 	struct btrfs_space_info *space_info;
 	struct btrfs_trans_handle *trans;
+	const bool async_trim_enabled = btrfs_test_opt(fs_info, DISCARD_ASYNC);
 	int ret = 0;
 
 	if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
@@ -1272,10 +1266,28 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		}
 		spin_unlock(&fs_info->unused_bgs_lock);
 
+		btrfs_discard_cancel_work(&fs_info->discard_ctl, block_group);
+
 		mutex_lock(&fs_info->delete_unused_bgs_mutex);
 
 		/* Don't want to race with allocators so take the groups_sem */
 		down_write(&space_info->groups_sem);
+
+		/*
+		 * Async discard moves the final block group discard to be prior
+		 * to the unused_bgs code path.  Therefore, if it's not fully
+		 * trimmed, punt it back to the async discard lists.
+		 */
+		if (btrfs_test_opt(fs_info, DISCARD_ASYNC) &&
+		    !btrfs_is_free_space_trimmed(block_group)) {
+			trace_btrfs_skip_unused_block_group(block_group);
+			up_write(&space_info->groups_sem);
+			/* Requeue if we failed because of async discard */
+			btrfs_discard_queue_work(&fs_info->discard_ctl,
+						 block_group);
+			goto next;
+		}
+
 		spin_lock(&block_group->lock);
 		if (block_group->reserved || block_group->pinned ||
 		    block_group->used || block_group->ro ||
@@ -1347,6 +1359,23 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		}
 		mutex_unlock(&fs_info->unused_bg_unpin_mutex);
 
+		/*
+		 * At this point, the block_group is read only and should fail
+		 * new allocations.  However, btrfs_finish_extent_commit() can
+		 * cause this block_group to be placed back on the discard
+		 * lists because now the block_group isn't fully discarded.
+		 * Bail here and try again later after discarding everything.
+		 */
+		spin_lock(&fs_info->discard_ctl.lock);
+		if (!list_empty(&block_group->discard_list)) {
+			spin_unlock(&fs_info->discard_ctl.lock);
+			btrfs_dec_block_group_ro(block_group);
+			btrfs_discard_queue_work(&fs_info->discard_ctl,
+						 block_group);
+			goto end_trans;
+		}
+		spin_unlock(&fs_info->discard_ctl.lock);
+
 		/* Reset pinned so btrfs_put_block_group doesn't complain */
 		spin_lock(&space_info->lock);
 		spin_lock(&block_group->lock);
@@ -1362,8 +1391,18 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		spin_unlock(&block_group->lock);
 		spin_unlock(&space_info->lock);
 
+		/*
+		 * The normal path here is an unused block group is passed here,
+		 * then trimming is handled in the transaction commit path.
+		 * Async discard interposes before this to do the trimming
+		 * before coming down the unused block group path as trimming
+		 * will no longer be done later in the transaction commit path.
+		 */
+		if (!async_trim_enabled && btrfs_test_opt(fs_info, DISCARD_ASYNC))
+			goto flip_async;
+
 		/* DISCARD can flip during remount */
-		trimming = btrfs_test_opt(fs_info, DISCARD);
+		trimming = btrfs_test_opt(fs_info, DISCARD_SYNC);
 
 		/* Implicit trim during transaction commit. */
 		if (trimming)
@@ -1406,6 +1445,13 @@ next:
 		spin_lock(&fs_info->unused_bgs_lock);
 	}
 	spin_unlock(&fs_info->unused_bgs_lock);
+	return;
+
+flip_async:
+	btrfs_end_transaction(trans);
+	mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+	btrfs_put_block_group(block_group);
+	btrfs_discard_punt_unused_bgs_list(fs_info);
 }
 
 void btrfs_mark_bg_unused(struct btrfs_block_group *bg)
@@ -1516,6 +1562,102 @@ static void set_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
 	write_sequnlock(&fs_info->profiles_lock);
 }
 
+/**
+ * btrfs_rmap_block - Map a physical disk address to a list of logical addresses
+ * @chunk_start:   logical address of block group
+ * @physical:	   physical address to map to logical addresses
+ * @logical:	   return array of logical addresses which map to @physical
+ * @naddrs:	   length of @logical
+ * @stripe_len:    size of IO stripe for the given block group
+ *
+ * Maps a particular @physical disk address to a list of @logical addresses.
+ * Used primarily to exclude those portions of a block group that contain super
+ * block copies.
+ */
+EXPORT_FOR_TESTS
+int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
+		     u64 physical, u64 **logical, int *naddrs, int *stripe_len)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	u64 *buf;
+	u64 bytenr;
+	u64 data_stripe_length;
+	u64 io_stripe_size;
+	int i, nr = 0;
+	int ret = 0;
+
+	em = btrfs_get_chunk_map(fs_info, chunk_start, 1);
+	if (IS_ERR(em))
+		return -EIO;
+
+	map = em->map_lookup;
+	data_stripe_length = em->len;
+	io_stripe_size = map->stripe_len;
+
+	if (map->type & BTRFS_BLOCK_GROUP_RAID10)
+		data_stripe_length = div_u64(data_stripe_length,
+					     map->num_stripes / map->sub_stripes);
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID0)
+		data_stripe_length = div_u64(data_stripe_length, map->num_stripes);
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
+		data_stripe_length = div_u64(data_stripe_length,
+					     nr_data_stripes(map));
+		io_stripe_size = map->stripe_len * nr_data_stripes(map);
+	}
+
+	buf = kcalloc(map->num_stripes, sizeof(u64), GFP_NOFS);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	for (i = 0; i < map->num_stripes; i++) {
+		bool already_inserted = false;
+		u64 stripe_nr;
+		int j;
+
+		if (!in_range(physical, map->stripes[i].physical,
+			      data_stripe_length))
+			continue;
+
+		stripe_nr = physical - map->stripes[i].physical;
+		stripe_nr = div64_u64(stripe_nr, map->stripe_len);
+
+		if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
+			stripe_nr = stripe_nr * map->num_stripes + i;
+			stripe_nr = div_u64(stripe_nr, map->sub_stripes);
+		} else if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
+			stripe_nr = stripe_nr * map->num_stripes + i;
+		}
+		/*
+		 * The remaining case would be for RAID56, multiply by
+		 * nr_data_stripes().  Alternatively, just use rmap_len below
+		 * instead of map->stripe_len
+		 */
+
+		bytenr = chunk_start + stripe_nr * io_stripe_size;
+
+		/* Ensure we don't add duplicate addresses */
+		for (j = 0; j < nr; j++) {
+			if (buf[j] == bytenr) {
+				already_inserted = true;
+				break;
+			}
+		}
+
+		if (!already_inserted)
+			buf[nr++] = bytenr;
+	}
+
+	*logical = buf;
+	*naddrs = nr;
+	*stripe_len = io_stripe_size;
+out:
+	free_extent_map(em);
+	return ret;
+}
+
 static int exclude_super_stripes(struct btrfs_block_group *cache)
 {
 	struct btrfs_fs_info *fs_info = cache->fs_info;
@@ -1610,6 +1752,8 @@ static struct btrfs_block_group *btrfs_create_block_group_cache(
 	cache->full_stripe_len = btrfs_full_stripe_len(fs_info, start);
 	set_free_space_tree_thresholds(cache);
 
+	cache->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
+
 	atomic_set(&cache->count, 1);
 	spin_lock_init(&cache->lock);
 	init_rwsem(&cache->data_rwsem);
@@ -1617,6 +1761,7 @@ static struct btrfs_block_group *btrfs_create_block_group_cache(
 	INIT_LIST_HEAD(&cache->cluster_list);
 	INIT_LIST_HEAD(&cache->bg_list);
 	INIT_LIST_HEAD(&cache->ro_list);
+	INIT_LIST_HEAD(&cache->discard_list);
 	INIT_LIST_HEAD(&cache->dirty_list);
 	INIT_LIST_HEAD(&cache->io_list);
 	btrfs_init_free_space_ctl(cache);
@@ -1775,7 +1920,10 @@ static int read_one_block_group(struct btrfs_fs_info *info,
 		inc_block_group_ro(cache, 1);
 	} else if (cache->used == 0) {
 		ASSERT(list_empty(&cache->bg_list));
-		btrfs_mark_bg_unused(cache);
+		if (btrfs_test_opt(info, DISCARD_ASYNC))
+			btrfs_discard_queue_work(&info->discard_ctl, cache);
+		else
+			btrfs_mark_bg_unused(cache);
 	}
 	return 0;
 error:
@@ -2738,8 +2886,10 @@ int btrfs_update_block_group(struct btrfs_trans_handle *trans,
 		 * dirty list to avoid races between cleaner kthread and space
 		 * cache writeout.
 		 */
-		if (!alloc && old_val == 0)
-			btrfs_mark_bg_unused(cache);
+		if (!alloc && old_val == 0) {
+			if (!btrfs_test_opt(info, DISCARD_ASYNC))
+				btrfs_mark_bg_unused(cache);
+		}
 
 		btrfs_put_block_group(cache);
 		total -= num_bytes;
diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index 9b409676c4b2..107bb557ca8d 100644
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -13,6 +13,19 @@ enum btrfs_disk_cache_state {
 };
 
 /*
+ * This describes the state of the block_group for async discard.  This is due
+ * to the two pass nature of it where extent discarding is prioritized over
+ * bitmap discarding.  BTRFS_DISCARD_RESET_CURSOR is set when we are resetting
+ * between lists to prevent contention for discard state variables
+ * (eg. discard_cursor).
+ */
+enum btrfs_discard_state {
+	BTRFS_DISCARD_EXTENTS,
+	BTRFS_DISCARD_BITMAPS,
+	BTRFS_DISCARD_RESET_CURSOR,
+};
+
+/*
  * Control flags for do_chunk_alloc's force field CHUNK_ALLOC_NO_FORCE means to
  * only allocate a chunk if we really need one.
  *
@@ -116,7 +129,13 @@ struct btrfs_block_group {
 	/* For read-only block groups */
 	struct list_head ro_list;
 
+	/* For discard operations */
 	atomic_t trimming;
+	struct list_head discard_list;
+	int discard_index;
+	u64 discard_eligible_time;
+	u64 discard_cursor;
+	enum btrfs_discard_state discard_state;
 
 	/* For dirty block groups */
 	struct list_head dirty_list;
@@ -158,6 +177,22 @@ struct btrfs_block_group {
 	struct btrfs_full_stripe_locks_tree full_stripe_locks_root;
 };
 
+static inline u64 btrfs_block_group_end(struct btrfs_block_group *block_group)
+{
+	return (block_group->start + block_group->length);
+}
+
+static inline bool btrfs_is_block_group_data_only(
+					struct btrfs_block_group *block_group)
+{
+	/*
+	 * In mixed mode the fragmentation is expected to be high, lowering the
+	 * efficiency, so only proper data block groups are considered.
+	 */
+	return (block_group->flags & BTRFS_BLOCK_GROUP_DATA) &&
+	       !(block_group->flags & BTRFS_BLOCK_GROUP_METADATA);
+}
+
 #ifdef CONFIG_BTRFS_DEBUG
 static inline int btrfs_should_fragment_free_space(
 		struct btrfs_block_group *block_group)
@@ -248,4 +283,9 @@ static inline int btrfs_block_group_done(struct btrfs_block_group *cache)
 		cache->cached == BTRFS_CACHE_ERROR;
 }
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
+		     u64 physical, u64 **logical, int *naddrs, int *stripe_len);
+#endif
+
 #endif /* BTRFS_BLOCK_GROUP_H */
diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index 0b52ab4cb964..a0ce69f2d27c 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -629,7 +629,6 @@ static struct btrfsic_dev_state *btrfsic_dev_state_hashtable_lookup(dev_t dev,
 static int btrfsic_process_superblock(struct btrfsic_state *state,
 				      struct btrfs_fs_devices *fs_devices)
 {
-	struct btrfs_fs_info *fs_info = state->fs_info;
 	struct btrfs_super_block *selected_super;
 	struct list_head *dev_head = &fs_devices->devices;
 	struct btrfs_device *device;
@@ -637,7 +636,6 @@ static int btrfsic_process_superblock(struct btrfsic_state *state,
 	int ret = 0;
 	int pass;
 
-	BUG_ON(NULL == state);
 	selected_super = kzalloc(sizeof(*selected_super), GFP_NOFS);
 	if (NULL == selected_super) {
 		pr_info("btrfsic: error, kmalloc failed!\n");
@@ -700,7 +698,7 @@ static int btrfsic_process_superblock(struct btrfsic_state *state,
 			break;
 		}
 
-		num_copies = btrfs_num_copies(fs_info, next_bytenr,
+		num_copies = btrfs_num_copies(state->fs_info, next_bytenr,
 					      state->metablock_size);
 		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
 			pr_info("num_copies(log_bytenr=%llu) = %d\n",
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 43e1660f450f..de95ad27722f 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -763,7 +763,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 
 			if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
 				ret = btrfs_lookup_bio_sums(inode, comp_bio,
-							    sums);
+							    (u64)-1, sums);
 				BUG_ON(ret); /* -ENOMEM */
 			}
 
@@ -791,7 +791,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	BUG_ON(ret); /* -ENOMEM */
 
 	if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
-		ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
+		ret = btrfs_lookup_bio_sums(inode, comp_bio, (u64)-1, sums);
 		BUG_ON(ret); /* -ENOMEM */
 	}
 
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 54efb21c2727..f90b82050d2d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -101,6 +101,14 @@ struct btrfs_ref;
 
 #define BTRFS_MAX_EXTENT_SIZE SZ_128M
 
+/*
+ * Deltas are an effective way to populate global statistics.  Give macro names
+ * to make it clear what we're doing.  An example is discard_extents in
+ * btrfs_free_space_ctl.
+ */
+#define BTRFS_STAT_NR_ENTRIES	2
+#define BTRFS_STAT_CURR		0
+#define BTRFS_STAT_PREV		1
 
 /*
  * Count how many BTRFS_MAX_EXTENT_SIZE cover the @size
@@ -440,6 +448,36 @@ struct btrfs_full_stripe_locks_tree {
 	struct mutex lock;
 };
 
+/* Discard control. */
+/*
+ * Async discard uses multiple lists to differentiate the discard filter
+ * parameters.  Index 0 is for completely free block groups where we need to
+ * ensure the entire block group is trimmed without being lossy.  Indices
+ * afterwards represent monotonically decreasing discard filter sizes to
+ * prioritize what should be discarded next.
+ */
+#define BTRFS_NR_DISCARD_LISTS		3
+#define BTRFS_DISCARD_INDEX_UNUSED	0
+#define BTRFS_DISCARD_INDEX_START	1
+
+struct btrfs_discard_ctl {
+	struct workqueue_struct *discard_workers;
+	struct delayed_work work;
+	spinlock_t lock;
+	struct btrfs_block_group *block_group;
+	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
+	u64 prev_discard;
+	atomic_t discardable_extents;
+	atomic64_t discardable_bytes;
+	u64 max_discard_size;
+	unsigned long delay;
+	u32 iops_limit;
+	u32 kbps_limit;
+	u64 discard_extent_bytes;
+	u64 discard_bitmap_bytes;
+	atomic64_t discard_bytes_saved;
+};
+
 /* delayed seq elem */
 struct seq_list {
 	struct list_head list;
@@ -526,6 +564,9 @@ enum {
 	 * so we don't need to offload checksums to workqueues.
 	 */
 	BTRFS_FS_CSUM_IMPL_FAST,
+
+	/* Indicate that the discard workqueue can service discards. */
+	BTRFS_FS_DISCARD_RUNNING,
 };
 
 struct btrfs_fs_info {
@@ -816,6 +857,8 @@ struct btrfs_fs_info {
 	struct btrfs_workqueue *scrub_wr_completion_workers;
 	struct btrfs_workqueue *scrub_parity_workers;
 
+	struct btrfs_discard_ctl discard_ctl;
+
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	u32 check_integrity_print_mask;
 #endif
@@ -902,6 +945,11 @@ struct btrfs_fs_info {
 	spinlock_t ref_verify_lock;
 	struct rb_root block_tree;
 #endif
+
+#ifdef CONFIG_BTRFS_DEBUG
+	struct kobject *debug_kobj;
+	struct kobject *discard_debug_kobj;
+#endif
 };
 
 static inline struct btrfs_fs_info *btrfs_sb(struct super_block *sb)
@@ -1170,7 +1218,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
 #define BTRFS_MOUNT_FLUSHONCOMMIT       (1 << 7)
 #define BTRFS_MOUNT_SSD_SPREAD		(1 << 8)
 #define BTRFS_MOUNT_NOSSD		(1 << 9)
-#define BTRFS_MOUNT_DISCARD		(1 << 10)
+#define BTRFS_MOUNT_DISCARD_SYNC	(1 << 10)
 #define BTRFS_MOUNT_FORCE_COMPRESS      (1 << 11)
 #define BTRFS_MOUNT_SPACE_CACHE		(1 << 12)
 #define BTRFS_MOUNT_CLEAR_CACHE		(1 << 13)
@@ -1189,6 +1237,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
 #define BTRFS_MOUNT_FREE_SPACE_TREE	(1 << 26)
 #define BTRFS_MOUNT_NOLOGREPLAY		(1 << 27)
 #define BTRFS_MOUNT_REF_VERIFY		(1 << 28)
+#define BTRFS_MOUNT_DISCARD_ASYNC	(1 << 29)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(2048)
@@ -2449,8 +2498,8 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_ref *ref);
 
 int btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
 			       u64 start, u64 len, int delalloc);
-int btrfs_free_and_pin_reserved_extent(struct btrfs_fs_info *fs_info,
-				       u64 start, u64 len);
+int btrfs_pin_reserved_extent(struct btrfs_fs_info *fs_info, u64 start,
+			      u64 len);
 void btrfs_prepare_extent_commit(struct btrfs_fs_info *fs_info);
 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans);
 int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
@@ -2789,9 +2838,7 @@ struct btrfs_dio_private;
 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 		    struct btrfs_root *root, u64 bytenr, u64 len);
 blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
-				   u8 *dst);
-blk_status_t btrfs_lookup_bio_sums_dio(struct inode *inode, struct bio *bio,
-			      u64 logical_offset);
+				   u64 offset, u8 *dst);
 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     u64 objectid, u64 pos,
@@ -2877,7 +2924,7 @@ struct inode *btrfs_iget(struct super_block *s, struct btrfs_key *location,
 			 struct btrfs_root *root);
 struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 				    struct page *page, size_t pg_offset,
-				    u64 start, u64 end, int create);
+				    u64 start, u64 end);
 int btrfs_update_inode(struct btrfs_trans_handle *trans,
 			      struct btrfs_root *root,
 			      struct inode *inode);
@@ -3110,17 +3157,21 @@ do {								\
 	rcu_read_unlock();					\
 } while (0)
 
-__cold
-static inline void assfail(const char *expr, const char *file, int line)
+#ifdef CONFIG_BTRFS_ASSERT
+__cold __noreturn
+static inline void assertfail(const char *expr, const char *file, int line)
 {
-	if (IS_ENABLED(CONFIG_BTRFS_ASSERT)) {
-		pr_err("assertion failed: %s, in %s:%d\n", expr, file, line);
-		BUG();
-	}
+	pr_err("assertion failed: %s, in %s:%d\n", expr, file, line);
+	BUG();
 }
 
-#define ASSERT(expr)	\
-	(likely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
+#define ASSERT(expr)						\
+	(likely(expr) ? (void)0 : assertfail(#expr, __FILE__, __LINE__))
+
+#else
+static inline void assertfail(const char *expr, const char* file, int line) { }
+#define ASSERT(expr)	(void)(expr)
+#endif
 
 /*
  * Use that for functions that are conditionally exported for sanity tests but
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index ba4d8f375b3c..2ca2a09d0e23 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -704,6 +704,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 
 	/* replace the sysfs entry */
 	btrfs_sysfs_rm_device_link(fs_info->fs_devices, src_device);
+	btrfs_sysfs_update_devid(tgt_device);
 	btrfs_rm_dev_replace_free_srcdev(src_device);
 
 	/* write back the superblocks */
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
new file mode 100644
index 000000000000..5615320fa659
--- /dev/null
+++ b/fs/btrfs/discard.c
@@ -0,0 +1,702 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/ktime.h>
+#include <linux/list.h>
+#include <linux/math64.h>
+#include <linux/sizes.h>
+#include <linux/workqueue.h>
+#include "ctree.h"
+#include "block-group.h"
+#include "discard.h"
+#include "free-space-cache.h"
+
+/*
+ * This contains the logic to handle async discard.
+ *
+ * Async discard manages trimming of free space outside of transaction commit.
+ * Discarding is done by managing the block_groups on a LRU list based on free
+ * space recency.  Two passes are used to first prioritize discarding extents
+ * and then allow for trimming in the bitmap the best opportunity to coalesce.
+ * The block_groups are maintained on multiple lists to allow for multiple
+ * passes with different discard filter requirements.  A delayed work item is
+ * used to manage discarding with timeout determined by a max of the delay
+ * incurred by the iops rate limit, the byte rate limit, and the max delay of
+ * BTRFS_DISCARD_MAX_DELAY.
+ *
+ * Note, this only keeps track of block_groups that are explicitly for data.
+ * Mixed block_groups are not supported.
+ *
+ * The first list is special to manage discarding of fully free block groups.
+ * This is necessary because we issue a final trim for a full free block group
+ * after forgetting it.  When a block group becomes unused, instead of directly
+ * being added to the unused_bgs list, we add it to this first list.  Then
+ * from there, if it becomes fully discarded, we place it onto the unused_bgs
+ * list.
+ *
+ * The in-memory free space cache serves as the backing state for discard.
+ * Consequently this means there is no persistence.  We opt to load all the
+ * block groups in as not discarded, so the mount case degenerates to the
+ * crashing case.
+ *
+ * As the free space cache uses bitmaps, there exists a tradeoff between
+ * ease/efficiency for find_free_extent() and the accuracy of discard state.
+ * Here we opt to let untrimmed regions merge with everything while only letting
+ * trimmed regions merge with other trimmed regions.  This can cause
+ * overtrimming, but the coalescing benefit seems to be worth it.  Additionally,
+ * bitmap state is tracked as a whole.  If we're able to fully trim a bitmap,
+ * the trimmed flag is set on the bitmap.  Otherwise, if an allocation comes in,
+ * this resets the state and we will retry trimming the whole bitmap.  This is a
+ * tradeoff between discard state accuracy and the cost of accounting.
+ */
+
+/* This is an initial delay to give some chance for block reuse */
+#define BTRFS_DISCARD_DELAY		(120ULL * NSEC_PER_SEC)
+#define BTRFS_DISCARD_UNUSED_DELAY	(10ULL * NSEC_PER_SEC)
+
+/* Target completion latency of discarding all discardable extents */
+#define BTRFS_DISCARD_TARGET_MSEC	(6 * 60 * 60UL * MSEC_PER_SEC)
+#define BTRFS_DISCARD_MIN_DELAY_MSEC	(1UL)
+#define BTRFS_DISCARD_MAX_DELAY_MSEC	(1000UL)
+#define BTRFS_DISCARD_MAX_IOPS		(10U)
+
+/* Montonically decreasing minimum length filters after index 0 */
+static int discard_minlen[BTRFS_NR_DISCARD_LISTS] = {
+	0,
+	BTRFS_ASYNC_DISCARD_MAX_FILTER,
+	BTRFS_ASYNC_DISCARD_MIN_FILTER
+};
+
+static struct list_head *get_discard_list(struct btrfs_discard_ctl *discard_ctl,
+					  struct btrfs_block_group *block_group)
+{
+	return &discard_ctl->discard_list[block_group->discard_index];
+}
+
+static void __add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
+				  struct btrfs_block_group *block_group)
+{
+	if (!btrfs_run_discard_work(discard_ctl))
+		return;
+
+	if (list_empty(&block_group->discard_list) ||
+	    block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED) {
+		if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED)
+			block_group->discard_index = BTRFS_DISCARD_INDEX_START;
+		block_group->discard_eligible_time = (ktime_get_ns() +
+						      BTRFS_DISCARD_DELAY);
+		block_group->discard_state = BTRFS_DISCARD_RESET_CURSOR;
+	}
+
+	list_move_tail(&block_group->discard_list,
+		       get_discard_list(discard_ctl, block_group));
+}
+
+static void add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
+				struct btrfs_block_group *block_group)
+{
+	if (!btrfs_is_block_group_data_only(block_group))
+		return;
+
+	spin_lock(&discard_ctl->lock);
+	__add_to_discard_list(discard_ctl, block_group);
+	spin_unlock(&discard_ctl->lock);
+}
+
+static void add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
+				       struct btrfs_block_group *block_group)
+{
+	spin_lock(&discard_ctl->lock);
+
+	if (!btrfs_run_discard_work(discard_ctl)) {
+		spin_unlock(&discard_ctl->lock);
+		return;
+	}
+
+	list_del_init(&block_group->discard_list);
+
+	block_group->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
+	block_group->discard_eligible_time = (ktime_get_ns() +
+					      BTRFS_DISCARD_UNUSED_DELAY);
+	block_group->discard_state = BTRFS_DISCARD_RESET_CURSOR;
+	list_add_tail(&block_group->discard_list,
+		      &discard_ctl->discard_list[BTRFS_DISCARD_INDEX_UNUSED]);
+
+	spin_unlock(&discard_ctl->lock);
+}
+
+static bool remove_from_discard_list(struct btrfs_discard_ctl *discard_ctl,
+				     struct btrfs_block_group *block_group)
+{
+	bool running = false;
+
+	spin_lock(&discard_ctl->lock);
+
+	if (block_group == discard_ctl->block_group) {
+		running = true;
+		discard_ctl->block_group = NULL;
+	}
+
+	block_group->discard_eligible_time = 0;
+	list_del_init(&block_group->discard_list);
+
+	spin_unlock(&discard_ctl->lock);
+
+	return running;
+}
+
+/**
+ * find_next_block_group - find block_group that's up next for discarding
+ * @discard_ctl: discard control
+ * @now: current time
+ *
+ * Iterate over the discard lists to find the next block_group up for
+ * discarding checking the discard_eligible_time of block_group.
+ */
+static struct btrfs_block_group *find_next_block_group(
+					struct btrfs_discard_ctl *discard_ctl,
+					u64 now)
+{
+	struct btrfs_block_group *ret_block_group = NULL, *block_group;
+	int i;
+
+	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++) {
+		struct list_head *discard_list = &discard_ctl->discard_list[i];
+
+		if (!list_empty(discard_list)) {
+			block_group = list_first_entry(discard_list,
+						       struct btrfs_block_group,
+						       discard_list);
+
+			if (!ret_block_group)
+				ret_block_group = block_group;
+
+			if (ret_block_group->discard_eligible_time < now)
+				break;
+
+			if (ret_block_group->discard_eligible_time >
+			    block_group->discard_eligible_time)
+				ret_block_group = block_group;
+		}
+	}
+
+	return ret_block_group;
+}
+
+/**
+ * peek_discard_list - wrap find_next_block_group()
+ * @discard_ctl: discard control
+ * @discard_state: the discard_state of the block_group after state management
+ * @discard_index: the discard_index of the block_group after state management
+ *
+ * This wraps find_next_block_group() and sets the block_group to be in use.
+ * discard_state's control flow is managed here.  Variables related to
+ * discard_state are reset here as needed (eg discard_cursor).  @discard_state
+ * and @discard_index are remembered as it may change while we're discarding,
+ * but we want the discard to execute in the context determined here.
+ */
+static struct btrfs_block_group *peek_discard_list(
+					struct btrfs_discard_ctl *discard_ctl,
+					enum btrfs_discard_state *discard_state,
+					int *discard_index)
+{
+	struct btrfs_block_group *block_group;
+	const u64 now = ktime_get_ns();
+
+	spin_lock(&discard_ctl->lock);
+again:
+	block_group = find_next_block_group(discard_ctl, now);
+
+	if (block_group && now > block_group->discard_eligible_time) {
+		if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED &&
+		    block_group->used != 0) {
+			if (btrfs_is_block_group_data_only(block_group))
+				__add_to_discard_list(discard_ctl, block_group);
+			else
+				list_del_init(&block_group->discard_list);
+			goto again;
+		}
+		if (block_group->discard_state == BTRFS_DISCARD_RESET_CURSOR) {
+			block_group->discard_cursor = block_group->start;
+			block_group->discard_state = BTRFS_DISCARD_EXTENTS;
+		}
+		discard_ctl->block_group = block_group;
+		*discard_state = block_group->discard_state;
+		*discard_index = block_group->discard_index;
+	} else {
+		block_group = NULL;
+	}
+
+	spin_unlock(&discard_ctl->lock);
+
+	return block_group;
+}
+
+/**
+ * btrfs_discard_check_filter - updates a block groups filters
+ * @block_group: block group of interest
+ * @bytes: recently freed region size after coalescing
+ *
+ * Async discard maintains multiple lists with progressively smaller filters
+ * to prioritize discarding based on size.  Should a free space that matches
+ * a larger filter be returned to the free_space_cache, prioritize that discard
+ * by moving @block_group to the proper filter.
+ */
+void btrfs_discard_check_filter(struct btrfs_block_group *block_group,
+				u64 bytes)
+{
+	struct btrfs_discard_ctl *discard_ctl;
+
+	if (!block_group ||
+	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+		return;
+
+	discard_ctl = &block_group->fs_info->discard_ctl;
+
+	if (block_group->discard_index > BTRFS_DISCARD_INDEX_START &&
+	    bytes >= discard_minlen[block_group->discard_index - 1]) {
+		int i;
+
+		remove_from_discard_list(discard_ctl, block_group);
+
+		for (i = BTRFS_DISCARD_INDEX_START; i < BTRFS_NR_DISCARD_LISTS;
+		     i++) {
+			if (bytes >= discard_minlen[i]) {
+				block_group->discard_index = i;
+				add_to_discard_list(discard_ctl, block_group);
+				break;
+			}
+		}
+	}
+}
+
+/**
+ * btrfs_update_discard_index - moves a block group along the discard lists
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * Increment @block_group's discard_index.  If it falls of the list, let it be.
+ * Otherwise add it back to the appropriate list.
+ */
+static void btrfs_update_discard_index(struct btrfs_discard_ctl *discard_ctl,
+				       struct btrfs_block_group *block_group)
+{
+	block_group->discard_index++;
+	if (block_group->discard_index == BTRFS_NR_DISCARD_LISTS) {
+		block_group->discard_index = 1;
+		return;
+	}
+
+	add_to_discard_list(discard_ctl, block_group);
+}
+
+/**
+ * btrfs_discard_cancel_work - remove a block_group from the discard lists
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * This removes @block_group from the discard lists.  If necessary, it waits on
+ * the current work and then reschedules the delayed work.
+ */
+void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
+			       struct btrfs_block_group *block_group)
+{
+	if (remove_from_discard_list(discard_ctl, block_group)) {
+		cancel_delayed_work_sync(&discard_ctl->work);
+		btrfs_discard_schedule_work(discard_ctl, true);
+	}
+}
+
+/**
+ * btrfs_discard_queue_work - handles queuing the block_groups
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * This maintains the LRU order of the discard lists.
+ */
+void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
+			      struct btrfs_block_group *block_group)
+{
+	if (!block_group || !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+		return;
+
+	if (block_group->used == 0)
+		add_to_discard_unused_list(discard_ctl, block_group);
+	else
+		add_to_discard_list(discard_ctl, block_group);
+
+	if (!delayed_work_pending(&discard_ctl->work))
+		btrfs_discard_schedule_work(discard_ctl, false);
+}
+
+/**
+ * btrfs_discard_schedule_work - responsible for scheduling the discard work
+ * @discard_ctl: discard control
+ * @override: override the current timer
+ *
+ * Discards are issued by a delayed workqueue item.  @override is used to
+ * update the current delay as the baseline delay interval is reevaluated on
+ * transaction commit.  This is also maxed with any other rate limit.
+ */
+void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
+				 bool override)
+{
+	struct btrfs_block_group *block_group;
+	const u64 now = ktime_get_ns();
+
+	spin_lock(&discard_ctl->lock);
+
+	if (!btrfs_run_discard_work(discard_ctl))
+		goto out;
+
+	if (!override && delayed_work_pending(&discard_ctl->work))
+		goto out;
+
+	block_group = find_next_block_group(discard_ctl, now);
+	if (block_group) {
+		unsigned long delay = discard_ctl->delay;
+		u32 kbps_limit = READ_ONCE(discard_ctl->kbps_limit);
+
+		/*
+		 * A single delayed workqueue item is responsible for
+		 * discarding, so we can manage the bytes rate limit by keeping
+		 * track of the previous discard.
+		 */
+		if (kbps_limit && discard_ctl->prev_discard) {
+			u64 bps_limit = ((u64)kbps_limit) * SZ_1K;
+			u64 bps_delay = div64_u64(discard_ctl->prev_discard *
+						  MSEC_PER_SEC, bps_limit);
+
+			delay = max(delay, msecs_to_jiffies(bps_delay));
+		}
+
+		/*
+		 * This timeout is to hopefully prevent immediate discarding
+		 * in a recently allocated block group.
+		 */
+		if (now < block_group->discard_eligible_time) {
+			u64 bg_timeout = block_group->discard_eligible_time - now;
+
+			delay = max(delay, nsecs_to_jiffies(bg_timeout));
+		}
+
+		mod_delayed_work(discard_ctl->discard_workers,
+				 &discard_ctl->work, delay);
+	}
+out:
+	spin_unlock(&discard_ctl->lock);
+}
+
+/**
+ * btrfs_finish_discard_pass - determine next step of a block_group
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * This determines the next step for a block group after it's finished going
+ * through a pass on a discard list.  If it is unused and fully trimmed, we can
+ * mark it unused and send it to the unused_bgs path.  Otherwise, pass it onto
+ * the appropriate filter list or let it fall off.
+ */
+static void btrfs_finish_discard_pass(struct btrfs_discard_ctl *discard_ctl,
+				      struct btrfs_block_group *block_group)
+{
+	remove_from_discard_list(discard_ctl, block_group);
+
+	if (block_group->used == 0) {
+		if (btrfs_is_free_space_trimmed(block_group))
+			btrfs_mark_bg_unused(block_group);
+		else
+			add_to_discard_unused_list(discard_ctl, block_group);
+	} else {
+		btrfs_update_discard_index(discard_ctl, block_group);
+	}
+}
+
+/**
+ * btrfs_discard_workfn - discard work function
+ * @work: work
+ *
+ * This finds the next block_group to start discarding and then discards a
+ * single region.  It does this in a two-pass fashion: first extents and second
+ * bitmaps.  Completely discarded block groups are sent to the unused_bgs path.
+ */
+static void btrfs_discard_workfn(struct work_struct *work)
+{
+	struct btrfs_discard_ctl *discard_ctl;
+	struct btrfs_block_group *block_group;
+	enum btrfs_discard_state discard_state;
+	int discard_index = 0;
+	u64 trimmed = 0;
+	u64 minlen = 0;
+
+	discard_ctl = container_of(work, struct btrfs_discard_ctl, work.work);
+
+	block_group = peek_discard_list(discard_ctl, &discard_state,
+					&discard_index);
+	if (!block_group || !btrfs_run_discard_work(discard_ctl))
+		return;
+
+	/* Perform discarding */
+	minlen = discard_minlen[discard_index];
+
+	if (discard_state == BTRFS_DISCARD_BITMAPS) {
+		u64 maxlen = 0;
+
+		/*
+		 * Use the previous levels minimum discard length as the max
+		 * length filter.  In the case something is added to make a
+		 * region go beyond the max filter, the entire bitmap is set
+		 * back to BTRFS_TRIM_STATE_UNTRIMMED.
+		 */
+		if (discard_index != BTRFS_DISCARD_INDEX_UNUSED)
+			maxlen = discard_minlen[discard_index - 1];
+
+		btrfs_trim_block_group_bitmaps(block_group, &trimmed,
+				       block_group->discard_cursor,
+				       btrfs_block_group_end(block_group),
+				       minlen, maxlen, true);
+		discard_ctl->discard_bitmap_bytes += trimmed;
+	} else {
+		btrfs_trim_block_group_extents(block_group, &trimmed,
+				       block_group->discard_cursor,
+				       btrfs_block_group_end(block_group),
+				       minlen, true);
+		discard_ctl->discard_extent_bytes += trimmed;
+	}
+
+	discard_ctl->prev_discard = trimmed;
+
+	/* Determine next steps for a block_group */
+	if (block_group->discard_cursor >= btrfs_block_group_end(block_group)) {
+		if (discard_state == BTRFS_DISCARD_BITMAPS) {
+			btrfs_finish_discard_pass(discard_ctl, block_group);
+		} else {
+			block_group->discard_cursor = block_group->start;
+			spin_lock(&discard_ctl->lock);
+			if (block_group->discard_state !=
+			    BTRFS_DISCARD_RESET_CURSOR)
+				block_group->discard_state =
+							BTRFS_DISCARD_BITMAPS;
+			spin_unlock(&discard_ctl->lock);
+		}
+	}
+
+	spin_lock(&discard_ctl->lock);
+	discard_ctl->block_group = NULL;
+	spin_unlock(&discard_ctl->lock);
+
+	btrfs_discard_schedule_work(discard_ctl, false);
+}
+
+/**
+ * btrfs_run_discard_work - determines if async discard should be running
+ * @discard_ctl: discard control
+ *
+ * Checks if the file system is writeable and BTRFS_FS_DISCARD_RUNNING is set.
+ */
+bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl)
+{
+	struct btrfs_fs_info *fs_info = container_of(discard_ctl,
+						     struct btrfs_fs_info,
+						     discard_ctl);
+
+	return (!(fs_info->sb->s_flags & SB_RDONLY) &&
+		test_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags));
+}
+
+/**
+ * btrfs_discard_calc_delay - recalculate the base delay
+ * @discard_ctl: discard control
+ *
+ * Recalculate the base delay which is based off the total number of
+ * discardable_extents.  Clamp this between the lower_limit (iops_limit or 1ms)
+ * and the upper_limit (BTRFS_DISCARD_MAX_DELAY_MSEC).
+ */
+void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl)
+{
+	s32 discardable_extents;
+	s64 discardable_bytes;
+	u32 iops_limit;
+	unsigned long delay;
+	unsigned long lower_limit = BTRFS_DISCARD_MIN_DELAY_MSEC;
+
+	discardable_extents = atomic_read(&discard_ctl->discardable_extents);
+	if (!discardable_extents)
+		return;
+
+	spin_lock(&discard_ctl->lock);
+
+	/*
+	 * The following is to fix a potential -1 discrepenancy that we're not
+	 * sure how to reproduce. But given that this is the only place that
+	 * utilizes these numbers and this is only called by from
+	 * btrfs_finish_extent_commit() which is synchronized, we can correct
+	 * here.
+	 */
+	if (discardable_extents < 0)
+		atomic_add(-discardable_extents,
+			   &discard_ctl->discardable_extents);
+
+	discardable_bytes = atomic64_read(&discard_ctl->discardable_bytes);
+	if (discardable_bytes < 0)
+		atomic64_add(-discardable_bytes,
+			     &discard_ctl->discardable_bytes);
+
+	if (discardable_extents <= 0) {
+		spin_unlock(&discard_ctl->lock);
+		return;
+	}
+
+	iops_limit = READ_ONCE(discard_ctl->iops_limit);
+	if (iops_limit)
+		lower_limit = max_t(unsigned long, lower_limit,
+				    MSEC_PER_SEC / iops_limit);
+
+	delay = BTRFS_DISCARD_TARGET_MSEC / discardable_extents;
+	delay = clamp(delay, lower_limit, BTRFS_DISCARD_MAX_DELAY_MSEC);
+	discard_ctl->delay = msecs_to_jiffies(delay);
+
+	spin_unlock(&discard_ctl->lock);
+}
+
+/**
+ * btrfs_discard_update_discardable - propagate discard counters
+ * @block_group: block_group of interest
+ * @ctl: free_space_ctl of @block_group
+ *
+ * This propagates deltas of counters up to the discard_ctl.  It maintains a
+ * current counter and a previous counter passing the delta up to the global
+ * stat.  Then the current counter value becomes the previous counter value.
+ */
+void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
+				      struct btrfs_free_space_ctl *ctl)
+{
+	struct btrfs_discard_ctl *discard_ctl;
+	s32 extents_delta;
+	s64 bytes_delta;
+
+	if (!block_group ||
+	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC) ||
+	    !btrfs_is_block_group_data_only(block_group))
+		return;
+
+	discard_ctl = &block_group->fs_info->discard_ctl;
+
+	extents_delta = ctl->discardable_extents[BTRFS_STAT_CURR] -
+			ctl->discardable_extents[BTRFS_STAT_PREV];
+	if (extents_delta) {
+		atomic_add(extents_delta, &discard_ctl->discardable_extents);
+		ctl->discardable_extents[BTRFS_STAT_PREV] =
+			ctl->discardable_extents[BTRFS_STAT_CURR];
+	}
+
+	bytes_delta = ctl->discardable_bytes[BTRFS_STAT_CURR] -
+		      ctl->discardable_bytes[BTRFS_STAT_PREV];
+	if (bytes_delta) {
+		atomic64_add(bytes_delta, &discard_ctl->discardable_bytes);
+		ctl->discardable_bytes[BTRFS_STAT_PREV] =
+			ctl->discardable_bytes[BTRFS_STAT_CURR];
+	}
+}
+
+/**
+ * btrfs_discard_punt_unused_bgs_list - punt unused_bgs list to discard lists
+ * @fs_info: fs_info of interest
+ *
+ * The unused_bgs list needs to be punted to the discard lists because the
+ * order of operations is changed.  In the normal sychronous discard path, the
+ * block groups are trimmed via a single large trim in transaction commit.  This
+ * is ultimately what we are trying to avoid with asynchronous discard.  Thus,
+ * it must be done before going down the unused_bgs path.
+ */
+void btrfs_discard_punt_unused_bgs_list(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_block_group *block_group, *next;
+
+	spin_lock(&fs_info->unused_bgs_lock);
+	/* We enabled async discard, so punt all to the queue */
+	list_for_each_entry_safe(block_group, next, &fs_info->unused_bgs,
+				 bg_list) {
+		list_del_init(&block_group->bg_list);
+		btrfs_discard_queue_work(&fs_info->discard_ctl, block_group);
+	}
+	spin_unlock(&fs_info->unused_bgs_lock);
+}
+
+/**
+ * btrfs_discard_purge_list - purge discard lists
+ * @discard_ctl: discard control
+ *
+ * If we are disabling async discard, we may have intercepted block groups that
+ * are completely free and ready for the unused_bgs path.  As discarding will
+ * now happen in transaction commit or not at all, we can safely mark the
+ * corresponding block groups as unused and they will be sent on their merry
+ * way to the unused_bgs list.
+ */
+static void btrfs_discard_purge_list(struct btrfs_discard_ctl *discard_ctl)
+{
+	struct btrfs_block_group *block_group, *next;
+	int i;
+
+	spin_lock(&discard_ctl->lock);
+	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++) {
+		list_for_each_entry_safe(block_group, next,
+					 &discard_ctl->discard_list[i],
+					 discard_list) {
+			list_del_init(&block_group->discard_list);
+			spin_unlock(&discard_ctl->lock);
+			if (block_group->used == 0)
+				btrfs_mark_bg_unused(block_group);
+			spin_lock(&discard_ctl->lock);
+		}
+	}
+	spin_unlock(&discard_ctl->lock);
+}
+
+void btrfs_discard_resume(struct btrfs_fs_info *fs_info)
+{
+	if (!btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
+		btrfs_discard_cleanup(fs_info);
+		return;
+	}
+
+	btrfs_discard_punt_unused_bgs_list(fs_info);
+
+	set_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags);
+}
+
+void btrfs_discard_stop(struct btrfs_fs_info *fs_info)
+{
+	clear_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags);
+}
+
+void btrfs_discard_init(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	int i;
+
+	spin_lock_init(&discard_ctl->lock);
+	INIT_DELAYED_WORK(&discard_ctl->work, btrfs_discard_workfn);
+
+	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++)
+		INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
+
+	discard_ctl->prev_discard = 0;
+	atomic_set(&discard_ctl->discardable_extents, 0);
+	atomic64_set(&discard_ctl->discardable_bytes, 0);
+	discard_ctl->max_discard_size = BTRFS_ASYNC_DISCARD_DEFAULT_MAX_SIZE;
+	discard_ctl->delay = BTRFS_DISCARD_MAX_DELAY_MSEC;
+	discard_ctl->iops_limit = BTRFS_DISCARD_MAX_IOPS;
+	discard_ctl->kbps_limit = 0;
+	discard_ctl->discard_extent_bytes = 0;
+	discard_ctl->discard_bitmap_bytes = 0;
+	atomic64_set(&discard_ctl->discard_bytes_saved, 0);
+}
+
+void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
+{
+	btrfs_discard_stop(fs_info);
+	cancel_delayed_work_sync(&fs_info->discard_ctl.work);
+	btrfs_discard_purge_list(&fs_info->discard_ctl);
+}
diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
new file mode 100644
index 000000000000..21a15776dac4
--- /dev/null
+++ b/fs/btrfs/discard.h
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef BTRFS_DISCARD_H
+#define BTRFS_DISCARD_H
+
+#include <linux/sizes.h>
+
+struct btrfs_fs_info;
+struct btrfs_discard_ctl;
+struct btrfs_block_group;
+
+/* Discard size limits */
+#define BTRFS_ASYNC_DISCARD_DEFAULT_MAX_SIZE		(SZ_64M)
+#define BTRFS_ASYNC_DISCARD_MAX_FILTER			(SZ_1M)
+#define BTRFS_ASYNC_DISCARD_MIN_FILTER			(SZ_32K)
+
+/* List operations */
+void btrfs_discard_check_filter(struct btrfs_block_group *block_group, u64 bytes);
+
+/* Work operations */
+void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
+			       struct btrfs_block_group *block_group);
+void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
+			      struct btrfs_block_group *block_group);
+void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
+				 bool override);
+bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl);
+
+/* Update operations */
+void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl);
+void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
+				      struct btrfs_free_space_ctl *ctl);
+
+/* Setup/cleanup operations */
+void btrfs_discard_punt_unused_bgs_list(struct btrfs_fs_info *fs_info);
+void btrfs_discard_resume(struct btrfs_fs_info *fs_info);
+void btrfs_discard_stop(struct btrfs_fs_info *fs_info);
+void btrfs_discard_init(struct btrfs_fs_info *fs_info);
+void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info);
+
+#endif
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e0edfdc9c82b..aea48d6ddc0c 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -41,6 +41,7 @@
 #include "tree-checker.h"
 #include "ref-verify.h"
 #include "block-group.h"
+#include "discard.h"
 
 #define BTRFS_SUPER_FLAG_SUPP	(BTRFS_HEADER_FLAG_WRITTEN |\
 				 BTRFS_HEADER_FLAG_RELOC |\
@@ -202,8 +203,8 @@ void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb,
  * that covers the entire device
  */
 struct extent_map *btree_get_extent(struct btrfs_inode *inode,
-		struct page *page, size_t pg_offset, u64 start, u64 len,
-		int create)
+				    struct page *page, size_t pg_offset,
+				    u64 start, u64 len)
 {
 	struct extent_map_tree *em_tree = &inode->extent_tree;
 	struct extent_map *em;
@@ -1953,6 +1954,8 @@ static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
 	btrfs_destroy_workqueue(fs_info->readahead_workers);
 	btrfs_destroy_workqueue(fs_info->flush_workers);
 	btrfs_destroy_workqueue(fs_info->qgroup_rescan_workers);
+	if (fs_info->discard_ctl.discard_workers)
+		destroy_workqueue(fs_info->discard_ctl.discard_workers);
 	/*
 	 * Now that all other work queues are destroyed, we can safely destroy
 	 * the queues used for metadata I/O, since tasks from those other work
@@ -2148,6 +2151,8 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
 				      max_active, 2);
 	fs_info->qgroup_rescan_workers =
 		btrfs_alloc_workqueue(fs_info, "qgroup-rescan", flags, 1, 0);
+	fs_info->discard_ctl.discard_workers =
+		alloc_workqueue("btrfs_discard", WQ_UNBOUND | WQ_FREEZABLE, 1);
 
 	if (!(fs_info->workers && fs_info->delalloc_workers &&
 	      fs_info->flush_workers &&
@@ -2158,7 +2163,8 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
 	      fs_info->endio_freespace_worker && fs_info->rmw_workers &&
 	      fs_info->caching_workers && fs_info->readahead_workers &&
 	      fs_info->fixup_workers && fs_info->delayed_workers &&
-	      fs_info->qgroup_rescan_workers)) {
+	      fs_info->qgroup_rescan_workers &&
+	      fs_info->discard_ctl.discard_workers)) {
 		return -ENOMEM;
 	}
 
@@ -2792,6 +2798,7 @@ int __cold open_ctree(struct super_block *sb,
 
 	btrfs_init_dev_replace_locks(fs_info);
 	btrfs_init_qgroup(fs_info);
+	btrfs_discard_init(fs_info);
 
 	btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
 	btrfs_init_free_cluster(&fs_info->data_alloc_cluster);
@@ -3082,20 +3089,13 @@ int __cold open_ctree(struct super_block *sb,
 
 	btrfs_free_extra_devids(fs_devices, 1);
 
-	ret = btrfs_sysfs_add_fsid(fs_devices, NULL);
+	ret = btrfs_sysfs_add_fsid(fs_devices);
 	if (ret) {
 		btrfs_err(fs_info, "failed to init sysfs fsid interface: %d",
 				ret);
 		goto fail_block_groups;
 	}
 
-	ret = btrfs_sysfs_add_device(fs_devices);
-	if (ret) {
-		btrfs_err(fs_info, "failed to init sysfs device interface: %d",
-				ret);
-		goto fail_fsdev_sysfs;
-	}
-
 	ret = btrfs_sysfs_add_mounted(fs_info);
 	if (ret) {
 		btrfs_err(fs_info, "failed to init sysfs interface: %d", ret);
@@ -3262,6 +3262,7 @@ int __cold open_ctree(struct super_block *sb,
 	}
 
 	btrfs_qgroup_rescan_resume(fs_info);
+	btrfs_discard_resume(fs_info);
 
 	if (!fs_info->uuid_root) {
 		btrfs_info(fs_info, "creating UUID tree");
@@ -3978,6 +3979,9 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
 
 	cancel_work_sync(&fs_info->async_reclaim_work);
 
+	/* Cancel or finish ongoing discard work */
+	btrfs_discard_cleanup(fs_info);
+
 	if (!sb_rdonly(fs_info->sb)) {
 		/*
 		 * The cleaner kthread is stopped, so do one final pass over
@@ -4026,11 +4030,18 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
 	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
 	btrfs_stop_all_workers(fs_info);
 
-	btrfs_free_block_groups(fs_info);
-
 	clear_bit(BTRFS_FS_OPEN, &fs_info->flags);
 	free_root_pointers(fs_info, true);
 
+	/*
+	 * We must free the block groups after dropping the fs_roots as we could
+	 * have had an IO error and have left over tree log blocks that aren't
+	 * cleaned up until the fs roots are freed.  This makes the block group
+	 * accounting appear to be wrong because there's pending reserved bytes,
+	 * so make sure we do the block group cleanup afterwards.
+	 */
+	btrfs_free_block_groups(fs_info);
+
 	iput(fs_info->btree_inode);
 
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 76f123ebb292..8c2d6cf1ce59 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -134,8 +134,8 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
 int btree_lock_page_hook(struct page *page, void *data,
 				void (*flush_fn)(void *));
 struct extent_map *btree_get_extent(struct btrfs_inode *inode,
-		struct page *page, size_t pg_offset, u64 start, u64 len,
-		int create);
+				    struct page *page, size_t pg_offset,
+				    u64 start, u64 len);
 int btrfs_get_num_tolerated_disk_barrier_failures(u64 flags);
 int __init btrfs_end_io_wq_init(void);
 void __cold btrfs_end_io_wq_exit(void);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 274318e9114e..0163fdd59f8f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -32,6 +32,7 @@
 #include "block-rsv.h"
 #include "delalloc-space.h"
 #include "block-group.h"
+#include "discard.h"
 
 #undef SCRAMBLE_DELAYED_REFS
 
@@ -2923,7 +2924,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 			break;
 		}
 
-		if (btrfs_test_opt(fs_info, DISCARD))
+		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
 			ret = btrfs_discard_extent(fs_info, start,
 						   end + 1 - start, NULL);
 
@@ -2934,6 +2935,11 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 		cond_resched();
 	}
 
+	if (btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
+		btrfs_discard_calc_delay(&fs_info->discard_ctl);
+		btrfs_discard_schedule_work(&fs_info->discard_ctl, true);
+	}
+
 	/*
 	 * Transaction is finished.  We don't need the lock anymore.  We
 	 * do need to clean up the block groups in case of a transaction
@@ -3438,7 +3444,6 @@ btrfs_release_block_group(struct btrfs_block_group *cache,
  */
 struct find_free_extent_ctl {
 	/* Basic allocation info */
-	u64 ram_bytes;
 	u64 num_bytes;
 	u64 empty_size;
 	u64 flags;
@@ -3810,7 +3815,6 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
 
 	WARN_ON(num_bytes < fs_info->sectorsize);
 
-	ffe_ctl.ram_bytes = ram_bytes;
 	ffe_ctl.num_bytes = num_bytes;
 	ffe_ctl.empty_size = empty_size;
 	ffe_ctl.flags = flags;
@@ -4165,12 +4169,10 @@ again:
 	return ret;
 }
 
-static int __btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
-					u64 start, u64 len,
-					int pin, int delalloc)
+int btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
+			       u64 start, u64 len, int delalloc)
 {
 	struct btrfs_block_group *cache;
-	int ret = 0;
 
 	cache = btrfs_lookup_block_group(fs_info, start);
 	if (!cache) {
@@ -4179,30 +4181,28 @@ static int __btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
 		return -ENOSPC;
 	}
 
-	if (pin)
-		pin_down_extent(cache, start, len, 1);
-	else {
-		if (btrfs_test_opt(fs_info, DISCARD))
-			ret = btrfs_discard_extent(fs_info, start, len, NULL);
-		btrfs_add_free_space(cache, start, len);
-		btrfs_free_reserved_bytes(cache, len, delalloc);
-		trace_btrfs_reserved_extent_free(fs_info, start, len);
-	}
+	btrfs_add_free_space(cache, start, len);
+	btrfs_free_reserved_bytes(cache, len, delalloc);
+	trace_btrfs_reserved_extent_free(fs_info, start, len);
 
 	btrfs_put_block_group(cache);
-	return ret;
+	return 0;
 }
 
-int btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
-			       u64 start, u64 len, int delalloc)
+int btrfs_pin_reserved_extent(struct btrfs_fs_info *fs_info, u64 start, u64 len)
 {
-	return __btrfs_free_reserved_extent(fs_info, start, len, 0, delalloc);
-}
+	struct btrfs_block_group *cache;
+	int ret = 0;
 
-int btrfs_free_and_pin_reserved_extent(struct btrfs_fs_info *fs_info,
-				       u64 start, u64 len)
-{
-	return __btrfs_free_reserved_extent(fs_info, start, len, 1, 0);
+	cache = btrfs_lookup_block_group(fs_info, start);
+	if (!cache) {
+		btrfs_err(fs_info, "unable to find block group for %llu", start);
+		return -ENOSPC;
+	}
+
+	ret = pin_down_extent(cache, start, len, 1);
+	btrfs_put_block_group(cache);
+	return ret;
 }
 
 static int alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 2f4802f405a2..e2d30287e2d5 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3043,7 +3043,7 @@ __get_extent_map(struct inode *inode, struct page *page, size_t pg_offset,
 		*em_cached = NULL;
 	}
 
-	em = get_extent(BTRFS_I(inode), page, pg_offset, start, len, 0);
+	em = get_extent(BTRFS_I(inode), page, pg_offset, start, len);
 	if (em_cached && !IS_ERR_OR_NULL(em)) {
 		BUG_ON(*em_cached);
 		refcount_inc(&em->refs);
@@ -3455,11 +3455,6 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 	update_nr_written(wbc, nr_written + 1);
 
 	end = page_end;
-	if (i_size <= start) {
-		btrfs_writepage_endio_finish_ordered(page, start, page_end, 1);
-		goto done;
-	}
-
 	blocksize = inode->i_sb->s_blocksize;
 
 	while (cur <= end) {
@@ -3471,8 +3466,8 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 							     page_end, 1);
 			break;
 		}
-		em = btrfs_get_extent(BTRFS_I(inode), page, pg_offset, cur,
-				     end - cur + 1, 1);
+		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, cur,
+				      end - cur + 1);
 		if (IS_ERR_OR_NULL(em)) {
 			SetPageError(page);
 			ret = PTR_ERR_OR_ZERO(em);
@@ -3497,22 +3492,11 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 		 */
 		if (compressed || block_start == EXTENT_MAP_HOLE ||
 		    block_start == EXTENT_MAP_INLINE) {
-			/*
-			 * end_io notification does not happen here for
-			 * compressed extents
-			 */
-			if (!compressed)
-				btrfs_writepage_endio_finish_ordered(page, cur,
-							    cur + iosize - 1,
-							    1);
-			else if (compressed) {
-				/* we don't want to end_page_writeback on
-				 * a compressed extent.  this happens
-				 * elsewhere
-				 */
+			if (compressed)
 				nr++;
-			}
-
+			else
+				btrfs_writepage_endio_finish_ordered(page, cur,
+							cur + iosize - 1, 1);
 			cur += iosize;
 			pg_offset += iosize;
 			continue;
@@ -3540,7 +3524,6 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 		pg_offset += iosize;
 		nr++;
 	}
-done:
 	*nr_ret = nr;
 	return ret;
 }
@@ -3562,7 +3545,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 	u64 page_end = start + PAGE_SIZE - 1;
 	int ret;
 	int nr = 0;
-	size_t pg_offset = 0;
+	size_t pg_offset;
 	loff_t i_size = i_size_read(inode);
 	unsigned long end_index = i_size >> PAGE_SHIFT;
 	unsigned long nr_written = 0;
@@ -3591,14 +3574,12 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 		flush_dcache_page(page);
 	}
 
-	pg_offset = 0;
-
 	set_page_extent_mapped(page);
 
 	if (!epd->extent_locked) {
 		ret = writepage_delalloc(inode, page, wbc, start, &nr_written);
 		if (ret == 1)
-			goto done_unlocked;
+			return 0;
 		if (ret)
 			goto done;
 	}
@@ -3606,7 +3587,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 	ret = __extent_writepage_io(inode, page, wbc, epd,
 				    i_size, nr_written, &nr);
 	if (ret == 1)
-		goto done_unlocked;
+		return 0;
 
 done:
 	if (nr == 0) {
@@ -3621,9 +3602,6 @@ done:
 	unlock_page(page);
 	ASSERT(ret <= 0);
 	return ret;
-
-done_unlocked:
-	return 0;
 }
 
 void wait_on_extent_buffer_writeback(struct extent_buffer *eb)
@@ -3941,6 +3919,11 @@ int btree_write_cache_pages(struct address_space *mapping,
 	if (wbc->range_cyclic) {
 		index = mapping->writeback_index; /* Start from prev offset */
 		end = -1;
+		/*
+		 * Start from the beginning does not need to cycle over the
+		 * range, mark it as scanned.
+		 */
+		scanned = (index == 0);
 	} else {
 		index = wbc->range_start >> PAGE_SHIFT;
 		end = wbc->range_end >> PAGE_SHIFT;
@@ -3958,7 +3941,6 @@ retry:
 			tag))) {
 		unsigned i;
 
-		scanned = 1;
 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
 
@@ -4087,6 +4069,11 @@ static int extent_write_cache_pages(struct address_space *mapping,
 	if (wbc->range_cyclic) {
 		index = mapping->writeback_index; /* Start from prev offset */
 		end = -1;
+		/*
+		 * Start from the beginning does not need to cycle over the
+		 * range, mark it as scanned.
+		 */
+		scanned = (index == 0);
 	} else {
 		index = wbc->range_start >> PAGE_SHIFT;
 		end = wbc->range_end >> PAGE_SHIFT;
@@ -4120,7 +4107,6 @@ retry:
 						&index, end, tag))) {
 		unsigned i;
 
-		scanned = 1;
 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
 
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index a8551a1f56e2..5d205bbaafdc 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -183,10 +183,8 @@ static inline int extent_compress_type(unsigned long bio_flags)
 struct extent_map_tree;
 
 typedef struct extent_map *(get_extent_t)(struct btrfs_inode *inode,
-					  struct page *page,
-					  size_t pg_offset,
-					  u64 start, u64 len,
-					  int create);
+					  struct page *page, size_t pg_offset,
+					  u64 start, u64 len);
 
 int try_release_extent_mapping(struct page *page, gfp_t mask);
 int try_release_extent_buffer(struct page *page);
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index b1bfdc5c1387..c2f365662d55 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -148,8 +148,19 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
-				   u64 logical_offset, u8 *dst, int dio)
+/**
+ * btrfs_lookup_bio_sums - Look up checksums for a bio.
+ * @inode: inode that the bio is for.
+ * @bio: bio embedded in btrfs_io_bio.
+ * @offset: Unless (u64)-1, look up checksums for this offset in the file.
+ *          If (u64)-1, use the page offsets from the bio instead.
+ * @dst: Buffer of size btrfs_super_csum_size() used to return checksum. If
+ *       NULL, the checksum is returned in btrfs_io_bio(bio)->csum instead.
+ *
+ * Return: BLK_STS_RESOURCE if allocating memory fails, BLK_STS_OK otherwise.
+ */
+blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
+				   u64 offset, u8 *dst)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct bio_vec bvec;
@@ -158,8 +169,8 @@ static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio
 	struct btrfs_csum_item *item = NULL;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	struct btrfs_path *path;
+	const bool page_offsets = (offset == (u64)-1);
 	u8 *csum;
-	u64 offset = 0;
 	u64 item_start_offset = 0;
 	u64 item_last_offset = 0;
 	u64 disk_bytenr;
@@ -205,15 +216,13 @@ static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio
 	}
 
 	disk_bytenr = (u64)bio->bi_iter.bi_sector << 9;
-	if (dio)
-		offset = logical_offset;
 
 	bio_for_each_segment(bvec, bio, iter) {
 		page_bytes_left = bvec.bv_len;
 		if (count)
 			goto next;
 
-		if (!dio)
+		if (page_offsets)
 			offset = page_offset(bvec.bv_page) + bvec.bv_offset;
 		count = btrfs_find_ordered_sum(inode, offset, disk_bytenr,
 					       csum, nblocks);
@@ -274,7 +283,8 @@ found:
 		csum += count * csum_size;
 		nblocks -= count;
 next:
-		while (count--) {
+		while (count > 0) {
+			count--;
 			disk_bytenr += fs_info->sectorsize;
 			offset += fs_info->sectorsize;
 			page_bytes_left -= fs_info->sectorsize;
@@ -285,18 +295,7 @@ next:
 
 	WARN_ON_ONCE(count);
 	btrfs_free_path(path);
-	return 0;
-}
-
-blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
-				   u8 *dst)
-{
-	return __btrfs_lookup_bio_sums(inode, bio, 0, dst, 0);
-}
-
-blk_status_t btrfs_lookup_bio_sums_dio(struct inode *inode, struct bio *bio, u64 offset)
-{
-	return __btrfs_lookup_bio_sums(inode, bio, offset, NULL, 1);
+	return BLK_STS_OK;
 }
 
 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
@@ -483,8 +482,8 @@ blk_status_t btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
 						 - 1);
 
 		for (i = 0; i < nr_sectors; i++) {
-			if (offset >= ordered->file_offset + ordered->len ||
-				offset < ordered->file_offset) {
+			if (offset >= ordered->file_offset + ordered->num_bytes ||
+			    offset < ordered->file_offset) {
 				unsigned long bytes_left;
 
 				sums->len = this_sum_bytes;
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 8d47c76b7bd1..a16da274c9aa 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -477,8 +477,7 @@ static int btrfs_find_new_delalloc_bytes(struct btrfs_inode *inode,
 		u64 em_len;
 		int ret = 0;
 
-		em = btrfs_get_extent(inode, NULL, 0, search_start,
-				      search_len, 0);
+		em = btrfs_get_extent(inode, NULL, 0, search_start, search_len);
 		if (IS_ERR(em))
 			return PTR_ERR(em);
 
@@ -1501,7 +1500,7 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
 		ordered = btrfs_lookup_ordered_range(inode, start_pos,
 						     last_pos - start_pos + 1);
 		if (ordered &&
-		    ordered->file_offset + ordered->len > start_pos &&
+		    ordered->file_offset + ordered->num_bytes > start_pos &&
 		    ordered->file_offset <= last_pos) {
 			unlock_extent_cached(&inode->io_tree, start_pos,
 					last_pos, cached_state);
@@ -2390,7 +2389,7 @@ static int find_first_non_hole(struct inode *inode, u64 *start, u64 *len)
 
 	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0,
 			      round_down(*start, fs_info->sectorsize),
-			      round_up(*len, fs_info->sectorsize), 0);
+			      round_up(*len, fs_info->sectorsize));
 	if (IS_ERR(em))
 		return PTR_ERR(em);
 
@@ -2426,7 +2425,7 @@ static int btrfs_punch_hole_lock_range(struct inode *inode,
 		 * we need to try again.
 		 */
 		if ((!ordered ||
-		    (ordered->file_offset + ordered->len <= lockstart ||
+		    (ordered->file_offset + ordered->num_bytes <= lockstart ||
 		     ordered->file_offset > lockend)) &&
 		     !filemap_range_has_page(inode->i_mapping,
 					     lockstart, lockend)) {
@@ -2957,7 +2956,7 @@ static int btrfs_zero_range_check_range_boundary(struct inode *inode,
 	int ret;
 
 	offset = round_down(offset, sectorsize);
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em))
 		return PTR_ERR(em);
 
@@ -2990,8 +2989,8 @@ static int btrfs_zero_range(struct inode *inode,
 
 	inode_dio_wait(inode);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0,
-			      alloc_start, alloc_end - alloc_start, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, alloc_start,
+			      alloc_end - alloc_start);
 	if (IS_ERR(em)) {
 		ret = PTR_ERR(em);
 		goto out;
@@ -3034,8 +3033,8 @@ static int btrfs_zero_range(struct inode *inode,
 
 	if (BTRFS_BYTES_TO_BLKS(fs_info, offset) ==
 	    BTRFS_BYTES_TO_BLKS(fs_info, offset + len - 1)) {
-		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0,
-				      alloc_start, sectorsize, 0);
+		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, alloc_start,
+				      sectorsize);
 		if (IS_ERR(em)) {
 			ret = PTR_ERR(em);
 			goto out;
@@ -3248,7 +3247,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 		ordered = btrfs_lookup_first_ordered_extent(inode, locked_end);
 
 		if (ordered &&
-		    ordered->file_offset + ordered->len > alloc_start &&
+		    ordered->file_offset + ordered->num_bytes > alloc_start &&
 		    ordered->file_offset < alloc_end) {
 			btrfs_put_ordered_extent(ordered);
 			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
@@ -3273,7 +3272,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 	INIT_LIST_HEAD(&reserve_list);
 	while (cur_offset < alloc_end) {
 		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, cur_offset,
-				      alloc_end - cur_offset, 0);
+				      alloc_end - cur_offset);
 		if (IS_ERR(em)) {
 			ret = PTR_ERR(em);
 			break;
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 3283da419200..0598fd3c6e3f 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -21,9 +21,11 @@
 #include "space-info.h"
 #include "delalloc-space.h"
 #include "block-group.h"
+#include "discard.h"
 
 #define BITS_PER_BITMAP		(PAGE_SIZE * 8UL)
-#define MAX_CACHE_BYTES_PER_GIG	SZ_32K
+#define MAX_CACHE_BYTES_PER_GIG	SZ_64K
+#define FORCE_EXTENT_THRESHOLD	SZ_1M
 
 struct btrfs_trim_range {
 	u64 start;
@@ -31,6 +33,8 @@ struct btrfs_trim_range {
 	struct list_head list;
 };
 
+static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *bitmap_info);
 static int link_free_space(struct btrfs_free_space_ctl *ctl,
 			   struct btrfs_free_space *info);
 static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
@@ -752,6 +756,16 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 			goto free_cache;
 		}
 
+		/*
+		 * Sync discard ensures that the free space cache is always
+		 * trimmed.  So when reading this in, the state should reflect
+		 * that.  We also do this for async as a stop gap for lack of
+		 * persistence.
+		 */
+		if (btrfs_test_opt(fs_info, DISCARD_SYNC) ||
+		    btrfs_test_opt(fs_info, DISCARD_ASYNC))
+			e->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+
 		if (!e->bytes) {
 			kmem_cache_free(btrfs_free_space_cachep, e);
 			goto free_cache;
@@ -805,12 +819,19 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 		ret = io_ctl_read_bitmap(&io_ctl, e);
 		if (ret)
 			goto free_cache;
+		e->bitmap_extents = count_bitmap_extents(ctl, e);
+		if (!btrfs_free_space_trimmed(e)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				e->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += e->bytes;
+		}
 	}
 
 	io_ctl_drop_pages(&io_ctl);
 	merge_space_tree(ctl);
 	ret = 1;
 out:
+	btrfs_discard_update_discardable(ctl->private, ctl);
 	io_ctl_free(&io_ctl);
 	return ret;
 free_cache:
@@ -1624,6 +1645,11 @@ __unlink_free_space(struct btrfs_free_space_ctl *ctl,
 {
 	rb_erase(&info->offset_index, &ctl->free_space_offset);
 	ctl->free_extents--;
+
+	if (!info->bitmap && !btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR]--;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= info->bytes;
+	}
 }
 
 static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
@@ -1644,6 +1670,11 @@ static int link_free_space(struct btrfs_free_space_ctl *ctl,
 	if (ret)
 		return ret;
 
+	if (!info->bitmap && !btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR]++;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] += info->bytes;
+	}
+
 	ctl->free_space += info->bytes;
 	ctl->free_extents++;
 	return ret;
@@ -1664,26 +1695,17 @@ static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
 	ASSERT(ctl->total_bitmaps <= max_bitmaps);
 
 	/*
-	 * The goal is to keep the total amount of memory used per 1gb of space
-	 * at or below 32k, so we need to adjust how much memory we allow to be
-	 * used by extent based free space tracking
+	 * We are trying to keep the total amount of memory used per 1GiB of
+	 * space to be MAX_CACHE_BYTES_PER_GIG.  However, with a reclamation
+	 * mechanism of pulling extents >= FORCE_EXTENT_THRESHOLD out of
+	 * bitmaps, we may end up using more memory than this.
 	 */
 	if (size < SZ_1G)
 		max_bytes = MAX_CACHE_BYTES_PER_GIG;
 	else
 		max_bytes = MAX_CACHE_BYTES_PER_GIG * div_u64(size, SZ_1G);
 
-	/*
-	 * we want to account for 1 more bitmap than what we have so we can make
-	 * sure we don't go over our overall goal of MAX_CACHE_BYTES_PER_GIG as
-	 * we add more bitmaps.
-	 */
-	bitmap_bytes = (ctl->total_bitmaps + 1) * ctl->unit;
-
-	if (bitmap_bytes >= max_bytes) {
-		ctl->extents_thresh = 0;
-		return;
-	}
+	bitmap_bytes = ctl->total_bitmaps * ctl->unit;
 
 	/*
 	 * we want the extent entry threshold to always be at most 1/2 the max
@@ -1700,17 +1722,31 @@ static inline void __bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
 				       struct btrfs_free_space *info,
 				       u64 offset, u64 bytes)
 {
-	unsigned long start, count;
+	unsigned long start, count, end;
+	int extent_delta = -1;
 
 	start = offset_to_bit(info->offset, ctl->unit, offset);
 	count = bytes_to_bits(bytes, ctl->unit);
-	ASSERT(start + count <= BITS_PER_BITMAP);
+	end = start + count;
+	ASSERT(end <= BITS_PER_BITMAP);
 
 	bitmap_clear(info->bitmap, start, count);
 
 	info->bytes -= bytes;
 	if (info->max_extent_size > ctl->unit)
 		info->max_extent_size = 0;
+
+	if (start && test_bit(start - 1, info->bitmap))
+		extent_delta++;
+
+	if (end < BITS_PER_BITMAP && test_bit(end, info->bitmap))
+		extent_delta++;
+
+	info->bitmap_extents += extent_delta;
+	if (!btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bytes;
+	}
 }
 
 static void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
@@ -1725,16 +1761,30 @@ static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
 			    struct btrfs_free_space *info, u64 offset,
 			    u64 bytes)
 {
-	unsigned long start, count;
+	unsigned long start, count, end;
+	int extent_delta = 1;
 
 	start = offset_to_bit(info->offset, ctl->unit, offset);
 	count = bytes_to_bits(bytes, ctl->unit);
-	ASSERT(start + count <= BITS_PER_BITMAP);
+	end = start + count;
+	ASSERT(end <= BITS_PER_BITMAP);
 
 	bitmap_set(info->bitmap, start, count);
 
 	info->bytes += bytes;
 	ctl->free_space += bytes;
+
+	if (start && test_bit(start - 1, info->bitmap))
+		extent_delta--;
+
+	if (end < BITS_PER_BITMAP && test_bit(end, info->bitmap))
+		extent_delta--;
+
+	info->bitmap_extents += extent_delta;
+	if (!btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] += bytes;
+	}
 }
 
 /*
@@ -1870,11 +1920,35 @@ out:
 	return NULL;
 }
 
+static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *bitmap_info)
+{
+	struct btrfs_block_group *block_group = ctl->private;
+	u64 bytes = bitmap_info->bytes;
+	unsigned int rs, re;
+	int count = 0;
+
+	if (!block_group || !bytes)
+		return count;
+
+	bitmap_for_each_set_region(bitmap_info->bitmap, rs, re, 0,
+				   BITS_PER_BITMAP) {
+		bytes -= (rs - re) * ctl->unit;
+		count++;
+
+		if (!bytes)
+			break;
+	}
+
+	return count;
+}
+
 static void add_new_bitmap(struct btrfs_free_space_ctl *ctl,
 			   struct btrfs_free_space *info, u64 offset)
 {
 	info->offset = offset_to_bitmap(ctl, offset);
 	info->bytes = 0;
+	info->bitmap_extents = 0;
 	INIT_LIST_HEAD(&info->list);
 	link_free_space(ctl, info);
 	ctl->total_bitmaps++;
@@ -1885,6 +1959,18 @@ static void add_new_bitmap(struct btrfs_free_space_ctl *ctl,
 static void free_bitmap(struct btrfs_free_space_ctl *ctl,
 			struct btrfs_free_space *bitmap_info)
 {
+	/*
+	 * Normally when this is called, the bitmap is completely empty. However,
+	 * if we are blowing up the free space cache for one reason or another
+	 * via __btrfs_remove_free_space_cache(), then it may not be freed and
+	 * we may leave stats on the table.
+	 */
+	if (bitmap_info->bytes && !btrfs_free_space_trimmed(bitmap_info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR] -=
+			bitmap_info->bitmap_extents;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bitmap_info->bytes;
+
+	}
 	unlink_free_space(ctl, bitmap_info);
 	kmem_cache_free(btrfs_free_space_bitmap_cachep, bitmap_info->bitmap);
 	kmem_cache_free(btrfs_free_space_cachep, bitmap_info);
@@ -1971,11 +2057,24 @@ again:
 
 static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
 			       struct btrfs_free_space *info, u64 offset,
-			       u64 bytes)
+			       u64 bytes, enum btrfs_trim_state trim_state)
 {
 	u64 bytes_to_set = 0;
 	u64 end;
 
+	/*
+	 * This is a tradeoff to make bitmap trim state minimal.  We mark the
+	 * whole bitmap untrimmed if at any point we add untrimmed regions.
+	 */
+	if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED) {
+		if (btrfs_free_space_trimmed(info)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				info->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += info->bytes;
+		}
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	}
+
 	end = info->offset + (u64)(BITS_PER_BITMAP * ctl->unit);
 
 	bytes_to_set = min(end - offset, bytes);
@@ -2004,6 +2103,10 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 		forced = true;
 #endif
 
+	/* This is a way to reclaim large regions from the bitmaps. */
+	if (!forced && info->bytes >= FORCE_EXTENT_THRESHOLD)
+		return false;
+
 	/*
 	 * If we are below the extents threshold then we can add this as an
 	 * extent, and don't have to deal with the bitmap
@@ -2016,8 +2119,8 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 		 * of cache left then go ahead an dadd them, no sense in adding
 		 * the overhead of a bitmap if we don't have to.
 		 */
-		if (info->bytes <= fs_info->sectorsize * 4) {
-			if (ctl->free_extents * 2 <= ctl->extents_thresh)
+		if (info->bytes <= fs_info->sectorsize * 8) {
+			if (ctl->free_extents * 3 <= ctl->extents_thresh)
 				return false;
 		} else {
 			return false;
@@ -2050,10 +2153,12 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
 	struct btrfs_block_group *block_group = NULL;
 	int added = 0;
 	u64 bytes, offset, bytes_added;
+	enum btrfs_trim_state trim_state;
 	int ret;
 
 	bytes = info->bytes;
 	offset = info->offset;
+	trim_state = info->trim_state;
 
 	if (!ctl->op->use_bitmap(ctl, info))
 		return 0;
@@ -2088,8 +2193,8 @@ again:
 		}
 
 		if (entry->offset == offset_to_bitmap(ctl, offset)) {
-			bytes_added = add_bytes_to_bitmap(ctl, entry,
-							  offset, bytes);
+			bytes_added = add_bytes_to_bitmap(ctl, entry, offset,
+							  bytes, trim_state);
 			bytes -= bytes_added;
 			offset += bytes_added;
 		}
@@ -2108,7 +2213,8 @@ no_cluster_bitmap:
 		goto new_bitmap;
 	}
 
-	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+					  trim_state);
 	bytes -= bytes_added;
 	offset += bytes_added;
 	added = 0;
@@ -2142,6 +2248,7 @@ new_bitmap:
 		/* allocate the bitmap */
 		info->bitmap = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep,
 						 GFP_NOFS);
+		info->trim_state = BTRFS_TRIM_STATE_TRIMMED;
 		spin_lock(&ctl->tree_lock);
 		if (!info->bitmap) {
 			ret = -ENOMEM;
@@ -2161,6 +2268,22 @@ out:
 	return ret;
 }
 
+/*
+ * Free space merging rules:
+ *  1) Merge trimmed areas together
+ *  2) Let untrimmed areas coalesce with trimmed areas
+ *  3) Always pull neighboring regions from bitmaps
+ *
+ * The above rules are for when we merge free space based on btrfs_trim_state.
+ * Rules 2 and 3 are subtle because they are suboptimal, but are done for the
+ * same reason: to promote larger extent regions which makes life easier for
+ * find_free_extent().  Rule 2 enables coalescing based on the common path
+ * being returning free space from btrfs_finish_extent_commit().  So when free
+ * space is trimmed, it will prevent aggregating trimmed new region and
+ * untrimmed regions in the rb_tree.  Rule 3 is purely to obtain larger extents
+ * and provide find_free_extent() with the largest extents possible hoping for
+ * the reuse path.
+ */
 static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 			  struct btrfs_free_space *info, bool update_stat)
 {
@@ -2169,6 +2292,7 @@ static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 	bool merged = false;
 	u64 offset = info->offset;
 	u64 bytes = info->bytes;
+	const bool is_trimmed = btrfs_free_space_trimmed(info);
 
 	/*
 	 * first we want to see if there is free space adjacent to the range we
@@ -2182,7 +2306,9 @@ static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 	else
 		left_info = tree_search_offset(ctl, offset - 1, 0, 0);
 
-	if (right_info && !right_info->bitmap) {
+	/* See try_merge_free_space() comment. */
+	if (right_info && !right_info->bitmap &&
+	    (!is_trimmed || btrfs_free_space_trimmed(right_info))) {
 		if (update_stat)
 			unlink_free_space(ctl, right_info);
 		else
@@ -2192,8 +2318,10 @@ static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 		merged = true;
 	}
 
+	/* See try_merge_free_space() comment. */
 	if (left_info && !left_info->bitmap &&
-	    left_info->offset + left_info->bytes == offset) {
+	    left_info->offset + left_info->bytes == offset &&
+	    (!is_trimmed || btrfs_free_space_trimmed(left_info))) {
 		if (update_stat)
 			unlink_free_space(ctl, left_info);
 		else
@@ -2229,6 +2357,10 @@ static bool steal_from_bitmap_to_end(struct btrfs_free_space_ctl *ctl,
 	bytes = (j - i) * ctl->unit;
 	info->bytes += bytes;
 
+	/* See try_merge_free_space() comment. */
+	if (!btrfs_free_space_trimmed(bitmap))
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
 	if (update_stat)
 		bitmap_clear_bits(ctl, bitmap, end, bytes);
 	else
@@ -2282,6 +2414,10 @@ static bool steal_from_bitmap_to_front(struct btrfs_free_space_ctl *ctl,
 	info->offset -= bytes;
 	info->bytes += bytes;
 
+	/* See try_merge_free_space() comment. */
+	if (!btrfs_free_space_trimmed(bitmap))
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
 	if (update_stat)
 		bitmap_clear_bits(ctl, bitmap, info->offset, bytes);
 	else
@@ -2331,10 +2467,13 @@ static void steal_from_bitmap(struct btrfs_free_space_ctl *ctl,
 
 int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 			   struct btrfs_free_space_ctl *ctl,
-			   u64 offset, u64 bytes)
+			   u64 offset, u64 bytes,
+			   enum btrfs_trim_state trim_state)
 {
+	struct btrfs_block_group *block_group = ctl->private;
 	struct btrfs_free_space *info;
 	int ret = 0;
+	u64 filter_bytes = bytes;
 
 	info = kmem_cache_zalloc(btrfs_free_space_cachep, GFP_NOFS);
 	if (!info)
@@ -2342,6 +2481,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 
 	info->offset = offset;
 	info->bytes = bytes;
+	info->trim_state = trim_state;
 	RB_CLEAR_NODE(&info->offset_index);
 
 	spin_lock(&ctl->tree_lock);
@@ -2370,10 +2510,13 @@ link:
 	 */
 	steal_from_bitmap(ctl, info, true);
 
+	filter_bytes = max(filter_bytes, info->bytes);
+
 	ret = link_free_space(ctl, info);
 	if (ret)
 		kmem_cache_free(btrfs_free_space_cachep, info);
 out:
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 
 	if (ret) {
@@ -2381,15 +2524,44 @@ out:
 		ASSERT(ret != -EEXIST);
 	}
 
+	if (trim_state != BTRFS_TRIM_STATE_TRIMMED) {
+		btrfs_discard_check_filter(block_group, filter_bytes);
+		btrfs_discard_queue_work(&fs_info->discard_ctl, block_group);
+	}
+
 	return ret;
 }
 
 int btrfs_add_free_space(struct btrfs_block_group *block_group,
 			 u64 bytenr, u64 size)
 {
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+	if (btrfs_test_opt(block_group->fs_info, DISCARD_SYNC))
+		trim_state = BTRFS_TRIM_STATE_TRIMMED;
+
+	return __btrfs_add_free_space(block_group->fs_info,
+				      block_group->free_space_ctl,
+				      bytenr, size, trim_state);
+}
+
+/*
+ * This is a subtle distinction because when adding free space back in general,
+ * we want it to be added as untrimmed for async. But in the case where we add
+ * it on loading of a block group, we want to consider it trimmed.
+ */
+int btrfs_add_free_space_async_trimmed(struct btrfs_block_group *block_group,
+				       u64 bytenr, u64 size)
+{
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+	if (btrfs_test_opt(block_group->fs_info, DISCARD_SYNC) ||
+	    btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+		trim_state = BTRFS_TRIM_STATE_TRIMMED;
+
 	return __btrfs_add_free_space(block_group->fs_info,
 				      block_group->free_space_ctl,
-				      bytenr, size);
+				      bytenr, size, trim_state);
 }
 
 int btrfs_remove_free_space(struct btrfs_block_group *block_group,
@@ -2464,8 +2636,10 @@ again:
 			}
 			spin_unlock(&ctl->tree_lock);
 
-			ret = btrfs_add_free_space(block_group, offset + bytes,
-						   old_end - (offset + bytes));
+			ret = __btrfs_add_free_space(block_group->fs_info, ctl,
+						     offset + bytes,
+						     old_end - (offset + bytes),
+						     info->trim_state);
 			WARN_ON(ret);
 			goto out;
 		}
@@ -2477,6 +2651,7 @@ again:
 		goto again;
 	}
 out_lock:
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 out:
 	return ret;
@@ -2562,8 +2737,22 @@ __btrfs_return_cluster_to_free_space(
 
 		bitmap = (entry->bitmap != NULL);
 		if (!bitmap) {
+			/* Merging treats extents as if they were new */
+			if (!btrfs_free_space_trimmed(entry)) {
+				ctl->discardable_extents[BTRFS_STAT_CURR]--;
+				ctl->discardable_bytes[BTRFS_STAT_CURR] -=
+					entry->bytes;
+			}
+
 			try_merge_free_space(ctl, entry, false);
 			steal_from_bitmap(ctl, entry, false);
+
+			/* As we insert directly, update these statistics */
+			if (!btrfs_free_space_trimmed(entry)) {
+				ctl->discardable_extents[BTRFS_STAT_CURR]++;
+				ctl->discardable_bytes[BTRFS_STAT_CURR] +=
+					entry->bytes;
+			}
 		}
 		tree_insert_offset(&ctl->free_space_offset,
 				   entry->offset, &entry->offset_index, bitmap);
@@ -2599,6 +2788,8 @@ void __btrfs_remove_free_space_cache(struct btrfs_free_space_ctl *ctl)
 {
 	spin_lock(&ctl->tree_lock);
 	__btrfs_remove_free_space_cache_locked(ctl);
+	if (ctl->private)
+		btrfs_discard_update_discardable(ctl->private, ctl);
 	spin_unlock(&ctl->tree_lock);
 }
 
@@ -2620,20 +2811,55 @@ void btrfs_remove_free_space_cache(struct btrfs_block_group *block_group)
 		cond_resched_lock(&ctl->tree_lock);
 	}
 	__btrfs_remove_free_space_cache_locked(ctl);
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 
 }
 
+/**
+ * btrfs_is_free_space_trimmed - see if everything is trimmed
+ * @block_group: block_group of interest
+ *
+ * Walk @block_group's free space rb_tree to determine if everything is trimmed.
+ */
+bool btrfs_is_free_space_trimmed(struct btrfs_block_group *block_group)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *info;
+	struct rb_node *node;
+	bool ret = true;
+
+	spin_lock(&ctl->tree_lock);
+	node = rb_first(&ctl->free_space_offset);
+
+	while (node) {
+		info = rb_entry(node, struct btrfs_free_space, offset_index);
+
+		if (!btrfs_free_space_trimmed(info)) {
+			ret = false;
+			break;
+		}
+
+		node = rb_next(node);
+	}
+
+	spin_unlock(&ctl->tree_lock);
+	return ret;
+}
+
 u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			       u64 offset, u64 bytes, u64 empty_size,
 			       u64 *max_extent_size)
 {
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space *entry = NULL;
 	u64 bytes_search = bytes + empty_size;
 	u64 ret = 0;
 	u64 align_gap = 0;
 	u64 align_gap_len = 0;
+	enum btrfs_trim_state align_gap_trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 
 	spin_lock(&ctl->tree_lock);
 	entry = find_free_space(ctl, &offset, &bytes_search,
@@ -2644,12 +2870,20 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 	ret = offset;
 	if (entry->bitmap) {
 		bitmap_clear_bits(ctl, entry, offset, bytes);
+
+		if (!btrfs_free_space_trimmed(entry))
+			atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
 		if (!entry->bytes)
 			free_bitmap(ctl, entry);
 	} else {
 		unlink_free_space(ctl, entry);
 		align_gap_len = offset - entry->offset;
 		align_gap = entry->offset;
+		align_gap_trim_state = entry->trim_state;
+
+		if (!btrfs_free_space_trimmed(entry))
+			atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
 
 		entry->offset = offset + bytes;
 		WARN_ON(entry->bytes < bytes + align_gap_len);
@@ -2661,11 +2895,13 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			link_free_space(ctl, entry);
 	}
 out:
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 
 	if (align_gap_len)
 		__btrfs_add_free_space(block_group->fs_info, ctl,
-				       align_gap, align_gap_len);
+				       align_gap, align_gap_len,
+				       align_gap_trim_state);
 	return ret;
 }
 
@@ -2707,6 +2943,8 @@ int btrfs_return_cluster_to_free_space(
 	ret = __btrfs_return_cluster_to_free_space(block_group, cluster);
 	spin_unlock(&ctl->tree_lock);
 
+	btrfs_discard_queue_work(&block_group->fs_info->discard_ctl, block_group);
+
 	/* finally drop our ref */
 	btrfs_put_block_group(block_group);
 	return ret;
@@ -2750,6 +2988,8 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group *block_group,
 			     u64 min_start, u64 *max_extent_size)
 {
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space *entry = NULL;
 	struct rb_node *node;
 	u64 ret = 0;
@@ -2814,7 +3054,12 @@ out:
 
 	spin_lock(&ctl->tree_lock);
 
+	if (!btrfs_free_space_trimmed(entry))
+		atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
 	ctl->free_space -= bytes;
+	if (!entry->bitmap && !btrfs_free_space_trimmed(entry))
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bytes;
 	if (entry->bytes == 0) {
 		ctl->free_extents--;
 		if (entry->bitmap) {
@@ -2822,6 +3067,8 @@ out:
 					entry->bitmap);
 			ctl->total_bitmaps--;
 			ctl->op->recalc_thresholds(ctl);
+		} else if (!btrfs_free_space_trimmed(entry)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR]--;
 		}
 		kmem_cache_free(btrfs_free_space_cachep, entry);
 	}
@@ -3148,6 +3395,7 @@ void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
 static int do_trimming(struct btrfs_block_group *block_group,
 		       u64 *total_trimmed, u64 start, u64 bytes,
 		       u64 reserved_start, u64 reserved_bytes,
+		       enum btrfs_trim_state reserved_trim_state,
 		       struct btrfs_trim_range *trim_entry)
 {
 	struct btrfs_space_info *space_info = block_group->space_info;
@@ -3155,6 +3403,9 @@ static int do_trimming(struct btrfs_block_group *block_group,
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	int ret;
 	int update = 0;
+	const u64 end = start + bytes;
+	const u64 reserved_end = reserved_start + reserved_bytes;
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 	u64 trimmed = 0;
 
 	spin_lock(&space_info->lock);
@@ -3168,11 +3419,20 @@ static int do_trimming(struct btrfs_block_group *block_group,
 	spin_unlock(&space_info->lock);
 
 	ret = btrfs_discard_extent(fs_info, start, bytes, &trimmed);
-	if (!ret)
+	if (!ret) {
 		*total_trimmed += trimmed;
+		trim_state = BTRFS_TRIM_STATE_TRIMMED;
+	}
 
 	mutex_lock(&ctl->cache_writeout_mutex);
-	btrfs_add_free_space(block_group, reserved_start, reserved_bytes);
+	if (reserved_start < start)
+		__btrfs_add_free_space(fs_info, ctl, reserved_start,
+				       start - reserved_start,
+				       reserved_trim_state);
+	if (start + bytes < reserved_start + reserved_bytes)
+		__btrfs_add_free_space(fs_info, ctl, end, reserved_end - end,
+				       reserved_trim_state);
+	__btrfs_add_free_space(fs_info, ctl, start, bytes, trim_state);
 	list_del(&trim_entry->list);
 	mutex_unlock(&ctl->cache_writeout_mutex);
 
@@ -3190,16 +3450,24 @@ static int do_trimming(struct btrfs_block_group *block_group,
 	return ret;
 }
 
+/*
+ * If @async is set, then we will trim 1 region and return.
+ */
 static int trim_no_bitmap(struct btrfs_block_group *block_group,
-			  u64 *total_trimmed, u64 start, u64 end, u64 minlen)
+			  u64 *total_trimmed, u64 start, u64 end, u64 minlen,
+			  bool async)
 {
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	struct btrfs_free_space *entry;
 	struct rb_node *node;
 	int ret = 0;
 	u64 extent_start;
 	u64 extent_bytes;
+	enum btrfs_trim_state extent_trim_state;
 	u64 bytes;
+	const u64 max_discard_size = READ_ONCE(discard_ctl->max_discard_size);
 
 	while (start < end) {
 		struct btrfs_trim_range trim_entry;
@@ -3207,49 +3475,66 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 		mutex_lock(&ctl->cache_writeout_mutex);
 		spin_lock(&ctl->tree_lock);
 
-		if (ctl->free_space < minlen) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			break;
-		}
+		if (ctl->free_space < minlen)
+			goto out_unlock;
 
 		entry = tree_search_offset(ctl, start, 0, 1);
-		if (!entry) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			break;
-		}
+		if (!entry)
+			goto out_unlock;
 
-		/* skip bitmaps */
-		while (entry->bitmap) {
+		/* Skip bitmaps and if async, already trimmed entries */
+		while (entry->bitmap ||
+		       (async && btrfs_free_space_trimmed(entry))) {
 			node = rb_next(&entry->offset_index);
-			if (!node) {
-				spin_unlock(&ctl->tree_lock);
-				mutex_unlock(&ctl->cache_writeout_mutex);
-				goto out;
-			}
+			if (!node)
+				goto out_unlock;
 			entry = rb_entry(node, struct btrfs_free_space,
 					 offset_index);
 		}
 
-		if (entry->offset >= end) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			break;
-		}
+		if (entry->offset >= end)
+			goto out_unlock;
 
 		extent_start = entry->offset;
 		extent_bytes = entry->bytes;
-		start = max(start, extent_start);
-		bytes = min(extent_start + extent_bytes, end) - start;
-		if (bytes < minlen) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			goto next;
-		}
+		extent_trim_state = entry->trim_state;
+		if (async) {
+			start = entry->offset;
+			bytes = entry->bytes;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
+			unlink_free_space(ctl, entry);
+			/*
+			 * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+			 * If X < BTRFS_ASYNC_DISCARD_MIN_FILTER, we won't trim
+			 * X when we come back around.  So trim it now.
+			 */
+			if (max_discard_size &&
+			    bytes >= (max_discard_size +
+				      BTRFS_ASYNC_DISCARD_MIN_FILTER)) {
+				bytes = max_discard_size;
+				extent_bytes = max_discard_size;
+				entry->offset += max_discard_size;
+				entry->bytes -= max_discard_size;
+				link_free_space(ctl, entry);
+			} else {
+				kmem_cache_free(btrfs_free_space_cachep, entry);
+			}
+		} else {
+			start = max(start, extent_start);
+			bytes = min(extent_start + extent_bytes, end) - start;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
 
-		unlink_free_space(ctl, entry);
-		kmem_cache_free(btrfs_free_space_cachep, entry);
+			unlink_free_space(ctl, entry);
+			kmem_cache_free(btrfs_free_space_cachep, entry);
+		}
 
 		spin_unlock(&ctl->tree_lock);
 		trim_entry.start = extent_start;
@@ -3258,11 +3543,17 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 		mutex_unlock(&ctl->cache_writeout_mutex);
 
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
-				  extent_start, extent_bytes, &trim_entry);
-		if (ret)
+				  extent_start, extent_bytes, extent_trim_state,
+				  &trim_entry);
+		if (ret) {
+			block_group->discard_cursor = start + bytes;
 			break;
+		}
 next:
 		start += bytes;
+		block_group->discard_cursor = start;
+		if (async && *total_trimmed)
+			break;
 
 		if (fatal_signal_pending(current)) {
 			ret = -ERESTARTSYS;
@@ -3271,19 +3562,76 @@ next:
 
 		cond_resched();
 	}
-out:
+
+	return ret;
+
+out_unlock:
+	block_group->discard_cursor = btrfs_block_group_end(block_group);
+	spin_unlock(&ctl->tree_lock);
+	mutex_unlock(&ctl->cache_writeout_mutex);
+
 	return ret;
 }
 
+/*
+ * If we break out of trimming a bitmap prematurely, we should reset the
+ * trimming bit.  In a rather contrieved case, it's possible to race here so
+ * reset the state to BTRFS_TRIM_STATE_UNTRIMMED.
+ *
+ * start = start of bitmap
+ * end = near end of bitmap
+ *
+ * Thread 1:			Thread 2:
+ * trim_bitmaps(start)
+ *				trim_bitmaps(end)
+ *				end_trimming_bitmap()
+ * reset_trimming_bitmap()
+ */
+static void reset_trimming_bitmap(struct btrfs_free_space_ctl *ctl, u64 offset)
+{
+	struct btrfs_free_space *entry;
+
+	spin_lock(&ctl->tree_lock);
+	entry = tree_search_offset(ctl, offset, 1, 0);
+	if (entry) {
+		if (btrfs_free_space_trimmed(entry)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				entry->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += entry->bytes;
+		}
+		entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	}
+
+	spin_unlock(&ctl->tree_lock);
+}
+
+static void end_trimming_bitmap(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *entry)
+{
+	if (btrfs_free_space_trimming_bitmap(entry)) {
+		entry->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+		ctl->discardable_extents[BTRFS_STAT_CURR] -=
+			entry->bitmap_extents;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= entry->bytes;
+	}
+}
+
+/*
+ * If @async is set, then we will trim 1 region and return.
+ */
 static int trim_bitmaps(struct btrfs_block_group *block_group,
-			u64 *total_trimmed, u64 start, u64 end, u64 minlen)
+			u64 *total_trimmed, u64 start, u64 end, u64 minlen,
+			u64 maxlen, bool async)
 {
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	struct btrfs_free_space *entry;
 	int ret = 0;
 	int ret2;
 	u64 bytes;
 	u64 offset = offset_to_bitmap(ctl, start);
+	const u64 max_discard_size = READ_ONCE(discard_ctl->max_discard_size);
 
 	while (offset < end) {
 		bool next_bitmap = false;
@@ -3293,35 +3641,84 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		spin_lock(&ctl->tree_lock);
 
 		if (ctl->free_space < minlen) {
+			block_group->discard_cursor =
+				btrfs_block_group_end(block_group);
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			break;
 		}
 
 		entry = tree_search_offset(ctl, offset, 1, 0);
-		if (!entry) {
+		/*
+		 * Bitmaps are marked trimmed lossily now to prevent constant
+		 * discarding of the same bitmap (the reason why we are bound
+		 * by the filters).  So, retrim the block group bitmaps when we
+		 * are preparing to punt to the unused_bgs list.  This uses
+		 * @minlen to determine if we are in BTRFS_DISCARD_INDEX_UNUSED
+		 * which is the only discard index which sets minlen to 0.
+		 */
+		if (!entry || (async && minlen && start == offset &&
+			       btrfs_free_space_trimmed(entry))) {
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			next_bitmap = true;
 			goto next;
 		}
 
+		/*
+		 * Async discard bitmap trimming begins at by setting the start
+		 * to be key.objectid and the offset_to_bitmap() aligns to the
+		 * start of the bitmap.  This lets us know we are fully
+		 * scanning the bitmap rather than only some portion of it.
+		 */
+		if (start == offset)
+			entry->trim_state = BTRFS_TRIM_STATE_TRIMMING;
+
 		bytes = minlen;
 		ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
 		if (ret2 || start >= end) {
+			/*
+			 * We lossily consider a bitmap trimmed if we only skip
+			 * over regions <= BTRFS_ASYNC_DISCARD_MIN_FILTER.
+			 */
+			if (ret2 && minlen <= BTRFS_ASYNC_DISCARD_MIN_FILTER)
+				end_trimming_bitmap(ctl, entry);
+			else
+				entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			next_bitmap = true;
 			goto next;
 		}
 
+		/*
+		 * We already trimmed a region, but are using the locking above
+		 * to reset the trim_state.
+		 */
+		if (async && *total_trimmed) {
+			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
+			goto out;
+		}
+
 		bytes = min(bytes, end - start);
-		if (bytes < minlen) {
+		if (bytes < minlen || (async && maxlen && bytes > maxlen)) {
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			goto next;
 		}
 
+		/*
+		 * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+		 * If X < @minlen, we won't trim X when we come back around.
+		 * So trim it now.  We differ here from trimming extents as we
+		 * don't keep individual state per bit.
+		 */
+		if (async &&
+		    max_discard_size &&
+		    bytes > (max_discard_size + minlen))
+			bytes = max_discard_size;
+
 		bitmap_clear_bits(ctl, entry, start, bytes);
 		if (entry->bytes == 0)
 			free_bitmap(ctl, entry);
@@ -3333,19 +3730,25 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		mutex_unlock(&ctl->cache_writeout_mutex);
 
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
-				  start, bytes, &trim_entry);
-		if (ret)
+				  start, bytes, 0, &trim_entry);
+		if (ret) {
+			reset_trimming_bitmap(ctl, offset);
+			block_group->discard_cursor =
+				btrfs_block_group_end(block_group);
 			break;
+		}
 next:
 		if (next_bitmap) {
 			offset += BITS_PER_BITMAP * ctl->unit;
+			start = offset;
 		} else {
 			start += bytes;
-			if (start >= offset + BITS_PER_BITMAP * ctl->unit)
-				offset += BITS_PER_BITMAP * ctl->unit;
 		}
+		block_group->discard_cursor = start;
 
 		if (fatal_signal_pending(current)) {
+			if (start != offset)
+				reset_trimming_bitmap(ctl, offset);
 			ret = -ERESTARTSYS;
 			break;
 		}
@@ -3353,6 +3756,10 @@ next:
 		cond_resched();
 	}
 
+	if (offset >= end)
+		block_group->discard_cursor = end;
+
+out:
 	return ret;
 }
 
@@ -3399,7 +3806,9 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
 int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 			   u64 *trimmed, u64 start, u64 end, u64 minlen)
 {
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	int ret;
+	u64 rem = 0;
 
 	*trimmed = 0;
 
@@ -3411,16 +3820,66 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 	btrfs_get_block_group_trimming(block_group);
 	spin_unlock(&block_group->lock);
 
-	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen);
+	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, false);
 	if (ret)
 		goto out;
 
-	ret = trim_bitmaps(block_group, trimmed, start, end, minlen);
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, 0, false);
+	div64_u64_rem(end, BITS_PER_BITMAP * ctl->unit, &rem);
+	/* If we ended in the middle of a bitmap, reset the trimming flag */
+	if (rem)
+		reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end));
 out:
 	btrfs_put_block_group_trimming(block_group);
 	return ret;
 }
 
+int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   bool async)
+{
+	int ret;
+
+	*trimmed = 0;
+
+	spin_lock(&block_group->lock);
+	if (block_group->removed) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	btrfs_get_block_group_trimming(block_group);
+	spin_unlock(&block_group->lock);
+
+	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, async);
+	btrfs_put_block_group_trimming(block_group);
+
+	return ret;
+}
+
+int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   u64 maxlen, bool async)
+{
+	int ret;
+
+	*trimmed = 0;
+
+	spin_lock(&block_group->lock);
+	if (block_group->removed) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	btrfs_get_block_group_trimming(block_group);
+	spin_unlock(&block_group->lock);
+
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, maxlen,
+			   async);
+
+	btrfs_put_block_group_trimming(block_group);
+
+	return ret;
+}
+
 /*
  * Find the left-most item in the cache tree, and then return the
  * smallest inode number in the item.
@@ -3600,6 +4059,7 @@ int test_add_free_space_entry(struct btrfs_block_group *cache,
 	struct btrfs_free_space_ctl *ctl = cache->free_space_ctl;
 	struct btrfs_free_space *info = NULL, *bitmap_info;
 	void *map = NULL;
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_TRIMMED;
 	u64 bytes_added;
 	int ret;
 
@@ -3641,7 +4101,8 @@ again:
 		info = NULL;
 	}
 
-	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+					  trim_state);
 
 	bytes -= bytes_added;
 	offset += bytes_added;
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index ba9a23241101..2e0a8077aa74 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -6,6 +6,20 @@
 #ifndef BTRFS_FREE_SPACE_CACHE_H
 #define BTRFS_FREE_SPACE_CACHE_H
 
+/*
+ * This is the trim state of an extent or bitmap.
+ *
+ * BTRFS_TRIM_STATE_TRIMMING is special and used to maintain the state of a
+ * bitmap as we may need several trims to fully trim a single bitmap entry.
+ * This is reset should any free space other than trimmed space be added to the
+ * bitmap.
+ */
+enum btrfs_trim_state {
+	BTRFS_TRIM_STATE_UNTRIMMED,
+	BTRFS_TRIM_STATE_TRIMMED,
+	BTRFS_TRIM_STATE_TRIMMING,
+};
+
 struct btrfs_free_space {
 	struct rb_node offset_index;
 	u64 offset;
@@ -13,8 +27,21 @@ struct btrfs_free_space {
 	u64 max_extent_size;
 	unsigned long *bitmap;
 	struct list_head list;
+	enum btrfs_trim_state trim_state;
+	s32 bitmap_extents;
 };
 
+static inline bool btrfs_free_space_trimmed(struct btrfs_free_space *info)
+{
+	return (info->trim_state == BTRFS_TRIM_STATE_TRIMMED);
+}
+
+static inline bool btrfs_free_space_trimming_bitmap(
+					    struct btrfs_free_space *info)
+{
+	return (info->trim_state == BTRFS_TRIM_STATE_TRIMMING);
+}
+
 struct btrfs_free_space_ctl {
 	spinlock_t tree_lock;
 	struct rb_root free_space_offset;
@@ -24,6 +51,8 @@ struct btrfs_free_space_ctl {
 	int total_bitmaps;
 	int unit;
 	u64 start;
+	s32 discardable_extents[BTRFS_STAT_NR_ENTRIES];
+	s64 discardable_bytes[BTRFS_STAT_NR_ENTRIES];
 	const struct btrfs_free_space_op *op;
 	void *private;
 	struct mutex cache_writeout_mutex;
@@ -83,13 +112,17 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root,
 void btrfs_init_free_space_ctl(struct btrfs_block_group *block_group);
 int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 			   struct btrfs_free_space_ctl *ctl,
-			   u64 bytenr, u64 size);
+			   u64 bytenr, u64 size,
+			   enum btrfs_trim_state trim_state);
 int btrfs_add_free_space(struct btrfs_block_group *block_group,
 			 u64 bytenr, u64 size);
+int btrfs_add_free_space_async_trimmed(struct btrfs_block_group *block_group,
+				       u64 bytenr, u64 size);
 int btrfs_remove_free_space(struct btrfs_block_group *block_group,
 			    u64 bytenr, u64 size);
 void __btrfs_remove_free_space_cache(struct btrfs_free_space_ctl *ctl);
 void btrfs_remove_free_space_cache(struct btrfs_block_group *block_group);
+bool btrfs_is_free_space_trimmed(struct btrfs_block_group *block_group);
 u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			       u64 offset, u64 bytes, u64 empty_size,
 			       u64 *max_extent_size);
@@ -108,6 +141,12 @@ int btrfs_return_cluster_to_free_space(
 			       struct btrfs_free_cluster *cluster);
 int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 			   u64 *trimmed, u64 start, u64 end, u64 minlen);
+int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   bool async);
+int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   u64 maxlen, bool async);
 
 /* Support functions for running our sanity tests */
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 37345fb6191d..d5c9c69d8263 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -107,7 +107,7 @@ again:
 
 		if (last != (u64)-1 && last + 1 != key.objectid) {
 			__btrfs_add_free_space(fs_info, ctl, last + 1,
-					       key.objectid - last - 1);
+					       key.objectid - last - 1, 0);
 			wake_up(&root->ino_cache_wait);
 		}
 
@@ -118,7 +118,7 @@ next:
 
 	if (last < root->highest_objectid - 1) {
 		__btrfs_add_free_space(fs_info, ctl, last + 1,
-				       root->highest_objectid - last - 1);
+				       root->highest_objectid - last - 1, 0);
 	}
 
 	spin_lock(&root->ino_cache_lock);
@@ -175,7 +175,8 @@ static void start_caching(struct btrfs_root *root)
 	ret = btrfs_find_free_objectid(root, &objectid);
 	if (!ret && objectid <= BTRFS_LAST_FREE_OBJECTID) {
 		__btrfs_add_free_space(fs_info, ctl, objectid,
-				       BTRFS_LAST_FREE_OBJECTID - objectid + 1);
+				       BTRFS_LAST_FREE_OBJECTID - objectid + 1,
+				       0);
 		wake_up(&root->ino_cache_wait);
 	}
 
@@ -221,7 +222,7 @@ void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
 		return;
 again:
 	if (root->ino_cache_state == BTRFS_CACHE_FINISHED) {
-		__btrfs_add_free_space(fs_info, pinned, objectid, 1);
+		__btrfs_add_free_space(fs_info, pinned, objectid, 1, 0);
 	} else {
 		down_write(&fs_info->commit_root_sem);
 		spin_lock(&root->ino_cache_lock);
@@ -234,7 +235,7 @@ again:
 
 		start_caching(root);
 
-		__btrfs_add_free_space(fs_info, pinned, objectid, 1);
+		__btrfs_add_free_space(fs_info, pinned, objectid, 1, 0);
 
 		up_write(&fs_info->commit_root_sem);
 	}
@@ -281,7 +282,7 @@ void btrfs_unpin_free_ino(struct btrfs_root *root)
 		spin_unlock(rbroot_lock);
 		if (count)
 			__btrfs_add_free_space(root->fs_info, ctl,
-					       info->offset, count);
+					       info->offset, count, 0);
 		kmem_cache_free(btrfs_free_space_cachep, info);
 	}
 }
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c70baafb2a39..6d2bb58d277a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -44,7 +44,6 @@
 #include "locking.h"
 #include "free-space-cache.h"
 #include "inode-map.h"
-#include "backref.h"
 #include "props.h"
 #include "qgroup.h"
 #include "delalloc-space.h"
@@ -64,7 +63,6 @@ struct btrfs_dio_data {
 
 static const struct inode_operations btrfs_dir_inode_operations;
 static const struct inode_operations btrfs_symlink_inode_operations;
-static const struct inode_operations btrfs_dir_ro_inode_operations;
 static const struct inode_operations btrfs_special_inode_operations;
 static const struct inode_operations btrfs_file_inode_operations;
 static const struct address_space_operations btrfs_aops;
@@ -2128,7 +2126,7 @@ static blk_status_t btrfs_submit_bio_hook(struct inode *inode, struct bio *bio,
 							   bio_flags);
 			goto out;
 		} else if (!skip_sum) {
-			ret = btrfs_lookup_bio_sums(inode, bio, NULL);
+			ret = btrfs_lookup_bio_sums(inode, bio, (u64)-1, NULL);
 			if (ret)
 				goto out;
 		}
@@ -2394,649 +2392,6 @@ out:
 	return ret;
 }
 
-/* snapshot-aware defrag */
-struct sa_defrag_extent_backref {
-	struct rb_node node;
-	struct old_sa_defrag_extent *old;
-	u64 root_id;
-	u64 inum;
-	u64 file_pos;
-	u64 extent_offset;
-	u64 num_bytes;
-	u64 generation;
-};
-
-struct old_sa_defrag_extent {
-	struct list_head list;
-	struct new_sa_defrag_extent *new;
-
-	u64 extent_offset;
-	u64 bytenr;
-	u64 offset;
-	u64 len;
-	int count;
-};
-
-struct new_sa_defrag_extent {
-	struct rb_root root;
-	struct list_head head;
-	struct btrfs_path *path;
-	struct inode *inode;
-	u64 file_pos;
-	u64 len;
-	u64 bytenr;
-	u64 disk_len;
-	u8 compress_type;
-};
-
-static int backref_comp(struct sa_defrag_extent_backref *b1,
-			struct sa_defrag_extent_backref *b2)
-{
-	if (b1->root_id < b2->root_id)
-		return -1;
-	else if (b1->root_id > b2->root_id)
-		return 1;
-
-	if (b1->inum < b2->inum)
-		return -1;
-	else if (b1->inum > b2->inum)
-		return 1;
-
-	if (b1->file_pos < b2->file_pos)
-		return -1;
-	else if (b1->file_pos > b2->file_pos)
-		return 1;
-
-	/*
-	 * [------------------------------] ===> (a range of space)
-	 *     |<--->|   |<---->| =============> (fs/file tree A)
-	 * |<---------------------------->| ===> (fs/file tree B)
-	 *
-	 * A range of space can refer to two file extents in one tree while
-	 * refer to only one file extent in another tree.
-	 *
-	 * So we may process a disk offset more than one time(two extents in A)
-	 * and locate at the same extent(one extent in B), then insert two same
-	 * backrefs(both refer to the extent in B).
-	 */
-	return 0;
-}
-
-static void backref_insert(struct rb_root *root,
-			   struct sa_defrag_extent_backref *backref)
-{
-	struct rb_node **p = &root->rb_node;
-	struct rb_node *parent = NULL;
-	struct sa_defrag_extent_backref *entry;
-	int ret;
-
-	while (*p) {
-		parent = *p;
-		entry = rb_entry(parent, struct sa_defrag_extent_backref, node);
-
-		ret = backref_comp(backref, entry);
-		if (ret < 0)
-			p = &(*p)->rb_left;
-		else
-			p = &(*p)->rb_right;
-	}
-
-	rb_link_node(&backref->node, parent, p);
-	rb_insert_color(&backref->node, root);
-}
-
-/*
- * Note the backref might has changed, and in this case we just return 0.
- */
-static noinline int record_one_backref(u64 inum, u64 offset, u64 root_id,
-				       void *ctx)
-{
-	struct btrfs_file_extent_item *extent;
-	struct old_sa_defrag_extent *old = ctx;
-	struct new_sa_defrag_extent *new = old->new;
-	struct btrfs_path *path = new->path;
-	struct btrfs_key key;
-	struct btrfs_root *root;
-	struct sa_defrag_extent_backref *backref;
-	struct extent_buffer *leaf;
-	struct inode *inode = new->inode;
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	int slot;
-	int ret;
-	u64 extent_offset;
-	u64 num_bytes;
-
-	if (BTRFS_I(inode)->root->root_key.objectid == root_id &&
-	    inum == btrfs_ino(BTRFS_I(inode)))
-		return 0;
-
-	key.objectid = root_id;
-	key.type = BTRFS_ROOT_ITEM_KEY;
-	key.offset = (u64)-1;
-
-	root = btrfs_read_fs_root_no_name(fs_info, &key);
-	if (IS_ERR(root)) {
-		if (PTR_ERR(root) == -ENOENT)
-			return 0;
-		WARN_ON(1);
-		btrfs_debug(fs_info, "inum=%llu, offset=%llu, root_id=%llu",
-			 inum, offset, root_id);
-		return PTR_ERR(root);
-	}
-
-	key.objectid = inum;
-	key.type = BTRFS_EXTENT_DATA_KEY;
-	if (offset > (u64)-1 << 32)
-		key.offset = 0;
-	else
-		key.offset = offset;
-
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (WARN_ON(ret < 0))
-		return ret;
-	ret = 0;
-
-	while (1) {
-		cond_resched();
-
-		leaf = path->nodes[0];
-		slot = path->slots[0];
-
-		if (slot >= btrfs_header_nritems(leaf)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0) {
-				goto out;
-			} else if (ret > 0) {
-				ret = 0;
-				goto out;
-			}
-			continue;
-		}
-
-		path->slots[0]++;
-
-		btrfs_item_key_to_cpu(leaf, &key, slot);
-
-		if (key.objectid > inum)
-			goto out;
-
-		if (key.objectid < inum || key.type != BTRFS_EXTENT_DATA_KEY)
-			continue;
-
-		extent = btrfs_item_ptr(leaf, slot,
-					struct btrfs_file_extent_item);
-
-		if (btrfs_file_extent_disk_bytenr(leaf, extent) != old->bytenr)
-			continue;
-
-		/*
-		 * 'offset' refers to the exact key.offset,
-		 * NOT the 'offset' field in btrfs_extent_data_ref, ie.
-		 * (key.offset - extent_offset).
-		 */
-		if (key.offset != offset)
-			continue;
-
-		extent_offset = btrfs_file_extent_offset(leaf, extent);
-		num_bytes = btrfs_file_extent_num_bytes(leaf, extent);
-
-		if (extent_offset >= old->extent_offset + old->offset +
-		    old->len || extent_offset + num_bytes <=
-		    old->extent_offset + old->offset)
-			continue;
-		break;
-	}
-
-	backref = kmalloc(sizeof(*backref), GFP_NOFS);
-	if (!backref) {
-		ret = -ENOENT;
-		goto out;
-	}
-
-	backref->root_id = root_id;
-	backref->inum = inum;
-	backref->file_pos = offset;
-	backref->num_bytes = num_bytes;
-	backref->extent_offset = extent_offset;
-	backref->generation = btrfs_file_extent_generation(leaf, extent);
-	backref->old = old;
-	backref_insert(&new->root, backref);
-	old->count++;
-out:
-	btrfs_release_path(path);
-	WARN_ON(ret);
-	return ret;
-}
-
-static noinline bool record_extent_backrefs(struct btrfs_path *path,
-				   struct new_sa_defrag_extent *new)
-{
-	struct btrfs_fs_info *fs_info = btrfs_sb(new->inode->i_sb);
-	struct old_sa_defrag_extent *old, *tmp;
-	int ret;
-
-	new->path = path;
-
-	list_for_each_entry_safe(old, tmp, &new->head, list) {
-		ret = iterate_inodes_from_logical(old->bytenr +
-						  old->extent_offset, fs_info,
-						  path, record_one_backref,
-						  old, false);
-		if (ret < 0 && ret != -ENOENT)
-			return false;
-
-		/* no backref to be processed for this extent */
-		if (!old->count) {
-			list_del(&old->list);
-			kfree(old);
-		}
-	}
-
-	if (list_empty(&new->head))
-		return false;
-
-	return true;
-}
-
-static int relink_is_mergable(struct extent_buffer *leaf,
-			      struct btrfs_file_extent_item *fi,
-			      struct new_sa_defrag_extent *new)
-{
-	if (btrfs_file_extent_disk_bytenr(leaf, fi) != new->bytenr)
-		return 0;
-
-	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG)
-		return 0;
-
-	if (btrfs_file_extent_compression(leaf, fi) != new->compress_type)
-		return 0;
-
-	if (btrfs_file_extent_encryption(leaf, fi) ||
-	    btrfs_file_extent_other_encoding(leaf, fi))
-		return 0;
-
-	return 1;
-}
-
-/*
- * Note the backref might has changed, and in this case we just return 0.
- */
-static noinline int relink_extent_backref(struct btrfs_path *path,
-				 struct sa_defrag_extent_backref *prev,
-				 struct sa_defrag_extent_backref *backref)
-{
-	struct btrfs_file_extent_item *extent;
-	struct btrfs_file_extent_item *item;
-	struct btrfs_ordered_extent *ordered;
-	struct btrfs_trans_handle *trans;
-	struct btrfs_ref ref = { 0 };
-	struct btrfs_root *root;
-	struct btrfs_key key;
-	struct extent_buffer *leaf;
-	struct old_sa_defrag_extent *old = backref->old;
-	struct new_sa_defrag_extent *new = old->new;
-	struct btrfs_fs_info *fs_info = btrfs_sb(new->inode->i_sb);
-	struct inode *inode;
-	struct extent_state *cached = NULL;
-	int ret = 0;
-	u64 start;
-	u64 len;
-	u64 lock_start;
-	u64 lock_end;
-	bool merge = false;
-	int index;
-
-	if (prev && prev->root_id == backref->root_id &&
-	    prev->inum == backref->inum &&
-	    prev->file_pos + prev->num_bytes == backref->file_pos)
-		merge = true;
-
-	/* step 1: get root */
-	key.objectid = backref->root_id;
-	key.type = BTRFS_ROOT_ITEM_KEY;
-	key.offset = (u64)-1;
-
-	index = srcu_read_lock(&fs_info->subvol_srcu);
-
-	root = btrfs_read_fs_root_no_name(fs_info, &key);
-	if (IS_ERR(root)) {
-		srcu_read_unlock(&fs_info->subvol_srcu, index);
-		if (PTR_ERR(root) == -ENOENT)
-			return 0;
-		return PTR_ERR(root);
-	}
-
-	if (btrfs_root_readonly(root)) {
-		srcu_read_unlock(&fs_info->subvol_srcu, index);
-		return 0;
-	}
-
-	/* step 2: get inode */
-	key.objectid = backref->inum;
-	key.type = BTRFS_INODE_ITEM_KEY;
-	key.offset = 0;
-
-	inode = btrfs_iget(fs_info->sb, &key, root);
-	if (IS_ERR(inode)) {
-		srcu_read_unlock(&fs_info->subvol_srcu, index);
-		return 0;
-	}
-
-	srcu_read_unlock(&fs_info->subvol_srcu, index);
-
-	/* step 3: relink backref */
-	lock_start = backref->file_pos;
-	lock_end = backref->file_pos + backref->num_bytes - 1;
-	lock_extent_bits(&BTRFS_I(inode)->io_tree, lock_start, lock_end,
-			 &cached);
-
-	ordered = btrfs_lookup_first_ordered_extent(inode, lock_end);
-	if (ordered) {
-		btrfs_put_ordered_extent(ordered);
-		goto out_unlock;
-	}
-
-	trans = btrfs_join_transaction(root);
-	if (IS_ERR(trans)) {
-		ret = PTR_ERR(trans);
-		goto out_unlock;
-	}
-
-	key.objectid = backref->inum;
-	key.type = BTRFS_EXTENT_DATA_KEY;
-	key.offset = backref->file_pos;
-
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0) {
-		goto out_free_path;
-	} else if (ret > 0) {
-		ret = 0;
-		goto out_free_path;
-	}
-
-	extent = btrfs_item_ptr(path->nodes[0], path->slots[0],
-				struct btrfs_file_extent_item);
-
-	if (btrfs_file_extent_generation(path->nodes[0], extent) !=
-	    backref->generation)
-		goto out_free_path;
-
-	btrfs_release_path(path);
-
-	start = backref->file_pos;
-	if (backref->extent_offset < old->extent_offset + old->offset)
-		start += old->extent_offset + old->offset -
-			 backref->extent_offset;
-
-	len = min(backref->extent_offset + backref->num_bytes,
-		  old->extent_offset + old->offset + old->len);
-	len -= max(backref->extent_offset, old->extent_offset + old->offset);
-
-	ret = btrfs_drop_extents(trans, root, inode, start,
-				 start + len, 1);
-	if (ret)
-		goto out_free_path;
-again:
-	key.objectid = btrfs_ino(BTRFS_I(inode));
-	key.type = BTRFS_EXTENT_DATA_KEY;
-	key.offset = start;
-
-	path->leave_spinning = 1;
-	if (merge) {
-		struct btrfs_file_extent_item *fi;
-		u64 extent_len;
-		struct btrfs_key found_key;
-
-		ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
-		if (ret < 0)
-			goto out_free_path;
-
-		path->slots[0]--;
-		leaf = path->nodes[0];
-		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-
-		fi = btrfs_item_ptr(leaf, path->slots[0],
-				    struct btrfs_file_extent_item);
-		extent_len = btrfs_file_extent_num_bytes(leaf, fi);
-
-		if (extent_len + found_key.offset == start &&
-		    relink_is_mergable(leaf, fi, new)) {
-			btrfs_set_file_extent_num_bytes(leaf, fi,
-							extent_len + len);
-			btrfs_mark_buffer_dirty(leaf);
-			inode_add_bytes(inode, len);
-
-			ret = 1;
-			goto out_free_path;
-		} else {
-			merge = false;
-			btrfs_release_path(path);
-			goto again;
-		}
-	}
-
-	ret = btrfs_insert_empty_item(trans, root, path, &key,
-					sizeof(*extent));
-	if (ret) {
-		btrfs_abort_transaction(trans, ret);
-		goto out_free_path;
-	}
-
-	leaf = path->nodes[0];
-	item = btrfs_item_ptr(leaf, path->slots[0],
-				struct btrfs_file_extent_item);
-	btrfs_set_file_extent_disk_bytenr(leaf, item, new->bytenr);
-	btrfs_set_file_extent_disk_num_bytes(leaf, item, new->disk_len);
-	btrfs_set_file_extent_offset(leaf, item, start - new->file_pos);
-	btrfs_set_file_extent_num_bytes(leaf, item, len);
-	btrfs_set_file_extent_ram_bytes(leaf, item, new->len);
-	btrfs_set_file_extent_generation(leaf, item, trans->transid);
-	btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
-	btrfs_set_file_extent_compression(leaf, item, new->compress_type);
-	btrfs_set_file_extent_encryption(leaf, item, 0);
-	btrfs_set_file_extent_other_encoding(leaf, item, 0);
-
-	btrfs_mark_buffer_dirty(leaf);
-	inode_add_bytes(inode, len);
-	btrfs_release_path(path);
-
-	btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new->bytenr,
-			       new->disk_len, 0);
-	btrfs_init_data_ref(&ref, backref->root_id, backref->inum,
-			    new->file_pos);  /* start - extent_offset */
-	ret = btrfs_inc_extent_ref(trans, &ref);
-	if (ret) {
-		btrfs_abort_transaction(trans, ret);
-		goto out_free_path;
-	}
-
-	ret = 1;
-out_free_path:
-	btrfs_release_path(path);
-	path->leave_spinning = 0;
-	btrfs_end_transaction(trans);
-out_unlock:
-	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lock_start, lock_end,
-			     &cached);
-	iput(inode);
-	return ret;
-}
-
-static void free_sa_defrag_extent(struct new_sa_defrag_extent *new)
-{
-	struct old_sa_defrag_extent *old, *tmp;
-
-	if (!new)
-		return;
-
-	list_for_each_entry_safe(old, tmp, &new->head, list) {
-		kfree(old);
-	}
-	kfree(new);
-}
-
-static void relink_file_extents(struct new_sa_defrag_extent *new)
-{
-	struct btrfs_fs_info *fs_info = btrfs_sb(new->inode->i_sb);
-	struct btrfs_path *path;
-	struct sa_defrag_extent_backref *backref;
-	struct sa_defrag_extent_backref *prev = NULL;
-	struct rb_node *node;
-	int ret;
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return;
-
-	if (!record_extent_backrefs(path, new)) {
-		btrfs_free_path(path);
-		goto out;
-	}
-	btrfs_release_path(path);
-
-	while (1) {
-		node = rb_first(&new->root);
-		if (!node)
-			break;
-		rb_erase(node, &new->root);
-
-		backref = rb_entry(node, struct sa_defrag_extent_backref, node);
-
-		ret = relink_extent_backref(path, prev, backref);
-		WARN_ON(ret < 0);
-
-		kfree(prev);
-
-		if (ret == 1)
-			prev = backref;
-		else
-			prev = NULL;
-		cond_resched();
-	}
-	kfree(prev);
-
-	btrfs_free_path(path);
-out:
-	free_sa_defrag_extent(new);
-
-	atomic_dec(&fs_info->defrag_running);
-	wake_up(&fs_info->transaction_wait);
-}
-
-static struct new_sa_defrag_extent *
-record_old_file_extents(struct inode *inode,
-			struct btrfs_ordered_extent *ordered)
-{
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct btrfs_path *path;
-	struct btrfs_key key;
-	struct old_sa_defrag_extent *old;
-	struct new_sa_defrag_extent *new;
-	int ret;
-
-	new = kmalloc(sizeof(*new), GFP_NOFS);
-	if (!new)
-		return NULL;
-
-	new->inode = inode;
-	new->file_pos = ordered->file_offset;
-	new->len = ordered->len;
-	new->bytenr = ordered->start;
-	new->disk_len = ordered->disk_len;
-	new->compress_type = ordered->compress_type;
-	new->root = RB_ROOT;
-	INIT_LIST_HEAD(&new->head);
-
-	path = btrfs_alloc_path();
-	if (!path)
-		goto out_kfree;
-
-	key.objectid = btrfs_ino(BTRFS_I(inode));
-	key.type = BTRFS_EXTENT_DATA_KEY;
-	key.offset = new->file_pos;
-
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out_free_path;
-	if (ret > 0 && path->slots[0] > 0)
-		path->slots[0]--;
-
-	/* find out all the old extents for the file range */
-	while (1) {
-		struct btrfs_file_extent_item *extent;
-		struct extent_buffer *l;
-		int slot;
-		u64 num_bytes;
-		u64 offset;
-		u64 end;
-		u64 disk_bytenr;
-		u64 extent_offset;
-
-		l = path->nodes[0];
-		slot = path->slots[0];
-
-		if (slot >= btrfs_header_nritems(l)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto out_free_path;
-			else if (ret > 0)
-				break;
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(l, &key, slot);
-
-		if (key.objectid != btrfs_ino(BTRFS_I(inode)))
-			break;
-		if (key.type != BTRFS_EXTENT_DATA_KEY)
-			break;
-		if (key.offset >= new->file_pos + new->len)
-			break;
-
-		extent = btrfs_item_ptr(l, slot, struct btrfs_file_extent_item);
-
-		num_bytes = btrfs_file_extent_num_bytes(l, extent);
-		if (key.offset + num_bytes < new->file_pos)
-			goto next;
-
-		disk_bytenr = btrfs_file_extent_disk_bytenr(l, extent);
-		if (!disk_bytenr)
-			goto next;
-
-		extent_offset = btrfs_file_extent_offset(l, extent);
-
-		old = kmalloc(sizeof(*old), GFP_NOFS);
-		if (!old)
-			goto out_free_path;
-
-		offset = max(new->file_pos, key.offset);
-		end = min(new->file_pos + new->len, key.offset + num_bytes);
-
-		old->bytenr = disk_bytenr;
-		old->extent_offset = extent_offset;
-		old->offset = offset - key.offset;
-		old->len = end - offset;
-		old->new = new;
-		old->count = 0;
-		list_add_tail(&old->list, &new->head);
-next:
-		path->slots[0]++;
-		cond_resched();
-	}
-
-	btrfs_free_path(path);
-	atomic_inc(&fs_info->defrag_running);
-
-	return new;
-
-out_free_path:
-	btrfs_free_path(path);
-out_kfree:
-	free_sa_defrag_extent(new);
-	return NULL;
-}
-
 static void btrfs_release_delalloc_bytes(struct btrfs_fs_info *fs_info,
 					 u64 start, u64 len)
 {
@@ -3064,15 +2419,19 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 	struct btrfs_trans_handle *trans = NULL;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	struct extent_state *cached_state = NULL;
-	struct new_sa_defrag_extent *new = NULL;
+	u64 start, end;
 	int compress_type = 0;
 	int ret = 0;
-	u64 logical_len = ordered_extent->len;
+	u64 logical_len = ordered_extent->num_bytes;
 	bool freespace_inode;
 	bool truncated = false;
 	bool range_locked = false;
 	bool clear_new_delalloc_bytes = false;
 	bool clear_reserved_extent = true;
+	unsigned int clear_bits;
+
+	start = ordered_extent->file_offset;
+	end = start + ordered_extent->num_bytes - 1;
 
 	if (!test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
 	    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags) &&
@@ -3086,10 +2445,7 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 		goto out;
 	}
 
-	btrfs_free_io_failure_record(BTRFS_I(inode),
-			ordered_extent->file_offset,
-			ordered_extent->file_offset +
-			ordered_extent->len - 1);
+	btrfs_free_io_failure_record(BTRFS_I(inode), start, end);
 
 	if (test_bit(BTRFS_ORDERED_TRUNCATED, &ordered_extent->flags)) {
 		truncated = true;
@@ -3107,8 +2463,8 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 		 * space for NOCOW range.
 		 * As NOCOW won't cause a new delayed ref, just free the space
 		 */
-		btrfs_qgroup_free_data(inode, NULL, ordered_extent->file_offset,
-				       ordered_extent->len);
+		btrfs_qgroup_free_data(inode, NULL, start,
+				       ordered_extent->num_bytes);
 		btrfs_ordered_update_i_size(inode, 0, ordered_extent);
 		if (freespace_inode)
 			trans = btrfs_join_transaction_spacecache(root);
@@ -3127,23 +2483,7 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 	}
 
 	range_locked = true;
-	lock_extent_bits(io_tree, ordered_extent->file_offset,
-			 ordered_extent->file_offset + ordered_extent->len - 1,
-			 &cached_state);
-
-	ret = test_range_bit(io_tree, ordered_extent->file_offset,
-			ordered_extent->file_offset + ordered_extent->len - 1,
-			EXTENT_DEFRAG, 0, cached_state);
-	if (ret) {
-		u64 last_snapshot = btrfs_root_last_snapshot(&root->root_item);
-		if (0 && last_snapshot >= BTRFS_I(inode)->generation)
-			/* the inode is shared */
-			new = record_old_file_extents(inode, ordered_extent);
-
-		clear_extent_bit(io_tree, ordered_extent->file_offset,
-			ordered_extent->file_offset + ordered_extent->len - 1,
-			EXTENT_DEFRAG, 0, 0, &cached_state);
-	}
+	lock_extent_bits(io_tree, start, end, &cached_state);
 
 	if (freespace_inode)
 		trans = btrfs_join_transaction_spacecache(root);
@@ -3161,31 +2501,30 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 		compress_type = ordered_extent->compress_type;
 	if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
 		BUG_ON(compress_type);
-		btrfs_qgroup_free_data(inode, NULL, ordered_extent->file_offset,
-				       ordered_extent->len);
+		btrfs_qgroup_free_data(inode, NULL, start,
+				       ordered_extent->num_bytes);
 		ret = btrfs_mark_extent_written(trans, BTRFS_I(inode),
 						ordered_extent->file_offset,
 						ordered_extent->file_offset +
 						logical_len);
 	} else {
 		BUG_ON(root == fs_info->tree_root);
-		ret = insert_reserved_file_extent(trans, inode,
-						ordered_extent->file_offset,
-						ordered_extent->start,
-						ordered_extent->disk_len,
+		ret = insert_reserved_file_extent(trans, inode, start,
+						ordered_extent->disk_bytenr,
+						ordered_extent->disk_num_bytes,
 						logical_len, logical_len,
 						compress_type, 0, 0,
 						BTRFS_FILE_EXTENT_REG);
 		if (!ret) {
 			clear_reserved_extent = false;
 			btrfs_release_delalloc_bytes(fs_info,
-						     ordered_extent->start,
-						     ordered_extent->disk_len);
+						ordered_extent->disk_bytenr,
+						ordered_extent->disk_num_bytes);
 		}
 	}
 	unpin_extent_cache(&BTRFS_I(inode)->extent_tree,
-			   ordered_extent->file_offset, ordered_extent->len,
-			   trans->transid);
+			   ordered_extent->file_offset,
+			   ordered_extent->num_bytes, trans->transid);
 	if (ret < 0) {
 		btrfs_abort_transaction(trans, ret);
 		goto out;
@@ -3205,37 +2544,27 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 	}
 	ret = 0;
 out:
-	if (range_locked || clear_new_delalloc_bytes) {
-		unsigned int clear_bits = 0;
-
-		if (range_locked)
-			clear_bits |= EXTENT_LOCKED;
-		if (clear_new_delalloc_bytes)
-			clear_bits |= EXTENT_DELALLOC_NEW;
-		clear_extent_bit(&BTRFS_I(inode)->io_tree,
-				 ordered_extent->file_offset,
-				 ordered_extent->file_offset +
-				 ordered_extent->len - 1,
-				 clear_bits,
-				 (clear_bits & EXTENT_LOCKED) ? 1 : 0,
-				 0, &cached_state);
-	}
+	clear_bits = EXTENT_DEFRAG;
+	if (range_locked)
+		clear_bits |= EXTENT_LOCKED;
+	if (clear_new_delalloc_bytes)
+		clear_bits |= EXTENT_DELALLOC_NEW;
+	clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, clear_bits,
+			 (clear_bits & EXTENT_LOCKED) ? 1 : 0, 0,
+			 &cached_state);
 
 	if (trans)
 		btrfs_end_transaction(trans);
 
 	if (ret || truncated) {
-		u64 start, end;
+		u64 unwritten_start = start;
 
 		if (truncated)
-			start = ordered_extent->file_offset + logical_len;
-		else
-			start = ordered_extent->file_offset;
-		end = ordered_extent->file_offset + ordered_extent->len - 1;
-		clear_extent_uptodate(io_tree, start, end, NULL);
+			unwritten_start += logical_len;
+		clear_extent_uptodate(io_tree, unwritten_start, end, NULL);
 
 		/* Drop the cache for the part of the extent we didn't write. */
-		btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
+		btrfs_drop_extent_cache(BTRFS_I(inode), unwritten_start, end, 0);
 
 		/*
 		 * If the ordered extent had an IOERR or something else went
@@ -3250,29 +2579,28 @@ out:
 		if ((ret || !logical_len) &&
 		    clear_reserved_extent &&
 		    !test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
-		    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags))
+		    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
+			/*
+			 * Discard the range before returning it back to the
+			 * free space pool
+			 */
+			if (ret && btrfs_test_opt(fs_info, DISCARD_SYNC))
+				btrfs_discard_extent(fs_info,
+						ordered_extent->disk_bytenr,
+						ordered_extent->disk_num_bytes,
+						NULL);
 			btrfs_free_reserved_extent(fs_info,
-						   ordered_extent->start,
-						   ordered_extent->disk_len, 1);
+					ordered_extent->disk_bytenr,
+					ordered_extent->disk_num_bytes, 1);
+		}
 	}
 
-
 	/*
 	 * This needs to be done to make sure anybody waiting knows we are done
 	 * updating everything for this ordered extent.
 	 */
 	btrfs_remove_ordered_extent(inode, ordered_extent);
 
-	/* for snapshot-aware defrag */
-	if (new) {
-		if (ret) {
-			free_sa_defrag_extent(new);
-			atomic_dec(&fs_info->defrag_running);
-		} else {
-			relink_file_extents(new);
-		}
-	}
-
 	/* once for us */
 	btrfs_put_ordered_extent(ordered_extent);
 	/* once for the tree */
@@ -5176,7 +4504,7 @@ int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size)
 	cur_offset = hole_start;
 	while (1) {
 		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, cur_offset,
-				block_end - cur_offset, 0);
+				      block_end - cur_offset);
 		if (IS_ERR(em)) {
 			err = PTR_ERR(em);
 			em = NULL;
@@ -5860,7 +5188,11 @@ static struct inode *new_simple_dir(struct super_block *s,
 	set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
 
 	inode->i_ino = BTRFS_EMPTY_SUBVOL_DIR_OBJECTID;
-	inode->i_op = &btrfs_dir_ro_inode_operations;
+	/*
+	 * We only need lookup, the rest is read-only and there's no inode
+	 * associated with the dentry
+	 */
+	inode->i_op = &simple_dir_inode_operations;
 	inode->i_opflags &= ~IOP_XATTR;
 	inode->i_fop = &simple_dir_operations;
 	inode->i_mode = S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO;
@@ -6951,18 +6283,27 @@ static noinline int uncompress_inline(struct btrfs_path *path,
 	return ret;
 }
 
-/*
- * a bit scary, this does extent mapping from logical file offset to the disk.
- * the ugly parts come from merging extents from the disk with the in-ram
- * representation.  This gets more complex because of the data=ordered code,
- * where the in-ram extents might be locked pending data=ordered completion.
+/**
+ * btrfs_get_extent - Lookup the first extent overlapping a range in a file.
+ * @inode:	file to search in
+ * @page:	page to read extent data into if the extent is inline
+ * @pg_offset:	offset into @page to copy to
+ * @start:	file offset
+ * @len:	length of range starting at @start
+ *
+ * This returns the first &struct extent_map which overlaps with the given
+ * range, reading it from the B-tree and caching it if necessary. Note that
+ * there may be more extents which overlap the given range after the returned
+ * extent_map.
  *
- * This also copies inline extents directly into the page.
+ * If @page is not NULL and the extent is inline, this also reads the extent
+ * data directly into the page and marks the extent up to date in the io_tree.
+ *
+ * Return: ERR_PTR on error, non-NULL extent_map on success.
  */
 struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
-				    struct page *page,
-				    size_t pg_offset, u64 start, u64 len,
-				    int create)
+				    struct page *page, size_t pg_offset,
+				    u64 start, u64 len)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	int ret;
@@ -6979,7 +6320,6 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 	struct extent_map *em = NULL;
 	struct extent_map_tree *em_tree = &inode->extent_tree;
 	struct extent_io_tree *io_tree = &inode->io_tree;
-	const bool new_inline = !page || create;
 
 	read_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, start, len);
@@ -7102,8 +6442,7 @@ next:
 		goto insert;
 	}
 
-	btrfs_extent_item_to_extent_map(inode, path, item,
-			new_inline, em);
+	btrfs_extent_item_to_extent_map(inode, path, item, !page, em);
 
 	if (extent_type == BTRFS_FILE_EXTENT_REG ||
 	    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
@@ -7115,7 +6454,7 @@ next:
 		size_t extent_offset;
 		size_t copy_size;
 
-		if (new_inline)
+		if (!page)
 			goto out;
 
 		size = btrfs_file_extent_ram_bytes(leaf, item);
@@ -7198,7 +6537,7 @@ struct extent_map *btrfs_get_extent_fiemap(struct btrfs_inode *inode,
 	u64 delalloc_end;
 	int err = 0;
 
-	em = btrfs_get_extent(inode, NULL, 0, start, len, 0);
+	em = btrfs_get_extent(inode, NULL, 0, start, len);
 	if (IS_ERR(em))
 		return em;
 	/*
@@ -7823,7 +7162,7 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
 		goto err;
 	}
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len);
 	if (IS_ERR(em)) {
 		ret = PTR_ERR(em);
 		goto unlock_err;
@@ -8375,8 +7714,8 @@ static inline blk_status_t btrfs_lookup_and_bind_dio_csum(struct inode *inode,
 	 * contention.
 	 */
 	if (dip->logical_offset == file_offset) {
-		ret = btrfs_lookup_bio_sums_dio(inode, dip->orig_bio,
-						file_offset);
+		ret = btrfs_lookup_bio_sums(inode, dip->orig_bio, file_offset,
+					    NULL);
 		if (ret)
 			return ret;
 	}
@@ -8889,7 +8228,8 @@ again:
 	ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start,
 					page_end - start + 1);
 	if (ordered) {
-		end = min(page_end, ordered->file_offset + ordered->len - 1);
+		end = min(page_end,
+			  ordered->file_offset + ordered->num_bytes - 1);
 		/*
 		 * IO on this page will never be started, so we need
 		 * to account for any ordered extents now
@@ -9090,7 +8430,6 @@ again:
 		ret = VM_FAULT_SIGBUS;
 		goto out_unlock;
 	}
-	ret2 = 0;
 
 	/* page is wholly or partially inside EOF */
 	if (page_start + PAGE_SIZE > size)
@@ -9114,12 +8453,10 @@ again:
 
 	unlock_extent_cached(io_tree, page_start, page_end, &cached_state);
 
-	if (!ret2) {
-		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
-		sb_end_pagefault(inode->i_sb);
-		extent_changeset_free(data_reserved);
-		return VM_FAULT_LOCKED;
-	}
+	btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
+	sb_end_pagefault(inode->i_sb);
+	extent_changeset_free(data_reserved);
+	return VM_FAULT_LOCKED;
 
 out_unlock:
 	unlock_page(page);
@@ -9417,7 +8754,7 @@ void btrfs_destroy_inode(struct inode *inode)
 		else {
 			btrfs_err(fs_info,
 				  "found ordered extent %llu %llu on inode cleanup",
-				  ordered->file_offset, ordered->len);
+				  ordered->file_offset, ordered->num_bytes);
 			btrfs_remove_ordered_extent(inode, ordered);
 			btrfs_put_ordered_extent(ordered);
 			btrfs_put_ordered_extent(ordered);
@@ -10836,7 +10173,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
 		struct btrfs_block_group *bg;
 		u64 len = isize - start;
 
-		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len, 0);
+		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len);
 		if (IS_ERR(em)) {
 			ret = PTR_ERR(em);
 			goto out;
@@ -11004,11 +10341,6 @@ static const struct inode_operations btrfs_dir_inode_operations = {
 	.update_time	= btrfs_update_time,
 	.tmpfile        = btrfs_tmpfile,
 };
-static const struct inode_operations btrfs_dir_ro_inode_operations = {
-	.lookup		= btrfs_lookup,
-	.permission	= btrfs_permission,
-	.update_time	= btrfs_update_time,
-};
 
 static const struct file_operations btrfs_dir_file_operations = {
 	.llseek		= generic_file_llseek,
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 12ae31e1813e..1b1b6ff855aa 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1128,7 +1128,7 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
 
 		/* get the big lock and read metadata off disk */
 		lock_extent_bits(io_tree, start, end, &cached);
-		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len, 0);
+		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len);
 		unlock_extent_cached(io_tree, start, end, &cached);
 
 		if (IS_ERR(em))
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index fb09bc2f8e4d..ecb9fb6a6fe0 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -20,9 +20,9 @@ static struct kmem_cache *btrfs_ordered_extent_cache;
 
 static u64 entry_end(struct btrfs_ordered_extent *entry)
 {
-	if (entry->file_offset + entry->len < entry->file_offset)
+	if (entry->file_offset + entry->num_bytes < entry->file_offset)
 		return (u64)-1;
-	return entry->file_offset + entry->len;
+	return entry->file_offset + entry->num_bytes;
 }
 
 /* returns NULL if the insertion worked, or it returns the node it did find
@@ -52,14 +52,6 @@ static struct rb_node *tree_insert(struct rb_root *root, u64 file_offset,
 	return NULL;
 }
 
-static void ordered_data_tree_panic(struct inode *inode, int errno,
-					       u64 offset)
-{
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	btrfs_panic(fs_info, errno,
-		    "Inconsistency in ordered tree at offset %llu", offset);
-}
-
 /*
  * look for a given offset in the tree, and if it can't be found return the
  * first lesser offset
@@ -120,7 +112,7 @@ static struct rb_node *__tree_search(struct rb_root *root, u64 file_offset,
 static int offset_in_entry(struct btrfs_ordered_extent *entry, u64 file_offset)
 {
 	if (file_offset < entry->file_offset ||
-	    entry->file_offset + entry->len <= file_offset)
+	    entry->file_offset + entry->num_bytes <= file_offset)
 		return 0;
 	return 1;
 }
@@ -129,7 +121,7 @@ static int range_overlaps(struct btrfs_ordered_extent *entry, u64 file_offset,
 			  u64 len)
 {
 	if (file_offset + len <= entry->file_offset ||
-	    entry->file_offset + entry->len <= file_offset)
+	    entry->file_offset + entry->num_bytes <= file_offset)
 		return 0;
 	return 1;
 }
@@ -161,19 +153,14 @@ static inline struct rb_node *tree_search(struct btrfs_ordered_inode_tree *tree,
 }
 
 /* allocate and add a new ordered_extent into the per-inode tree.
- * file_offset is the logical offset in the file
- *
- * start is the disk block number of an extent already reserved in the
- * extent allocation tree
- *
- * len is the length of the extent
  *
  * The tree is given a single reference on the ordered extent that was
  * inserted.
  */
 static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
-				      u64 start, u64 len, u64 disk_len,
-				      int type, int dio, int compress_type)
+				      u64 disk_bytenr, u64 num_bytes,
+				      u64 disk_num_bytes, int type, int dio,
+				      int compress_type)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
@@ -187,10 +174,10 @@ static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 		return -ENOMEM;
 
 	entry->file_offset = file_offset;
-	entry->start = start;
-	entry->len = len;
-	entry->disk_len = disk_len;
-	entry->bytes_left = len;
+	entry->disk_bytenr = disk_bytenr;
+	entry->num_bytes = num_bytes;
+	entry->disk_num_bytes = disk_num_bytes;
+	entry->bytes_left = num_bytes;
 	entry->inode = igrab(inode);
 	entry->compress_type = compress_type;
 	entry->truncated_len = (u64)-1;
@@ -198,7 +185,7 @@ static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 		set_bit(type, &entry->flags);
 
 	if (dio) {
-		percpu_counter_add_batch(&fs_info->dio_bytes, len,
+		percpu_counter_add_batch(&fs_info->dio_bytes, num_bytes,
 					 fs_info->delalloc_batch);
 		set_bit(BTRFS_ORDERED_DIRECT, &entry->flags);
 	}
@@ -219,7 +206,9 @@ static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 	node = tree_insert(&tree->tree, file_offset,
 			   &entry->rb_node);
 	if (node)
-		ordered_data_tree_panic(inode, -EEXIST, file_offset);
+		btrfs_panic(fs_info, -EEXIST,
+				"inconsistency in ordered tree at offset %llu",
+				file_offset);
 	spin_unlock_irq(&tree->lock);
 
 	spin_lock(&root->ordered_extent_lock);
@@ -247,27 +236,30 @@ static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 }
 
 int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
-			     u64 start, u64 len, u64 disk_len, int type)
+			     u64 disk_bytenr, u64 num_bytes, u64 disk_num_bytes,
+			     int type)
 {
-	return __btrfs_add_ordered_extent(inode, file_offset, start, len,
-					  disk_len, type, 0,
+	return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
+					  num_bytes, disk_num_bytes, type, 0,
 					  BTRFS_COMPRESS_NONE);
 }
 
 int btrfs_add_ordered_extent_dio(struct inode *inode, u64 file_offset,
-				 u64 start, u64 len, u64 disk_len, int type)
+				 u64 disk_bytenr, u64 num_bytes,
+				 u64 disk_num_bytes, int type)
 {
-	return __btrfs_add_ordered_extent(inode, file_offset, start, len,
-					  disk_len, type, 1,
+	return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
+					  num_bytes, disk_num_bytes, type, 1,
 					  BTRFS_COMPRESS_NONE);
 }
 
 int btrfs_add_ordered_extent_compress(struct inode *inode, u64 file_offset,
-				      u64 start, u64 len, u64 disk_len,
-				      int type, int compress_type)
+				      u64 disk_bytenr, u64 num_bytes,
+				      u64 disk_num_bytes, int type,
+				      int compress_type)
 {
-	return __btrfs_add_ordered_extent(inode, file_offset, start, len,
-					  disk_len, type, 0,
+	return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
+					  num_bytes, disk_num_bytes, type, 0,
 					  compress_type);
 }
 
@@ -328,8 +320,8 @@ int btrfs_dec_test_first_ordered_pending(struct inode *inode,
 	}
 
 	dec_start = max(*file_offset, entry->file_offset);
-	dec_end = min(*file_offset + io_size, entry->file_offset +
-		      entry->len);
+	dec_end = min(*file_offset + io_size,
+		      entry->file_offset + entry->num_bytes);
 	*file_offset = dec_end;
 	if (dec_start > dec_end) {
 		btrfs_crit(fs_info, "bad ordering dec_start %llu end %llu",
@@ -471,10 +463,11 @@ void btrfs_remove_ordered_extent(struct inode *inode,
 	btrfs_mod_outstanding_extents(btrfs_inode, -1);
 	spin_unlock(&btrfs_inode->lock);
 	if (root != fs_info->tree_root)
-		btrfs_delalloc_release_metadata(btrfs_inode, entry->len, false);
+		btrfs_delalloc_release_metadata(btrfs_inode, entry->num_bytes,
+						false);
 
 	if (test_bit(BTRFS_ORDERED_DIRECT, &entry->flags))
-		percpu_counter_add_batch(&fs_info->dio_bytes, -entry->len,
+		percpu_counter_add_batch(&fs_info->dio_bytes, -entry->num_bytes,
 					 fs_info->delalloc_batch);
 
 	tree = &btrfs_inode->ordered_tree;
@@ -534,8 +527,8 @@ u64 btrfs_wait_ordered_extents(struct btrfs_root *root, u64 nr,
 		ordered = list_first_entry(&splice, struct btrfs_ordered_extent,
 					   root_extent_list);
 
-		if (range_end <= ordered->start ||
-		    ordered->start + ordered->disk_len <= range_start) {
+		if (range_end <= ordered->disk_bytenr ||
+		    ordered->disk_bytenr + ordered->disk_num_bytes <= range_start) {
 			list_move_tail(&ordered->root_extent_list, &skipped);
 			cond_resched_lock(&root->ordered_extent_lock);
 			continue;
@@ -619,7 +612,7 @@ void btrfs_start_ordered_extent(struct inode *inode,
 				       int wait)
 {
 	u64 start = entry->file_offset;
-	u64 end = start + entry->len - 1;
+	u64 end = start + entry->num_bytes - 1;
 
 	trace_btrfs_ordered_extent_start(inode, entry);
 
@@ -680,7 +673,7 @@ int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
 			btrfs_put_ordered_extent(ordered);
 			break;
 		}
-		if (ordered->file_offset + ordered->len <= start) {
+		if (ordered->file_offset + ordered->num_bytes <= start) {
 			btrfs_put_ordered_extent(ordered);
 			break;
 		}
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index 4eb0319a86d7..3beb4da4ab41 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -67,14 +67,13 @@ struct btrfs_ordered_extent {
 	/* logical offset in the file */
 	u64 file_offset;
 
-	/* disk byte number */
-	u64 start;
-
-	/* ram length of the extent in bytes */
-	u64 len;
-
-	/* extent length on disk */
-	u64 disk_len;
+	/*
+	 * These fields directly correspond to the same fields in
+	 * btrfs_file_extent_item.
+	 */
+	u64 disk_bytenr;
+	u64 num_bytes;
+	u64 disk_num_bytes;
 
 	/* number of bytes that still need writing */
 	u64 bytes_left;
@@ -161,12 +160,15 @@ int btrfs_dec_test_first_ordered_pending(struct inode *inode,
 				   u64 *file_offset, u64 io_size,
 				   int uptodate);
 int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
-			     u64 start, u64 len, u64 disk_len, int type);
+			     u64 disk_bytenr, u64 num_bytes, u64 disk_num_bytes,
+			     int type);
 int btrfs_add_ordered_extent_dio(struct inode *inode, u64 file_offset,
-				 u64 start, u64 len, u64 disk_len, int type);
+				 u64 disk_bytenr, u64 num_bytes,
+				 u64 disk_num_bytes, int type);
 int btrfs_add_ordered_extent_compress(struct inode *inode, u64 file_offset,
-				      u64 start, u64 len, u64 disk_len,
-				      int type, int compress_type);
+				      u64 disk_bytenr, u64 num_bytes,
+				      u64 disk_num_bytes, int type,
+				      int compress_type);
 void btrfs_add_ordered_sum(struct btrfs_ordered_extent *entry,
 			   struct btrfs_ordered_sum *sum);
 struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct inode *inode,
diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
index 873b6b694107..61f44e78e3c9 100644
--- a/fs/btrfs/print-tree.c
+++ b/fs/btrfs/print-tree.c
@@ -317,7 +317,7 @@ void btrfs_print_leaf(struct extent_buffer *l)
 			print_uuid_item(l, btrfs_item_ptr_offset(l, i),
 					btrfs_item_size_nr(l, i));
 			break;
-		};
+		}
 	}
 }
 
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 39fc8c3d3a75..98d9a50352d6 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1243,7 +1243,6 @@ int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
 			      u64 dst)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_root *quota_root;
 	struct btrfs_qgroup *parent;
 	struct btrfs_qgroup *member;
 	struct btrfs_qgroup_list *list;
@@ -1259,9 +1258,8 @@ int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
 		return -ENOMEM;
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
-	quota_root = fs_info->quota_root;
-	if (!quota_root) {
-		ret = -EINVAL;
+	if (!fs_info->quota_root) {
+		ret = -ENOTCONN;
 		goto out;
 	}
 	member = find_qgroup_rb(fs_info, src);
@@ -1307,7 +1305,6 @@ static int __del_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
 				 u64 dst)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_root *quota_root;
 	struct btrfs_qgroup *parent;
 	struct btrfs_qgroup *member;
 	struct btrfs_qgroup_list *list;
@@ -1320,9 +1317,8 @@ static int __del_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
 	if (!tmp)
 		return -ENOMEM;
 
-	quota_root = fs_info->quota_root;
-	if (!quota_root) {
-		ret = -EINVAL;
+	if (!fs_info->quota_root) {
+		ret = -ENOTCONN;
 		goto out;
 	}
 
@@ -1387,11 +1383,11 @@ int btrfs_create_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid)
 	int ret = 0;
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
-	quota_root = fs_info->quota_root;
-	if (!quota_root) {
-		ret = -EINVAL;
+	if (!fs_info->quota_root) {
+		ret = -ENOTCONN;
 		goto out;
 	}
+	quota_root = fs_info->quota_root;
 	qgroup = find_qgroup_rb(fs_info, qgroupid);
 	if (qgroup) {
 		ret = -EEXIST;
@@ -1416,15 +1412,13 @@ out:
 int btrfs_remove_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_root *quota_root;
 	struct btrfs_qgroup *qgroup;
 	struct btrfs_qgroup_list *list;
 	int ret = 0;
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
-	quota_root = fs_info->quota_root;
-	if (!quota_root) {
-		ret = -EINVAL;
+	if (!fs_info->quota_root) {
+		ret = -ENOTCONN;
 		goto out;
 	}
 
@@ -1465,7 +1459,6 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid,
 		       struct btrfs_qgroup_limit *limit)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_root *quota_root;
 	struct btrfs_qgroup *qgroup;
 	int ret = 0;
 	/* Sometimes we would want to clear the limit on this qgroup.
@@ -1475,9 +1468,8 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid,
 	const u64 CLEAR_VALUE = -1;
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
-	quota_root = fs_info->quota_root;
-	if (!quota_root) {
-		ret = -EINVAL;
+	if (!fs_info->quota_root) {
+		ret = -ENOTCONN;
 		goto out;
 	}
 
@@ -2582,10 +2574,9 @@ cleanup:
 int btrfs_run_qgroups(struct btrfs_trans_handle *trans)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_root *quota_root = fs_info->quota_root;
 	int ret = 0;
 
-	if (!quota_root)
+	if (!fs_info->quota_root)
 		return ret;
 
 	spin_lock(&fs_info->qgroup_lock);
@@ -2879,7 +2870,6 @@ static bool qgroup_check_limits(struct btrfs_fs_info *fs_info,
 static int qgroup_reserve(struct btrfs_root *root, u64 num_bytes, bool enforce,
 			  enum btrfs_qgroup_rsv_type type)
 {
-	struct btrfs_root *quota_root;
 	struct btrfs_qgroup *qgroup;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	u64 ref_root = root->root_key.objectid;
@@ -2898,8 +2888,7 @@ static int qgroup_reserve(struct btrfs_root *root, u64 num_bytes, bool enforce,
 		enforce = false;
 
 	spin_lock(&fs_info->qgroup_lock);
-	quota_root = fs_info->quota_root;
-	if (!quota_root)
+	if (!fs_info->quota_root)
 		goto out;
 
 	qgroup = find_qgroup_rb(fs_info, ref_root);
@@ -2966,7 +2955,6 @@ void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,
 			       u64 ref_root, u64 num_bytes,
 			       enum btrfs_qgroup_rsv_type type)
 {
-	struct btrfs_root *quota_root;
 	struct btrfs_qgroup *qgroup;
 	struct ulist_node *unode;
 	struct ulist_iterator uiter;
@@ -2984,8 +2972,7 @@ void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,
 	}
 	spin_lock(&fs_info->qgroup_lock);
 
-	quota_root = fs_info->quota_root;
-	if (!quota_root)
+	if (!fs_info->quota_root)
 		goto out;
 
 	qgroup = find_qgroup_rb(fs_info, ref_root);
@@ -3685,7 +3672,6 @@ void __btrfs_qgroup_free_meta(struct btrfs_root *root, int num_bytes,
 static void qgroup_convert_meta(struct btrfs_fs_info *fs_info, u64 ref_root,
 				int num_bytes)
 {
-	struct btrfs_root *quota_root = fs_info->quota_root;
 	struct btrfs_qgroup *qgroup;
 	struct ulist_node *unode;
 	struct ulist_iterator uiter;
@@ -3693,7 +3679,7 @@ static void qgroup_convert_meta(struct btrfs_fs_info *fs_info, u64 ref_root,
 
 	if (num_bytes == 0)
 		return;
-	if (!quota_root)
+	if (!fs_info->quota_root)
 		return;
 
 	spin_lock(&fs_info->qgroup_lock);
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index da5abd62db22..995d4b8b1cfd 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4332,6 +4332,15 @@ static void describe_relocation(struct btrfs_fs_info *fs_info,
 		   block_group->start, buf);
 }
 
+static const char *stage_to_string(int stage)
+{
+	if (stage == MOVE_DATA_EXTENTS)
+		return "move data extents";
+	if (stage == UPDATE_DATA_PTRS)
+		return "update data pointers";
+	return "unknown";
+}
+
 /*
  * function to relocate all extents in a block group.
  */
@@ -4406,12 +4415,15 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
 				 rc->block_group->length);
 
 	while (1) {
+		int finishes_stage;
+
 		mutex_lock(&fs_info->cleaner_mutex);
 		ret = relocate_block_group(rc);
 		mutex_unlock(&fs_info->cleaner_mutex);
 		if (ret < 0)
 			err = ret;
 
+		finishes_stage = rc->stage;
 		/*
 		 * We may have gotten ENOSPC after we already dirtied some
 		 * extents.  If writeout happens while we're relocating a
@@ -4437,8 +4449,8 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
 		if (rc->extents_found == 0)
 			break;
 
-		btrfs_info(fs_info, "found %llu extents", rc->extents_found);
-
+		btrfs_info(fs_info, "found %llu extents, stage: %s",
+			   rc->extents_found, stage_to_string(finishes_stage));
 	}
 
 	WARN_ON(rc->block_group->pinned > 0);
@@ -4656,7 +4668,7 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
 	LIST_HEAD(list);
 
 	ordered = btrfs_lookup_ordered_extent(inode, file_pos);
-	BUG_ON(ordered->file_offset != file_pos || ordered->len != len);
+	BUG_ON(ordered->file_offset != file_pos || ordered->num_bytes != len);
 
 	disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
 	ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
@@ -4680,7 +4692,7 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
 		 * disk_len vs real len like with real inodes since it's all
 		 * disk length.
 		 */
-		new_bytenr = ordered->start + (sums->bytenr - disk_bytenr);
+		new_bytenr = ordered->disk_bytenr + sums->bytenr - disk_bytenr;
 		sums->bytenr = new_bytenr;
 
 		btrfs_add_ordered_sum(ordered, sums);
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index fd266a2d15ec..61b37c56a7fb 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -8,6 +8,7 @@
 #include <linux/sched/mm.h>
 #include <crypto/hash.h>
 #include "ctree.h"
+#include "discard.h"
 #include "volumes.h"
 #include "disk-io.h"
 #include "ordered-data.h"
@@ -3682,7 +3683,11 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
 		if (!cache->removed && !cache->ro && cache->reserved == 0 &&
 		    cache->used == 0) {
 			spin_unlock(&cache->lock);
-			btrfs_mark_bg_unused(cache);
+			if (btrfs_test_opt(fs_info, DISCARD_ASYNC))
+				btrfs_discard_queue_work(&fs_info->discard_ctl,
+							 cache);
+			else
+				btrfs_mark_bg_unused(cache);
 		} else {
 			spin_unlock(&cache->lock);
 		}
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index f09aa6ee9113..537bc310a673 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -161,8 +161,7 @@ static inline u64 calc_global_rsv_need_space(struct btrfs_block_rsv *global)
 
 static int can_overcommit(struct btrfs_fs_info *fs_info,
 			  struct btrfs_space_info *space_info, u64 bytes,
-			  enum btrfs_reserve_flush_enum flush,
-			  bool system_chunk)
+			  enum btrfs_reserve_flush_enum flush)
 {
 	u64 profile;
 	u64 avail;
@@ -173,7 +172,7 @@ static int can_overcommit(struct btrfs_fs_info *fs_info,
 	if (space_info->flags & BTRFS_BLOCK_GROUP_DATA)
 		return 0;
 
-	if (system_chunk)
+	if (space_info->flags & BTRFS_BLOCK_GROUP_SYSTEM)
 		profile = btrfs_system_alloc_profile(fs_info);
 	else
 		profile = btrfs_metadata_alloc_profile(fs_info);
@@ -227,8 +226,7 @@ again:
 
 		/* Check and see if our ticket can be satisified now. */
 		if ((used + ticket->bytes <= space_info->total_bytes) ||
-		    can_overcommit(fs_info, space_info, ticket->bytes, flush,
-				   false)) {
+		    can_overcommit(fs_info, space_info, ticket->bytes, flush)) {
 			btrfs_space_info_update_bytes_may_use(fs_info,
 							      space_info,
 							      ticket->bytes);
@@ -626,8 +624,7 @@ static void flush_space(struct btrfs_fs_info *fs_info,
 
 static inline u64
 btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
-				 struct btrfs_space_info *space_info,
-				 bool system_chunk)
+				 struct btrfs_space_info *space_info)
 {
 	struct reserve_ticket *ticket;
 	u64 used;
@@ -643,13 +640,12 @@ btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
 
 	to_reclaim = min_t(u64, num_online_cpus() * SZ_1M, SZ_16M);
 	if (can_overcommit(fs_info, space_info, to_reclaim,
-			   BTRFS_RESERVE_FLUSH_ALL, system_chunk))
+			   BTRFS_RESERVE_FLUSH_ALL))
 		return 0;
 
 	used = btrfs_space_info_used(space_info, true);
 
-	if (can_overcommit(fs_info, space_info, SZ_1M,
-			   BTRFS_RESERVE_FLUSH_ALL, system_chunk))
+	if (can_overcommit(fs_info, space_info, SZ_1M, BTRFS_RESERVE_FLUSH_ALL))
 		expected = div_factor_fine(space_info->total_bytes, 95);
 	else
 		expected = div_factor_fine(space_info->total_bytes, 90);
@@ -665,7 +661,7 @@ btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
 
 static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
 					struct btrfs_space_info *space_info,
-					u64 used, bool system_chunk)
+					u64 used)
 {
 	u64 thresh = div_factor_fine(space_info->total_bytes, 98);
 
@@ -673,8 +669,7 @@ static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
 	if ((space_info->bytes_used + space_info->bytes_reserved) >= thresh)
 		return 0;
 
-	if (!btrfs_calc_reclaim_metadata_size(fs_info, space_info,
-					      system_chunk))
+	if (!btrfs_calc_reclaim_metadata_size(fs_info, space_info))
 		return 0;
 
 	return (used >= thresh && !btrfs_fs_closing(fs_info) &&
@@ -765,8 +760,7 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 	space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
 
 	spin_lock(&space_info->lock);
-	to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info,
-						      false);
+	to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
 	if (!to_reclaim) {
 		space_info->flush = 0;
 		spin_unlock(&space_info->lock);
@@ -785,8 +779,7 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 			return;
 		}
 		to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info,
-							      space_info,
-							      false);
+							      space_info);
 		if (last_tickets_id == space_info->tickets_id) {
 			flush_state++;
 		} else {
@@ -858,8 +851,7 @@ static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
 	int flush_state;
 
 	spin_lock(&space_info->lock);
-	to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info,
-						      false);
+	to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
 	if (!to_reclaim) {
 		spin_unlock(&space_info->lock);
 		return;
@@ -990,8 +982,7 @@ static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
 static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
 				    struct btrfs_space_info *space_info,
 				    u64 orig_bytes,
-				    enum btrfs_reserve_flush_enum flush,
-				    bool system_chunk)
+				    enum btrfs_reserve_flush_enum flush)
 {
 	struct reserve_ticket ticket;
 	u64 used;
@@ -1013,8 +1004,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
 	 */
 	if (!pending_tickets &&
 	    ((used + orig_bytes <= space_info->total_bytes) ||
-	     can_overcommit(fs_info, space_info, orig_bytes, flush,
-			   system_chunk))) {
+	     can_overcommit(fs_info, space_info, orig_bytes, flush))) {
 		btrfs_space_info_update_bytes_may_use(fs_info, space_info,
 						      orig_bytes);
 		ret = 0;
@@ -1054,8 +1044,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
 		 * the async reclaim as we will panic.
 		 */
 		if (!test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags) &&
-		    need_do_async_reclaim(fs_info, space_info,
-					  used, system_chunk) &&
+		    need_do_async_reclaim(fs_info, space_info, used) &&
 		    !work_busy(&fs_info->async_reclaim_work)) {
 			trace_btrfs_trigger_flush(fs_info, space_info->flags,
 						  orig_bytes, flush, "preempt");
@@ -1092,10 +1081,9 @@ int btrfs_reserve_metadata_bytes(struct btrfs_root *root,
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
 	int ret;
-	bool system_chunk = (root == fs_info->chunk_root);
 
 	ret = __reserve_metadata_bytes(fs_info, block_rsv->space_info,
-				       orig_bytes, flush, system_chunk);
+				       orig_bytes, flush);
 	if (ret == -ENOSPC &&
 	    unlikely(root->orphan_cleanup_state == ORPHAN_CLEANUP_STARTED)) {
 		if (block_rsv != global_rsv &&
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f452a94abdc3..a906315efd19 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -46,6 +46,7 @@
 #include "sysfs.h"
 #include "tests/btrfs-tests.h"
 #include "block-group.h"
+#include "discard.h"
 
 #include "qgroup.h"
 #define CREATE_TRACE_POINTS
@@ -146,6 +147,8 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
 	if (sb_rdonly(sb))
 		return;
 
+	btrfs_discard_stop(fs_info);
+
 	/* btrfs handle error by forcing the filesystem readonly */
 	sb->s_flags |= SB_RDONLY;
 	btrfs_info(fs_info, "forced readonly");
@@ -313,6 +316,7 @@ enum {
 	Opt_datasum, Opt_nodatasum,
 	Opt_defrag, Opt_nodefrag,
 	Opt_discard, Opt_nodiscard,
+	Opt_discard_mode,
 	Opt_nologreplay,
 	Opt_norecovery,
 	Opt_ratio,
@@ -375,6 +379,7 @@ static const match_table_t tokens = {
 	{Opt_defrag, "autodefrag"},
 	{Opt_nodefrag, "noautodefrag"},
 	{Opt_discard, "discard"},
+	{Opt_discard_mode, "discard=%s"},
 	{Opt_nodiscard, "nodiscard"},
 	{Opt_nologreplay, "nologreplay"},
 	{Opt_norecovery, "norecovery"},
@@ -695,12 +700,26 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 				   info->metadata_ratio);
 			break;
 		case Opt_discard:
-			btrfs_set_and_info(info, DISCARD,
-					   "turning on discard");
+		case Opt_discard_mode:
+			if (token == Opt_discard ||
+			    strcmp(args[0].from, "sync") == 0) {
+				btrfs_clear_opt(info->mount_opt, DISCARD_ASYNC);
+				btrfs_set_and_info(info, DISCARD_SYNC,
+						   "turning on sync discard");
+			} else if (strcmp(args[0].from, "async") == 0) {
+				btrfs_clear_opt(info->mount_opt, DISCARD_SYNC);
+				btrfs_set_and_info(info, DISCARD_ASYNC,
+						   "turning on async discard");
+			} else {
+				ret = -EINVAL;
+				goto out;
+			}
 			break;
 		case Opt_nodiscard:
-			btrfs_clear_and_info(info, DISCARD,
+			btrfs_clear_and_info(info, DISCARD_SYNC,
 					     "turning off discard");
+			btrfs_clear_and_info(info, DISCARD_ASYNC,
+					     "turning off async discard");
 			break;
 		case Opt_space_cache:
 		case Opt_space_cache_version:
@@ -1322,8 +1341,10 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",nologreplay");
 	if (btrfs_test_opt(info, FLUSHONCOMMIT))
 		seq_puts(seq, ",flushoncommit");
-	if (btrfs_test_opt(info, DISCARD))
+	if (btrfs_test_opt(info, DISCARD_SYNC))
 		seq_puts(seq, ",discard");
+	if (btrfs_test_opt(info, DISCARD_ASYNC))
+		seq_puts(seq, ",discard=async");
 	if (!(info->sb->s_flags & SB_POSIXACL))
 		seq_puts(seq, ",noacl");
 	if (btrfs_test_opt(info, SPACE_CACHE))
@@ -1713,6 +1734,14 @@ static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info,
 		btrfs_cleanup_defrag_inodes(fs_info);
 	}
 
+	/* If we toggled discard async */
+	if (!btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
+	    btrfs_test_opt(fs_info, DISCARD_ASYNC))
+		btrfs_discard_resume(fs_info);
+	else if (btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
+		 !btrfs_test_opt(fs_info, DISCARD_ASYNC))
+		btrfs_discard_cleanup(fs_info);
+
 	clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);
 }
 
@@ -1760,6 +1789,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 		 */
 		cancel_work_sync(&fs_info->async_reclaim_work);
 
+		btrfs_discard_cleanup(fs_info);
+
 		/* wait for the uuid_scan task to finish */
 		down(&fs_info->uuid_tree_rescan_sem);
 		/* avoid complains from lockdep et al. */
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 5ebbe8a5ee76..7436422194da 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -12,6 +12,7 @@
 #include <crypto/hash.h>
 
 #include "ctree.h"
+#include "discard.h"
 #include "disk-io.h"
 #include "transaction.h"
 #include "sysfs.h"
@@ -339,11 +340,177 @@ static const struct attribute_group btrfs_static_feature_attr_group = {
 #ifdef CONFIG_BTRFS_DEBUG
 
 /*
+ * Discard statistics and tunables
+ */
+#define discard_to_fs_info(_kobj)	to_fs_info((_kobj)->parent->parent)
+
+static ssize_t btrfs_discardable_bytes_show(struct kobject *kobj,
+					    struct kobj_attribute *a,
+					    char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+			atomic64_read(&fs_info->discard_ctl.discardable_bytes));
+}
+BTRFS_ATTR(discard, discardable_bytes, btrfs_discardable_bytes_show);
+
+static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n",
+			atomic_read(&fs_info->discard_ctl.discardable_extents));
+}
+BTRFS_ATTR(discard, discardable_extents, btrfs_discardable_extents_show);
+
+static ssize_t btrfs_discard_bitmap_bytes_show(struct kobject *kobj,
+					       struct kobj_attribute *a,
+					       char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+			fs_info->discard_ctl.discard_bitmap_bytes);
+}
+BTRFS_ATTR(discard, discard_bitmap_bytes, btrfs_discard_bitmap_bytes_show);
+
+static ssize_t btrfs_discard_bytes_saved_show(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+		atomic64_read(&fs_info->discard_ctl.discard_bytes_saved));
+}
+BTRFS_ATTR(discard, discard_bytes_saved, btrfs_discard_bytes_saved_show);
+
+static ssize_t btrfs_discard_extent_bytes_show(struct kobject *kobj,
+					       struct kobj_attribute *a,
+					       char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+			fs_info->discard_ctl.discard_extent_bytes);
+}
+BTRFS_ATTR(discard, discard_extent_bytes, btrfs_discard_extent_bytes_show);
+
+static ssize_t btrfs_discard_iops_limit_show(struct kobject *kobj,
+					     struct kobj_attribute *a,
+					     char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+			READ_ONCE(fs_info->discard_ctl.iops_limit));
+}
+
+static ssize_t btrfs_discard_iops_limit_store(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	u32 iops_limit;
+	int ret;
+
+	ret = kstrtou32(buf, 10, &iops_limit);
+	if (ret)
+		return -EINVAL;
+
+	WRITE_ONCE(discard_ctl->iops_limit, iops_limit);
+
+	return len;
+}
+BTRFS_ATTR_RW(discard, iops_limit, btrfs_discard_iops_limit_show,
+	      btrfs_discard_iops_limit_store);
+
+static ssize_t btrfs_discard_kbps_limit_show(struct kobject *kobj,
+					     struct kobj_attribute *a,
+					     char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+			READ_ONCE(fs_info->discard_ctl.kbps_limit));
+}
+
+static ssize_t btrfs_discard_kbps_limit_store(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	u32 kbps_limit;
+	int ret;
+
+	ret = kstrtou32(buf, 10, &kbps_limit);
+	if (ret)
+		return -EINVAL;
+
+	WRITE_ONCE(discard_ctl->kbps_limit, kbps_limit);
+
+	return len;
+}
+BTRFS_ATTR_RW(discard, kbps_limit, btrfs_discard_kbps_limit_show,
+	      btrfs_discard_kbps_limit_store);
+
+static ssize_t btrfs_discard_max_discard_size_show(struct kobject *kobj,
+						   struct kobj_attribute *a,
+						   char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%llu\n",
+			READ_ONCE(fs_info->discard_ctl.max_discard_size));
+}
+
+static ssize_t btrfs_discard_max_discard_size_store(struct kobject *kobj,
+						    struct kobj_attribute *a,
+						    const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	u64 max_discard_size;
+	int ret;
+
+	ret = kstrtou64(buf, 10, &max_discard_size);
+	if (ret)
+		return -EINVAL;
+
+	WRITE_ONCE(discard_ctl->max_discard_size, max_discard_size);
+
+	return len;
+}
+BTRFS_ATTR_RW(discard, max_discard_size, btrfs_discard_max_discard_size_show,
+	      btrfs_discard_max_discard_size_store);
+
+static const struct attribute *discard_debug_attrs[] = {
+	BTRFS_ATTR_PTR(discard, discardable_bytes),
+	BTRFS_ATTR_PTR(discard, discardable_extents),
+	BTRFS_ATTR_PTR(discard, discard_bitmap_bytes),
+	BTRFS_ATTR_PTR(discard, discard_bytes_saved),
+	BTRFS_ATTR_PTR(discard, discard_extent_bytes),
+	BTRFS_ATTR_PTR(discard, iops_limit),
+	BTRFS_ATTR_PTR(discard, kbps_limit),
+	BTRFS_ATTR_PTR(discard, max_discard_size),
+	NULL,
+};
+
+/*
  * Runtime debugging exported via sysfs
  *
  * /sys/fs/btrfs/debug - applies to module or all filesystems
  * /sys/fs/btrfs/UUID  - applies only to the given filesystem
  */
+static const struct attribute *btrfs_debug_mount_attrs[] = {
+	NULL,
+};
+
 static struct attribute *btrfs_debug_feature_attrs[] = {
 	NULL
 };
@@ -734,10 +901,10 @@ static int addrm_unknown_feature_attrs(struct btrfs_fs_info *fs_info, bool add)
 
 static void __btrfs_sysfs_remove_fsid(struct btrfs_fs_devices *fs_devs)
 {
-	if (fs_devs->device_dir_kobj) {
-		kobject_del(fs_devs->device_dir_kobj);
-		kobject_put(fs_devs->device_dir_kobj);
-		fs_devs->device_dir_kobj = NULL;
+	if (fs_devs->devices_kobj) {
+		kobject_del(fs_devs->devices_kobj);
+		kobject_put(fs_devs->devices_kobj);
+		fs_devs->devices_kobj = NULL;
 	}
 
 	if (fs_devs->fsid_kobj.state_initialized) {
@@ -771,6 +938,19 @@ void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info)
 		kobject_del(fs_info->space_info_kobj);
 		kobject_put(fs_info->space_info_kobj);
 	}
+#ifdef CONFIG_BTRFS_DEBUG
+	if (fs_info->discard_debug_kobj) {
+		sysfs_remove_files(fs_info->discard_debug_kobj,
+				   discard_debug_attrs);
+		kobject_del(fs_info->discard_debug_kobj);
+		kobject_put(fs_info->discard_debug_kobj);
+	}
+	if (fs_info->debug_kobj) {
+		sysfs_remove_files(fs_info->debug_kobj, btrfs_debug_mount_attrs);
+		kobject_del(fs_info->debug_kobj);
+		kobject_put(fs_info->debug_kobj);
+	}
+#endif
 	addrm_unknown_feature_attrs(fs_info, false);
 	sysfs_remove_group(&fs_info->fs_devices->fsid_kobj, &btrfs_feature_attr_group);
 	sysfs_remove_files(&fs_info->fs_devices->fsid_kobj, btrfs_attrs);
@@ -969,46 +1149,120 @@ int btrfs_sysfs_rm_device_link(struct btrfs_fs_devices *fs_devices,
 	struct hd_struct *disk;
 	struct kobject *disk_kobj;
 
-	if (!fs_devices->device_dir_kobj)
+	if (!fs_devices->devices_kobj)
 		return -EINVAL;
 
-	if (one_device && one_device->bdev) {
-		disk = one_device->bdev->bd_part;
-		disk_kobj = &part_to_dev(disk)->kobj;
+	if (one_device) {
+		if (one_device->bdev) {
+			disk = one_device->bdev->bd_part;
+			disk_kobj = &part_to_dev(disk)->kobj;
+			sysfs_remove_link(fs_devices->devices_kobj,
+					  disk_kobj->name);
+		}
 
-		sysfs_remove_link(fs_devices->device_dir_kobj,
-						disk_kobj->name);
-	}
+		kobject_del(&one_device->devid_kobj);
+		kobject_put(&one_device->devid_kobj);
+
+		wait_for_completion(&one_device->kobj_unregister);
 
-	if (one_device)
 		return 0;
+	}
 
-	list_for_each_entry(one_device,
-			&fs_devices->devices, dev_list) {
-		if (!one_device->bdev)
-			continue;
-		disk = one_device->bdev->bd_part;
-		disk_kobj = &part_to_dev(disk)->kobj;
+	list_for_each_entry(one_device, &fs_devices->devices, dev_list) {
+
+		if (one_device->bdev) {
+			disk = one_device->bdev->bd_part;
+			disk_kobj = &part_to_dev(disk)->kobj;
+			sysfs_remove_link(fs_devices->devices_kobj,
+					  disk_kobj->name);
+		}
+		kobject_del(&one_device->devid_kobj);
+		kobject_put(&one_device->devid_kobj);
 
-		sysfs_remove_link(fs_devices->device_dir_kobj,
-						disk_kobj->name);
+		wait_for_completion(&one_device->kobj_unregister);
 	}
 
 	return 0;
 }
 
-int btrfs_sysfs_add_device(struct btrfs_fs_devices *fs_devs)
+static ssize_t btrfs_devinfo_in_fs_metadata_show(struct kobject *kobj,
+					         struct kobj_attribute *a,
+					         char *buf)
 {
-	if (!fs_devs->device_dir_kobj)
-		fs_devs->device_dir_kobj = kobject_create_and_add("devices",
-						&fs_devs->fsid_kobj);
+	int val;
+	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
+						   devid_kobj);
 
-	if (!fs_devs->device_dir_kobj)
-		return -ENOMEM;
+	val = !!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 
-	return 0;
+	return snprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+BTRFS_ATTR(devid, in_fs_metadata, btrfs_devinfo_in_fs_metadata_show);
+
+static ssize_t btrfs_sysfs_missing_show(struct kobject *kobj,
+					struct kobj_attribute *a, char *buf)
+{
+	int val;
+	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
+						   devid_kobj);
+
+	val = !!test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+BTRFS_ATTR(devid, missing, btrfs_sysfs_missing_show);
+
+static ssize_t btrfs_devinfo_replace_target_show(struct kobject *kobj,
+					         struct kobj_attribute *a,
+					         char *buf)
+{
+	int val;
+	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
+						   devid_kobj);
+
+	val = !!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+BTRFS_ATTR(devid, replace_target, btrfs_devinfo_replace_target_show);
+
+static ssize_t btrfs_devinfo_writeable_show(struct kobject *kobj,
+					    struct kobj_attribute *a, char *buf)
+{
+	int val;
+	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
+						   devid_kobj);
+
+	val = !!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+BTRFS_ATTR(devid, writeable, btrfs_devinfo_writeable_show);
+
+static struct attribute *devid_attrs[] = {
+	BTRFS_ATTR_PTR(devid, in_fs_metadata),
+	BTRFS_ATTR_PTR(devid, missing),
+	BTRFS_ATTR_PTR(devid, replace_target),
+	BTRFS_ATTR_PTR(devid, writeable),
+	NULL
+};
+ATTRIBUTE_GROUPS(devid);
+
+static void btrfs_release_devid_kobj(struct kobject *kobj)
+{
+	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
+						   devid_kobj);
+
+	memset(&device->devid_kobj, 0, sizeof(struct kobject));
+	complete(&device->kobj_unregister);
 }
 
+static struct kobj_type devid_ktype = {
+	.sysfs_ops	= &kobj_sysfs_ops,
+	.default_groups = devid_groups,
+	.release	= btrfs_release_devid_kobj,
+};
+
 int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices,
 				struct btrfs_device *one_device)
 {
@@ -1016,22 +1270,31 @@ int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices,
 	struct btrfs_device *dev;
 
 	list_for_each_entry(dev, &fs_devices->devices, dev_list) {
-		struct hd_struct *disk;
-		struct kobject *disk_kobj;
-
-		if (!dev->bdev)
-			continue;
 
 		if (one_device && one_device != dev)
 			continue;
 
-		disk = dev->bdev->bd_part;
-		disk_kobj = &part_to_dev(disk)->kobj;
+		if (dev->bdev) {
+			struct hd_struct *disk;
+			struct kobject *disk_kobj;
+
+			disk = dev->bdev->bd_part;
+			disk_kobj = &part_to_dev(disk)->kobj;
 
-		error = sysfs_create_link(fs_devices->device_dir_kobj,
-					  disk_kobj, disk_kobj->name);
-		if (error)
+			error = sysfs_create_link(fs_devices->devices_kobj,
+						  disk_kobj, disk_kobj->name);
+			if (error)
+				break;
+		}
+
+		init_completion(&dev->kobj_unregister);
+		error = kobject_init_and_add(&dev->devid_kobj, &devid_ktype,
+					     fs_devices->devices_kobj, "%llu",
+					     dev->devid);
+		if (error) {
+			kobject_put(&dev->devid_kobj);
 			break;
+		}
 	}
 
 	return error;
@@ -1063,27 +1326,49 @@ void btrfs_sysfs_update_sprout_fsid(struct btrfs_fs_devices *fs_devices,
 				"sysfs: failed to create fsid for sprout");
 }
 
+void btrfs_sysfs_update_devid(struct btrfs_device *device)
+{
+	char tmp[24];
+
+	snprintf(tmp, sizeof(tmp), "%llu", device->devid);
+
+	if (kobject_rename(&device->devid_kobj, tmp))
+		btrfs_warn(device->fs_devices->fs_info,
+			   "sysfs: failed to update devid for %llu",
+			   device->devid);
+}
+
 /* /sys/fs/btrfs/ entry */
 static struct kset *btrfs_kset;
 
 /*
+ * Creates:
+ *		/sys/fs/btrfs/UUID
+ *
  * Can be called by the device discovery thread.
- * And parent can be specified for seed device
  */
-int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs,
-				struct kobject *parent)
+int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs)
 {
 	int error;
 
 	init_completion(&fs_devs->kobj_unregister);
 	fs_devs->fsid_kobj.kset = btrfs_kset;
-	error = kobject_init_and_add(&fs_devs->fsid_kobj,
-				&btrfs_ktype, parent, "%pU", fs_devs->fsid);
+	error = kobject_init_and_add(&fs_devs->fsid_kobj, &btrfs_ktype, NULL,
+				     "%pU", fs_devs->fsid);
 	if (error) {
 		kobject_put(&fs_devs->fsid_kobj);
 		return error;
 	}
 
+	fs_devs->devices_kobj = kobject_create_and_add("devices",
+						       &fs_devs->fsid_kobj);
+	if (!fs_devs->devices_kobj) {
+		btrfs_err(fs_devs->fs_info,
+			  "failed to init sysfs device interface");
+		kobject_put(&fs_devs->fsid_kobj);
+		return -ENOMEM;
+	}
+
 	return 0;
 }
 
@@ -1111,8 +1396,26 @@ int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
 		goto failure;
 
 #ifdef CONFIG_BTRFS_DEBUG
-	error = sysfs_create_group(fsid_kobj,
-				   &btrfs_debug_feature_attr_group);
+	fs_info->debug_kobj = kobject_create_and_add("debug", fsid_kobj);
+	if (!fs_info->debug_kobj) {
+		error = -ENOMEM;
+		goto failure;
+	}
+
+	error = sysfs_create_files(fs_info->debug_kobj, btrfs_debug_mount_attrs);
+	if (error)
+		goto failure;
+
+	/* Discard directory */
+	fs_info->discard_debug_kobj = kobject_create_and_add("discard",
+						     fs_info->debug_kobj);
+	if (!fs_info->discard_debug_kobj) {
+		error = -ENOMEM;
+		goto failure;
+	}
+
+	error = sysfs_create_files(fs_info->discard_debug_kobj,
+				   discard_debug_attrs);
 	if (error)
 		goto failure;
 #endif
@@ -1209,6 +1512,9 @@ void __cold btrfs_exit_sysfs(void)
 	sysfs_unmerge_group(&btrfs_kset->kobj,
 			    &btrfs_static_feature_attr_group);
 	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);
+#ifdef CONFIG_BTRFS_DEBUG
+	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_debug_feature_attr_group);
+#endif
 	kset_unregister(btrfs_kset);
 }
 
diff --git a/fs/btrfs/sysfs.h b/fs/btrfs/sysfs.h
index e10c3adfc30f..c68582add92e 100644
--- a/fs/btrfs/sysfs.h
+++ b/fs/btrfs/sysfs.h
@@ -18,9 +18,7 @@ int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices,
 		struct btrfs_device *one_device);
 int btrfs_sysfs_rm_device_link(struct btrfs_fs_devices *fs_devices,
                 struct btrfs_device *one_device);
-int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs,
-				struct kobject *parent);
-int btrfs_sysfs_add_device(struct btrfs_fs_devices *fs_devs);
+int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs);
 void btrfs_sysfs_remove_fsid(struct btrfs_fs_devices *fs_devs);
 void btrfs_sysfs_update_sprout_fsid(struct btrfs_fs_devices *fs_devices,
 				    const u8 *fsid);
@@ -36,5 +34,6 @@ void btrfs_sysfs_add_block_group_type(struct btrfs_block_group *cache);
 int btrfs_sysfs_add_space_info_type(struct btrfs_fs_info *fs_info,
 				    struct btrfs_space_info *space_info);
 void btrfs_sysfs_remove_space_info(struct btrfs_space_info *space_info);
+void btrfs_sysfs_update_devid(struct btrfs_device *device);
 
 #endif
diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index a7aca4141788..c12b91ff5f56 100644
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -86,6 +86,27 @@ static void btrfs_destroy_test_fs(void)
 	unregister_filesystem(&test_type);
 }
 
+struct btrfs_device *btrfs_alloc_dummy_device(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_device *dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	extent_io_tree_init(NULL, &dev->alloc_state, 0, NULL);
+	INIT_LIST_HEAD(&dev->dev_list);
+	list_add(&dev->dev_list, &fs_info->fs_devices->devices);
+
+	return dev;
+}
+
+static void btrfs_free_dummy_device(struct btrfs_device *dev)
+{
+	extent_io_tree_release(&dev->alloc_state);
+	kfree(dev);
+}
+
 struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize)
 {
 	struct btrfs_fs_info *fs_info = kzalloc(sizeof(struct btrfs_fs_info),
@@ -132,12 +153,14 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize)
 	INIT_LIST_HEAD(&fs_info->dirty_qgroups);
 	INIT_LIST_HEAD(&fs_info->dead_roots);
 	INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
+	INIT_LIST_HEAD(&fs_info->fs_devices->devices);
 	INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC);
 	INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
 	extent_io_tree_init(fs_info, &fs_info->freed_extents[0],
 			    IO_TREE_FS_INFO_FREED_EXTENTS0, NULL);
 	extent_io_tree_init(fs_info, &fs_info->freed_extents[1],
 			    IO_TREE_FS_INFO_FREED_EXTENTS1, NULL);
+	extent_map_tree_init(&fs_info->mapping_tree);
 	fs_info->pinned_extents = &fs_info->freed_extents[0];
 	set_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state);
 
@@ -150,6 +173,7 @@ void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
 {
 	struct radix_tree_iter iter;
 	void **slot;
+	struct btrfs_device *dev, *tmp;
 
 	if (!fs_info)
 		return;
@@ -180,6 +204,11 @@ void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
 	}
 	spin_unlock(&fs_info->buffer_lock);
 
+	btrfs_mapping_tree_free(&fs_info->mapping_tree);
+	list_for_each_entry_safe(dev, tmp, &fs_info->fs_devices->devices,
+				 dev_list) {
+		btrfs_free_dummy_device(dev);
+	}
 	btrfs_free_qgroup_config(fs_info);
 	btrfs_free_fs_roots(fs_info);
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
diff --git a/fs/btrfs/tests/btrfs-tests.h b/fs/btrfs/tests/btrfs-tests.h
index 9e52527357d8..7a2d7ffbe30e 100644
--- a/fs/btrfs/tests/btrfs-tests.h
+++ b/fs/btrfs/tests/btrfs-tests.h
@@ -46,6 +46,7 @@ btrfs_alloc_dummy_block_group(struct btrfs_fs_info *fs_info, unsigned long lengt
 void btrfs_free_dummy_block_group(struct btrfs_block_group *cache);
 void btrfs_init_dummy_trans(struct btrfs_trans_handle *trans,
 			    struct btrfs_fs_info *fs_info);
+struct btrfs_device *btrfs_alloc_dummy_device(struct btrfs_fs_info *fs_info);
 #else
 static inline int btrfs_run_sanity_tests(void)
 {
diff --git a/fs/btrfs/tests/extent-map-tests.c b/fs/btrfs/tests/extent-map-tests.c
index 4a7f796c9900..57379e96ccc9 100644
--- a/fs/btrfs/tests/extent-map-tests.c
+++ b/fs/btrfs/tests/extent-map-tests.c
@@ -6,6 +6,9 @@
 #include <linux/types.h>
 #include "btrfs-tests.h"
 #include "../ctree.h"
+#include "../volumes.h"
+#include "../disk-io.h"
+#include "../block-group.h"
 
 static void free_extent_map_tree(struct extent_map_tree *em_tree)
 {
@@ -437,11 +440,153 @@ static int test_case_4(struct btrfs_fs_info *fs_info,
 	return ret;
 }
 
+struct rmap_test_vector {
+	u64 raid_type;
+	u64 physical_start;
+	u64 data_stripe_size;
+	u64 num_data_stripes;
+	u64 num_stripes;
+	/* Assume we won't have more than 5 physical stripes */
+	u64 data_stripe_phys_start[5];
+	bool expected_mapped_addr;
+	/* Physical to logical addresses */
+	u64 mapped_logical[5];
+};
+
+static int test_rmap_block(struct btrfs_fs_info *fs_info,
+			   struct rmap_test_vector *test)
+{
+	struct extent_map *em;
+	struct map_lookup *map = NULL;
+	u64 *logical = NULL;
+	int i, out_ndaddrs, out_stripe_len;
+	int ret;
+
+	em = alloc_extent_map();
+	if (!em) {
+		test_std_err(TEST_ALLOC_EXTENT_MAP);
+		return -ENOMEM;
+	}
+
+	map = kmalloc(map_lookup_size(test->num_stripes), GFP_KERNEL);
+	if (!map) {
+		kfree(em);
+		test_std_err(TEST_ALLOC_EXTENT_MAP);
+		return -ENOMEM;
+	}
+
+	set_bit(EXTENT_FLAG_FS_MAPPING, &em->flags);
+	/* Start at 4GiB logical address */
+	em->start = SZ_4G;
+	em->len = test->data_stripe_size * test->num_data_stripes;
+	em->block_len = em->len;
+	em->orig_block_len = test->data_stripe_size;
+	em->map_lookup = map;
+
+	map->num_stripes = test->num_stripes;
+	map->stripe_len = BTRFS_STRIPE_LEN;
+	map->type = test->raid_type;
+
+	for (i = 0; i < map->num_stripes; i++) {
+		struct btrfs_device *dev = btrfs_alloc_dummy_device(fs_info);
+
+		if (IS_ERR(dev)) {
+			test_err("cannot allocate device");
+			ret = PTR_ERR(dev);
+			goto out;
+		}
+		map->stripes[i].dev = dev;
+		map->stripes[i].physical = test->data_stripe_phys_start[i];
+	}
+
+	write_lock(&fs_info->mapping_tree.lock);
+	ret = add_extent_mapping(&fs_info->mapping_tree, em, 0);
+	write_unlock(&fs_info->mapping_tree.lock);
+	if (ret) {
+		test_err("error adding block group mapping to mapping tree");
+		goto out_free;
+	}
+
+	ret = btrfs_rmap_block(fs_info, em->start, btrfs_sb_offset(1),
+			       &logical, &out_ndaddrs, &out_stripe_len);
+	if (ret || (out_ndaddrs == 0 && test->expected_mapped_addr)) {
+		test_err("didn't rmap anything but expected %d",
+			 test->expected_mapped_addr);
+		goto out;
+	}
+
+	if (out_stripe_len != BTRFS_STRIPE_LEN) {
+		test_err("calculated stripe length doesn't match");
+		goto out;
+	}
+
+	if (out_ndaddrs != test->expected_mapped_addr) {
+		for (i = 0; i < out_ndaddrs; i++)
+			test_msg("mapped %llu", logical[i]);
+		test_err("unexpected number of mapped addresses: %d", out_ndaddrs);
+		goto out;
+	}
+
+	for (i = 0; i < out_ndaddrs; i++) {
+		if (logical[i] != test->mapped_logical[i]) {
+			test_err("unexpected logical address mapped");
+			goto out;
+		}
+	}
+
+	ret = 0;
+out:
+	write_lock(&fs_info->mapping_tree.lock);
+	remove_extent_mapping(&fs_info->mapping_tree, em);
+	write_unlock(&fs_info->mapping_tree.lock);
+	/* For us */
+	free_extent_map(em);
+out_free:
+	/* For the tree */
+	free_extent_map(em);
+	kfree(logical);
+	return ret;
+}
+
 int btrfs_test_extent_map(void)
 {
 	struct btrfs_fs_info *fs_info = NULL;
 	struct extent_map_tree *em_tree;
-	int ret = 0;
+	int ret = 0, i;
+	struct rmap_test_vector rmap_tests[] = {
+		{
+			/*
+			 * Test a chunk with 2 data stripes one of which
+			 * interesects the physical address of the super block
+			 * is correctly recognised.
+			 */
+			.raid_type = BTRFS_BLOCK_GROUP_RAID1,
+			.physical_start = SZ_64M - SZ_4M,
+			.data_stripe_size = SZ_256M,
+			.num_data_stripes = 2,
+			.num_stripes = 2,
+			.data_stripe_phys_start =
+				{SZ_64M - SZ_4M, SZ_64M - SZ_4M + SZ_256M},
+			.expected_mapped_addr = true,
+			.mapped_logical= {SZ_4G + SZ_4M}
+		},
+		{
+			/*
+			 * Test that out-of-range physical addresses are
+			 * ignored
+			 */
+
+			 /* SINGLE chunk type */
+			.raid_type = 0,
+			.physical_start = SZ_4G,
+			.data_stripe_size = SZ_256M,
+			.num_data_stripes = 1,
+			.num_stripes = 1,
+			.data_stripe_phys_start = {SZ_256M},
+			.expected_mapped_addr = false,
+			.mapped_logical = {0}
+		}
+	};
 
 	test_msg("running extent_map tests");
 
@@ -474,6 +619,13 @@ int btrfs_test_extent_map(void)
 		goto out;
 	ret = test_case_4(fs_info, em_tree);
 
+	test_msg("running rmap tests");
+	for (i = 0; i < ARRAY_SIZE(rmap_tests); i++) {
+		ret = test_rmap_block(fs_info, &rmap_tests[i]);
+		if (ret)
+			goto out;
+	}
+
 out:
 	kfree(em_tree);
 	btrfs_free_dummy_fs_info(fs_info);
diff --git a/fs/btrfs/tests/inode-tests.c b/fs/btrfs/tests/inode-tests.c
index 09ecf7dc7b08..24a8c714f56c 100644
--- a/fs/btrfs/tests/inode-tests.c
+++ b/fs/btrfs/tests/inode-tests.c
@@ -263,7 +263,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 
 	/* First with no extents */
 	BTRFS_I(inode)->root = root;
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, 0, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, 0, sectorsize);
 	if (IS_ERR(em)) {
 		em = NULL;
 		test_err("got an error when we shouldn't have");
@@ -283,7 +283,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	 */
 	setup_file_extents(root, sectorsize);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, 0, (u64)-1, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, 0, (u64)-1);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -305,7 +305,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -333,7 +333,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -356,7 +356,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	free_extent_map(em);
 
 	/* Regular extent */
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -384,7 +384,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	free_extent_map(em);
 
 	/* The next 3 are split extents */
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -413,7 +413,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -435,7 +435,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -469,7 +469,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	free_extent_map(em);
 
 	/* Prealloc extent */
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -498,7 +498,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	free_extent_map(em);
 
 	/* The next 3 are a half written prealloc extent */
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -528,7 +528,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -561,7 +561,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -596,7 +596,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	free_extent_map(em);
 
 	/* Now for the compressed extent */
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -630,7 +630,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	free_extent_map(em);
 
 	/* Split compressed extent */
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -665,7 +665,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -692,7 +692,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -727,8 +727,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	free_extent_map(em);
 
 	/* A hole between regular extents but no hole extent */
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset + 6,
-			sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset + 6, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -755,7 +754,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, SZ_4M, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, SZ_4M);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -788,7 +787,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -872,7 +871,7 @@ static int test_hole_first(u32 sectorsize, u32 nodesize)
 	insert_inode_item_key(root);
 	insert_extent(root, sectorsize, sectorsize, sectorsize, 0, sectorsize,
 		      sectorsize, BTRFS_FILE_EXTENT_REG, 0, 1);
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, 0, 2 * sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, 0, 2 * sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
@@ -894,8 +893,7 @@ static int test_hole_first(u32 sectorsize, u32 nodesize)
 	}
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, sectorsize,
-			2 * sectorsize, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, sectorsize, 2 * sectorsize);
 	if (IS_ERR(em)) {
 		test_err("got an error when we shouldn't have");
 		goto out;
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index cfc08ef9b876..33dcc88b428a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -147,13 +147,14 @@ void btrfs_put_transaction(struct btrfs_transaction *transaction)
 	}
 }
 
-static noinline void switch_commit_roots(struct btrfs_transaction *trans)
+static noinline void switch_commit_roots(struct btrfs_trans_handle *trans)
 {
+	struct btrfs_transaction *cur_trans = trans->transaction;
 	struct btrfs_fs_info *fs_info = trans->fs_info;
 	struct btrfs_root *root, *tmp;
 
 	down_write(&fs_info->commit_root_sem);
-	list_for_each_entry_safe(root, tmp, &trans->switch_commits,
+	list_for_each_entry_safe(root, tmp, &cur_trans->switch_commits,
 				 dirty_list) {
 		list_del_init(&root->dirty_list);
 		free_extent_buffer(root->commit_root);
@@ -165,16 +166,17 @@ static noinline void switch_commit_roots(struct btrfs_transaction *trans)
 	}
 
 	/* We can free old roots now. */
-	spin_lock(&trans->dropped_roots_lock);
-	while (!list_empty(&trans->dropped_roots)) {
-		root = list_first_entry(&trans->dropped_roots,
+	spin_lock(&cur_trans->dropped_roots_lock);
+	while (!list_empty(&cur_trans->dropped_roots)) {
+		root = list_first_entry(&cur_trans->dropped_roots,
 					struct btrfs_root, root_list);
 		list_del_init(&root->root_list);
-		spin_unlock(&trans->dropped_roots_lock);
+		spin_unlock(&cur_trans->dropped_roots_lock);
+		btrfs_free_log(trans, root);
 		btrfs_drop_and_free_fs_root(fs_info, root);
-		spin_lock(&trans->dropped_roots_lock);
+		spin_lock(&cur_trans->dropped_roots_lock);
 	}
-	spin_unlock(&trans->dropped_roots_lock);
+	spin_unlock(&cur_trans->dropped_roots_lock);
 	up_write(&fs_info->commit_root_sem);
 }
 
@@ -1421,7 +1423,7 @@ static int qgroup_account_snapshot(struct btrfs_trans_handle *trans,
 	ret = commit_cowonly_roots(trans);
 	if (ret)
 		goto out;
-	switch_commit_roots(trans->transaction);
+	switch_commit_roots(trans);
 	ret = btrfs_write_and_wait_transaction(trans);
 	if (ret)
 		btrfs_handle_fs_error(fs_info, ret,
@@ -2013,6 +2015,14 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
 	ASSERT(refcount_read(&trans->use_count) == 1);
 
+	/*
+	 * Some places just start a transaction to commit it.  We need to make
+	 * sure that if this commit fails that the abort code actually marks the
+	 * transaction as failed, so set trans->dirty to make the abort code do
+	 * the right thing.
+	 */
+	trans->dirty = true;
+
 	/* Stop the commit early if ->aborted is set */
 	if (unlikely(READ_ONCE(cur_trans->aborted))) {
 		ret = cur_trans->aborted;
@@ -2301,7 +2311,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	list_add_tail(&fs_info->chunk_root->dirty_list,
 		      &cur_trans->switch_commits);
 
-	switch_commit_roots(cur_trans);
+	switch_commit_roots(trans);
 
 	ASSERT(list_empty(&cur_trans->dirty_bgs));
 	ASSERT(list_empty(&cur_trans->io_bgs));
diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 97f3520b8d98..a92f8a6dd192 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -373,6 +373,104 @@ static int check_csum_item(struct extent_buffer *leaf, struct btrfs_key *key,
 	return 0;
 }
 
+/* Inode item error output has the same format as dir_item_err() */
+#define inode_item_err(eb, slot, fmt, ...)			\
+	dir_item_err(eb, slot, fmt, __VA_ARGS__)
+
+static int check_inode_key(struct extent_buffer *leaf, struct btrfs_key *key,
+			   int slot)
+{
+	struct btrfs_key item_key;
+	bool is_inode_item;
+
+	btrfs_item_key_to_cpu(leaf, &item_key, slot);
+	is_inode_item = (item_key.type == BTRFS_INODE_ITEM_KEY);
+
+	/* For XATTR_ITEM, location key should be all 0 */
+	if (item_key.type == BTRFS_XATTR_ITEM_KEY) {
+		if (key->type != 0 || key->objectid != 0 || key->offset != 0)
+			return -EUCLEAN;
+		return 0;
+	}
+
+	if ((key->objectid < BTRFS_FIRST_FREE_OBJECTID ||
+	     key->objectid > BTRFS_LAST_FREE_OBJECTID) &&
+	    key->objectid != BTRFS_ROOT_TREE_DIR_OBJECTID &&
+	    key->objectid != BTRFS_FREE_INO_OBJECTID) {
+		if (is_inode_item) {
+			generic_err(leaf, slot,
+	"invalid key objectid: has %llu expect %llu or [%llu, %llu] or %llu",
+				key->objectid, BTRFS_ROOT_TREE_DIR_OBJECTID,
+				BTRFS_FIRST_FREE_OBJECTID,
+				BTRFS_LAST_FREE_OBJECTID,
+				BTRFS_FREE_INO_OBJECTID);
+		} else {
+			dir_item_err(leaf, slot,
+"invalid location key objectid: has %llu expect %llu or [%llu, %llu] or %llu",
+				key->objectid, BTRFS_ROOT_TREE_DIR_OBJECTID,
+				BTRFS_FIRST_FREE_OBJECTID,
+				BTRFS_LAST_FREE_OBJECTID,
+				BTRFS_FREE_INO_OBJECTID);
+		}
+		return -EUCLEAN;
+	}
+	if (key->offset != 0) {
+		if (is_inode_item)
+			inode_item_err(leaf, slot,
+				       "invalid key offset: has %llu expect 0",
+				       key->offset);
+		else
+			dir_item_err(leaf, slot,
+				"invalid location key offset:has %llu expect 0",
+				key->offset);
+		return -EUCLEAN;
+	}
+	return 0;
+}
+
+static int check_root_key(struct extent_buffer *leaf, struct btrfs_key *key,
+			  int slot)
+{
+	struct btrfs_key item_key;
+	bool is_root_item;
+
+	btrfs_item_key_to_cpu(leaf, &item_key, slot);
+	is_root_item = (item_key.type == BTRFS_ROOT_ITEM_KEY);
+
+	/* No such tree id */
+	if (key->objectid == 0) {
+		if (is_root_item)
+			generic_err(leaf, slot, "invalid root id 0");
+		else
+			dir_item_err(leaf, slot,
+				     "invalid location key root id 0");
+		return -EUCLEAN;
+	}
+
+	/* DIR_ITEM/INDEX/INODE_REF is not allowed to point to non-fs trees */
+	if (!is_fstree(key->objectid) && !is_root_item) {
+		dir_item_err(leaf, slot,
+		"invalid location key objectid, have %llu expect [%llu, %llu]",
+				key->objectid, BTRFS_FIRST_FREE_OBJECTID,
+				BTRFS_LAST_FREE_OBJECTID);
+		return -EUCLEAN;
+	}
+
+	/*
+	 * ROOT_ITEM with non-zero offset means this is a snapshot, created at
+	 * @offset transid.
+	 * Furthermore, for location key in DIR_ITEM, its offset is always -1.
+	 *
+	 * So here we only check offset for reloc tree whose key->offset must
+	 * be a valid tree.
+	 */
+	if (key->objectid == BTRFS_TREE_RELOC_OBJECTID && key->offset == 0) {
+		generic_err(leaf, slot, "invalid root id 0 for reloc tree");
+		return -EUCLEAN;
+	}
+	return 0;
+}
+
 static int check_dir_item(struct extent_buffer *leaf,
 			  struct btrfs_key *key, struct btrfs_key *prev_key,
 			  int slot)
@@ -386,12 +484,14 @@ static int check_dir_item(struct extent_buffer *leaf,
 		return -EUCLEAN;
 	di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 	while (cur < item_size) {
+		struct btrfs_key location_key;
 		u32 name_len;
 		u32 data_len;
 		u32 max_name_len;
 		u32 total_size;
 		u32 name_hash;
 		u8 dir_type;
+		int ret;
 
 		/* header itself should not cross item boundary */
 		if (cur + sizeof(*di) > item_size) {
@@ -401,6 +501,25 @@ static int check_dir_item(struct extent_buffer *leaf,
 			return -EUCLEAN;
 		}
 
+		/* Location key check */
+		btrfs_dir_item_key_to_cpu(leaf, di, &location_key);
+		if (location_key.type == BTRFS_ROOT_ITEM_KEY) {
+			ret = check_root_key(leaf, &location_key, slot);
+			if (ret < 0)
+				return ret;
+		} else if (location_key.type == BTRFS_INODE_ITEM_KEY ||
+			   location_key.type == 0) {
+			ret = check_inode_key(leaf, &location_key, slot);
+			if (ret < 0)
+				return ret;
+		} else {
+			dir_item_err(leaf, slot,
+			"invalid location key type, have %u, expect %u or %u",
+				     location_key.type, BTRFS_ROOT_ITEM_KEY,
+				     BTRFS_INODE_ITEM_KEY);
+			return -EUCLEAN;
+		}
+
 		/* dir type check */
 		dir_type = btrfs_dir_type(leaf, di);
 		if (dir_type >= BTRFS_FT_MAX) {
@@ -738,6 +857,44 @@ int btrfs_check_chunk_valid(struct extent_buffer *leaf,
 	return 0;
 }
 
+/*
+ * Enhanced version of chunk item checker.
+ *
+ * The common btrfs_check_chunk_valid() doesn't check item size since it needs
+ * to work on super block sys_chunk_array which doesn't have full item ptr.
+ */
+static int check_leaf_chunk_item(struct extent_buffer *leaf,
+				 struct btrfs_chunk *chunk,
+				 struct btrfs_key *key, int slot)
+{
+	int num_stripes;
+
+	if (btrfs_item_size_nr(leaf, slot) < sizeof(struct btrfs_chunk)) {
+		chunk_err(leaf, chunk, key->offset,
+			"invalid chunk item size: have %u expect [%zu, %u)",
+			btrfs_item_size_nr(leaf, slot),
+			sizeof(struct btrfs_chunk),
+			BTRFS_LEAF_DATA_SIZE(leaf->fs_info));
+		return -EUCLEAN;
+	}
+
+	num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
+	/* Let btrfs_check_chunk_valid() handle this error type */
+	if (num_stripes == 0)
+		goto out;
+
+	if (btrfs_chunk_item_size(num_stripes) !=
+	    btrfs_item_size_nr(leaf, slot)) {
+		chunk_err(leaf, chunk, key->offset,
+			"invalid chunk item size: have %u expect %lu",
+			btrfs_item_size_nr(leaf, slot),
+			btrfs_chunk_item_size(num_stripes));
+		return -EUCLEAN;
+	}
+out:
+	return btrfs_check_chunk_valid(leaf, chunk, key->offset);
+}
+
 __printf(3, 4)
 __cold
 static void dev_item_err(const struct extent_buffer *eb, int slot,
@@ -801,7 +958,7 @@ static int check_dev_item(struct extent_buffer *leaf,
 }
 
 /* Inode item error output has the same format as dir_item_err() */
-#define inode_item_err(fs_info, eb, slot, fmt, ...)			\
+#define inode_item_err(eb, slot, fmt, ...)			\
 	dir_item_err(eb, slot, fmt, __VA_ARGS__)
 
 static int check_inode_item(struct extent_buffer *leaf,
@@ -812,30 +969,17 @@ static int check_inode_item(struct extent_buffer *leaf,
 	u64 super_gen = btrfs_super_generation(fs_info->super_copy);
 	u32 valid_mask = (S_IFMT | S_ISUID | S_ISGID | S_ISVTX | 0777);
 	u32 mode;
+	int ret;
+
+	ret = check_inode_key(leaf, key, slot);
+	if (ret < 0)
+		return ret;
 
-	if ((key->objectid < BTRFS_FIRST_FREE_OBJECTID ||
-	     key->objectid > BTRFS_LAST_FREE_OBJECTID) &&
-	    key->objectid != BTRFS_ROOT_TREE_DIR_OBJECTID &&
-	    key->objectid != BTRFS_FREE_INO_OBJECTID) {
-		generic_err(leaf, slot,
-	"invalid key objectid: has %llu expect %llu or [%llu, %llu] or %llu",
-			    key->objectid, BTRFS_ROOT_TREE_DIR_OBJECTID,
-			    BTRFS_FIRST_FREE_OBJECTID,
-			    BTRFS_LAST_FREE_OBJECTID,
-			    BTRFS_FREE_INO_OBJECTID);
-		return -EUCLEAN;
-	}
-	if (key->offset != 0) {
-		inode_item_err(fs_info, leaf, slot,
-			"invalid key offset: has %llu expect 0",
-			key->offset);
-		return -EUCLEAN;
-	}
 	iitem = btrfs_item_ptr(leaf, slot, struct btrfs_inode_item);
 
 	/* Here we use super block generation + 1 to handle log tree */
 	if (btrfs_inode_generation(leaf, iitem) > super_gen + 1) {
-		inode_item_err(fs_info, leaf, slot,
+		inode_item_err(leaf, slot,
 			"invalid inode generation: has %llu expect (0, %llu]",
 			       btrfs_inode_generation(leaf, iitem),
 			       super_gen + 1);
@@ -843,7 +987,7 @@ static int check_inode_item(struct extent_buffer *leaf,
 	}
 	/* Note for ROOT_TREE_DIR_ITEM, mkfs could set its transid 0 */
 	if (btrfs_inode_transid(leaf, iitem) > super_gen + 1) {
-		inode_item_err(fs_info, leaf, slot,
+		inode_item_err(leaf, slot,
 			"invalid inode generation: has %llu expect [0, %llu]",
 			       btrfs_inode_transid(leaf, iitem), super_gen + 1);
 		return -EUCLEAN;
@@ -856,7 +1000,7 @@ static int check_inode_item(struct extent_buffer *leaf,
 	 */
 	mode = btrfs_inode_mode(leaf, iitem);
 	if (mode & ~valid_mask) {
-		inode_item_err(fs_info, leaf, slot,
+		inode_item_err(leaf, slot,
 			       "unknown mode bit detected: 0x%x",
 			       mode & ~valid_mask);
 		return -EUCLEAN;
@@ -869,20 +1013,20 @@ static int check_inode_item(struct extent_buffer *leaf,
 	 */
 	if (!has_single_bit_set(mode & S_IFMT)) {
 		if (!S_ISLNK(mode) && !S_ISBLK(mode) && !S_ISSOCK(mode)) {
-			inode_item_err(fs_info, leaf, slot,
+			inode_item_err(leaf, slot,
 			"invalid mode: has 0%o expect valid S_IF* bit(s)",
 				       mode & S_IFMT);
 			return -EUCLEAN;
 		}
 	}
 	if (S_ISDIR(mode) && btrfs_inode_nlink(leaf, iitem) > 1) {
-		inode_item_err(fs_info, leaf, slot,
+		inode_item_err(leaf, slot,
 		       "invalid nlink: has %u expect no more than 1 for dir",
 			btrfs_inode_nlink(leaf, iitem));
 		return -EUCLEAN;
 	}
 	if (btrfs_inode_flags(leaf, iitem) & ~BTRFS_INODE_FLAG_MASK) {
-		inode_item_err(fs_info, leaf, slot,
+		inode_item_err(leaf, slot,
 			       "unknown flags detected: 0x%llx",
 			       btrfs_inode_flags(leaf, iitem) &
 			       ~BTRFS_INODE_FLAG_MASK);
@@ -898,22 +1042,11 @@ static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key,
 	struct btrfs_root_item ri;
 	const u64 valid_root_flags = BTRFS_ROOT_SUBVOL_RDONLY |
 				     BTRFS_ROOT_SUBVOL_DEAD;
+	int ret;
 
-	/* No such tree id */
-	if (key->objectid == 0) {
-		generic_err(leaf, slot, "invalid root id 0");
-		return -EUCLEAN;
-	}
-
-	/*
-	 * Some older kernel may create ROOT_ITEM with non-zero offset, so here
-	 * we only check offset for reloc tree whose key->offset must be a
-	 * valid tree.
-	 */
-	if (key->objectid == BTRFS_TREE_RELOC_OBJECTID && key->offset == 0) {
-		generic_err(leaf, slot, "invalid root id 0 for reloc tree");
-		return -EUCLEAN;
-	}
+	ret = check_root_key(leaf, key, slot);
+	if (ret < 0)
+		return ret;
 
 	if (btrfs_item_size_nr(leaf, slot) != sizeof(ri)) {
 		generic_err(leaf, slot,
@@ -1302,8 +1435,8 @@ static int check_extent_data_ref(struct extent_buffer *leaf,
 	return 0;
 }
 
-#define inode_ref_err(fs_info, eb, slot, fmt, args...)			\
-	inode_item_err(fs_info, eb, slot, fmt, ##args)
+#define inode_ref_err(eb, slot, fmt, args...)			\
+	inode_item_err(eb, slot, fmt, ##args)
 static int check_inode_ref(struct extent_buffer *leaf,
 			   struct btrfs_key *key, struct btrfs_key *prev_key,
 			   int slot)
@@ -1316,7 +1449,7 @@ static int check_inode_ref(struct extent_buffer *leaf,
 		return -EUCLEAN;
 	/* namelen can't be 0, so item_size == sizeof() is also invalid */
 	if (btrfs_item_size_nr(leaf, slot) <= sizeof(*iref)) {
-		inode_ref_err(fs_info, leaf, slot,
+		inode_ref_err(leaf, slot,
 			"invalid item size, have %u expect (%zu, %u)",
 			btrfs_item_size_nr(leaf, slot),
 			sizeof(*iref), BTRFS_LEAF_DATA_SIZE(leaf->fs_info));
@@ -1329,7 +1462,7 @@ static int check_inode_ref(struct extent_buffer *leaf,
 		u16 namelen;
 
 		if (ptr + sizeof(iref) > end) {
-			inode_ref_err(fs_info, leaf, slot,
+			inode_ref_err(leaf, slot,
 			"inode ref overflow, ptr %lu end %lu inode_ref_size %zu",
 				ptr, end, sizeof(iref));
 			return -EUCLEAN;
@@ -1338,7 +1471,7 @@ static int check_inode_ref(struct extent_buffer *leaf,
 		iref = (struct btrfs_inode_ref *)ptr;
 		namelen = btrfs_inode_ref_name_len(leaf, iref);
 		if (ptr + sizeof(*iref) + namelen > end) {
-			inode_ref_err(fs_info, leaf, slot,
+			inode_ref_err(leaf, slot,
 				"inode ref overflow, ptr %lu end %lu namelen %u",
 				ptr, end, namelen);
 			return -EUCLEAN;
@@ -1384,7 +1517,7 @@ static int check_leaf_item(struct extent_buffer *leaf,
 		break;
 	case BTRFS_CHUNK_ITEM_KEY:
 		chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
-		ret = btrfs_check_chunk_valid(leaf, chunk, key->offset);
+		ret = check_leaf_chunk_item(leaf, chunk, key, slot);
 		break;
 	case BTRFS_DEV_ITEM_KEY:
 		ret = check_dev_item(leaf, key, slot);
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index d3f115909ff0..7dd7552f53a4 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2674,14 +2674,9 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 	u32 blocksize;
 	int ret = 0;
 
-	WARN_ON(*level < 0);
-	WARN_ON(*level >= BTRFS_MAX_LEVEL);
-
 	while (*level > 0) {
 		struct btrfs_key first_key;
 
-		WARN_ON(*level < 0);
-		WARN_ON(*level >= BTRFS_MAX_LEVEL);
 		cur = path->nodes[*level];
 
 		WARN_ON(btrfs_header_level(cur) != *level);
@@ -2732,9 +2727,8 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 
 				WARN_ON(root_owner !=
 					BTRFS_TREE_LOG_OBJECTID);
-				ret = btrfs_free_and_pin_reserved_extent(
-							fs_info, bytenr,
-							blocksize);
+				ret = btrfs_pin_reserved_extent(fs_info,
+							bytenr, blocksize);
 				if (ret) {
 					free_extent_buffer(next);
 					return ret;
@@ -2749,7 +2743,6 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 			return ret;
 		}
 
-		WARN_ON(*level <= 0);
 		if (path->nodes[*level-1])
 			free_extent_buffer(path->nodes[*level-1]);
 		path->nodes[*level-1] = next;
@@ -2757,9 +2750,6 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 		path->slots[*level] = 0;
 		cond_resched();
 	}
-	WARN_ON(*level < 0);
-	WARN_ON(*level >= BTRFS_MAX_LEVEL);
-
 	path->slots[*level] = btrfs_header_nritems(path->nodes[*level]);
 
 	cond_resched();
@@ -2815,8 +2805,7 @@ static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
 				}
 
 				WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
-				ret = btrfs_free_and_pin_reserved_extent(
-						fs_info,
+				ret = btrfs_pin_reserved_extent(fs_info,
 						path->nodes[*level]->start,
 						path->nodes[*level]->len);
 				if (ret)
@@ -2896,10 +2885,8 @@ static int walk_log_tree(struct btrfs_trans_handle *trans,
 					clear_extent_buffer_dirty(next);
 			}
 
-			WARN_ON(log->root_key.objectid !=
-				BTRFS_TREE_LOG_OBJECTID);
-			ret = btrfs_free_and_pin_reserved_extent(fs_info,
-							next->start, next->len);
+			ret = btrfs_pin_reserved_extent(fs_info, next->start,
+							next->len);
 			if (ret)
 				goto out;
 		}
@@ -3935,7 +3922,7 @@ static int log_csums(struct btrfs_trans_handle *trans,
 static noinline int copy_items(struct btrfs_trans_handle *trans,
 			       struct btrfs_inode *inode,
 			       struct btrfs_path *dst_path,
-			       struct btrfs_path *src_path, u64 *last_extent,
+			       struct btrfs_path *src_path,
 			       int start_slot, int nr, int inode_only,
 			       u64 logged_isize)
 {
@@ -3946,7 +3933,6 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
 	struct btrfs_file_extent_item *extent;
 	struct btrfs_inode_item *inode_item;
 	struct extent_buffer *src = src_path->nodes[0];
-	struct btrfs_key first_key, last_key, key;
 	int ret;
 	struct btrfs_key *ins_keys;
 	u32 *ins_sizes;
@@ -3954,9 +3940,6 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
 	int i;
 	struct list_head ordered_sums;
 	int skip_csum = inode->flags & BTRFS_INODE_NODATASUM;
-	bool has_extents = false;
-	bool need_find_last_extent = true;
-	bool done = false;
 
 	INIT_LIST_HEAD(&ordered_sums);
 
@@ -3965,8 +3948,6 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
 	if (!ins_data)
 		return -ENOMEM;
 
-	first_key.objectid = (u64)-1;
-
 	ins_sizes = (u32 *)ins_data;
 	ins_keys = (struct btrfs_key *)(ins_data + nr * sizeof(u32));
 
@@ -3987,9 +3968,6 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
 
 		src_offset = btrfs_item_ptr_offset(src, start_slot + i);
 
-		if (i == nr - 1)
-			last_key = ins_keys[i];
-
 		if (ins_keys[i].type == BTRFS_INODE_ITEM_KEY) {
 			inode_item = btrfs_item_ptr(dst_path->nodes[0],
 						    dst_path->slots[0],
@@ -4003,20 +3981,6 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
 					   src_offset, ins_sizes[i]);
 		}
 
-		/*
-		 * We set need_find_last_extent here in case we know we were
-		 * processing other items and then walk into the first extent in
-		 * the inode.  If we don't hit an extent then nothing changes,
-		 * we'll do the last search the next time around.
-		 */
-		if (ins_keys[i].type == BTRFS_EXTENT_DATA_KEY) {
-			has_extents = true;
-			if (first_key.objectid == (u64)-1)
-				first_key = ins_keys[i];
-		} else {
-			need_find_last_extent = false;
-		}
-
 		/* take a reference on file data extents so that truncates
 		 * or deletes of this inode don't have to relog the inode
 		 * again
@@ -4082,167 +4046,6 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
 		kfree(sums);
 	}
 
-	if (!has_extents)
-		return ret;
-
-	if (need_find_last_extent && *last_extent == first_key.offset) {
-		/*
-		 * We don't have any leafs between our current one and the one
-		 * we processed before that can have file extent items for our
-		 * inode (and have a generation number smaller than our current
-		 * transaction id).
-		 */
-		need_find_last_extent = false;
-	}
-
-	/*
-	 * Because we use btrfs_search_forward we could skip leaves that were
-	 * not modified and then assume *last_extent is valid when it really
-	 * isn't.  So back up to the previous leaf and read the end of the last
-	 * extent before we go and fill in holes.
-	 */
-	if (need_find_last_extent) {
-		u64 len;
-
-		ret = btrfs_prev_leaf(inode->root, src_path);
-		if (ret < 0)
-			return ret;
-		if (ret)
-			goto fill_holes;
-		if (src_path->slots[0])
-			src_path->slots[0]--;
-		src = src_path->nodes[0];
-		btrfs_item_key_to_cpu(src, &key, src_path->slots[0]);
-		if (key.objectid != btrfs_ino(inode) ||
-		    key.type != BTRFS_EXTENT_DATA_KEY)
-			goto fill_holes;
-		extent = btrfs_item_ptr(src, src_path->slots[0],
-					struct btrfs_file_extent_item);
-		if (btrfs_file_extent_type(src, extent) ==
-		    BTRFS_FILE_EXTENT_INLINE) {
-			len = btrfs_file_extent_ram_bytes(src, extent);
-			*last_extent = ALIGN(key.offset + len,
-					     fs_info->sectorsize);
-		} else {
-			len = btrfs_file_extent_num_bytes(src, extent);
-			*last_extent = key.offset + len;
-		}
-	}
-fill_holes:
-	/* So we did prev_leaf, now we need to move to the next leaf, but a few
-	 * things could have happened
-	 *
-	 * 1) A merge could have happened, so we could currently be on a leaf
-	 * that holds what we were copying in the first place.
-	 * 2) A split could have happened, and now not all of the items we want
-	 * are on the same leaf.
-	 *
-	 * So we need to adjust how we search for holes, we need to drop the
-	 * path and re-search for the first extent key we found, and then walk
-	 * forward until we hit the last one we copied.
-	 */
-	if (need_find_last_extent) {
-		/* btrfs_prev_leaf could return 1 without releasing the path */
-		btrfs_release_path(src_path);
-		ret = btrfs_search_slot(NULL, inode->root, &first_key,
-				src_path, 0, 0);
-		if (ret < 0)
-			return ret;
-		ASSERT(ret == 0);
-		src = src_path->nodes[0];
-		i = src_path->slots[0];
-	} else {
-		i = start_slot;
-	}
-
-	/*
-	 * Ok so here we need to go through and fill in any holes we may have
-	 * to make sure that holes are punched for those areas in case they had
-	 * extents previously.
-	 */
-	while (!done) {
-		u64 offset, len;
-		u64 extent_end;
-
-		if (i >= btrfs_header_nritems(src_path->nodes[0])) {
-			ret = btrfs_next_leaf(inode->root, src_path);
-			if (ret < 0)
-				return ret;
-			ASSERT(ret == 0);
-			src = src_path->nodes[0];
-			i = 0;
-			need_find_last_extent = true;
-		}
-
-		btrfs_item_key_to_cpu(src, &key, i);
-		if (!btrfs_comp_cpu_keys(&key, &last_key))
-			done = true;
-		if (key.objectid != btrfs_ino(inode) ||
-		    key.type != BTRFS_EXTENT_DATA_KEY) {
-			i++;
-			continue;
-		}
-		extent = btrfs_item_ptr(src, i, struct btrfs_file_extent_item);
-		if (btrfs_file_extent_type(src, extent) ==
-		    BTRFS_FILE_EXTENT_INLINE) {
-			len = btrfs_file_extent_ram_bytes(src, extent);
-			extent_end = ALIGN(key.offset + len,
-					   fs_info->sectorsize);
-		} else {
-			len = btrfs_file_extent_num_bytes(src, extent);
-			extent_end = key.offset + len;
-		}
-		i++;
-
-		if (*last_extent == key.offset) {
-			*last_extent = extent_end;
-			continue;
-		}
-		offset = *last_extent;
-		len = key.offset - *last_extent;
-		ret = btrfs_insert_file_extent(trans, log, btrfs_ino(inode),
-				offset, 0, 0, len, 0, len, 0, 0, 0);
-		if (ret)
-			break;
-		*last_extent = extent_end;
-	}
-
-	/*
-	 * Check if there is a hole between the last extent found in our leaf
-	 * and the first extent in the next leaf. If there is one, we need to
-	 * log an explicit hole so that at replay time we can punch the hole.
-	 */
-	if (ret == 0 &&
-	    key.objectid == btrfs_ino(inode) &&
-	    key.type == BTRFS_EXTENT_DATA_KEY &&
-	    i == btrfs_header_nritems(src_path->nodes[0])) {
-		ret = btrfs_next_leaf(inode->root, src_path);
-		need_find_last_extent = true;
-		if (ret > 0) {
-			ret = 0;
-		} else if (ret == 0) {
-			btrfs_item_key_to_cpu(src_path->nodes[0], &key,
-					      src_path->slots[0]);
-			if (key.objectid == btrfs_ino(inode) &&
-			    key.type == BTRFS_EXTENT_DATA_KEY &&
-			    *last_extent < key.offset) {
-				const u64 len = key.offset - *last_extent;
-
-				ret = btrfs_insert_file_extent(trans, log,
-							       btrfs_ino(inode),
-							       *last_extent, 0,
-							       0, len, 0, len,
-							       0, 0, 0);
-				*last_extent += len;
-			}
-		}
-	}
-	/*
-	 * Need to let the callers know we dropped the path so they should
-	 * re-search.
-	 */
-	if (!ret && need_find_last_extent)
-		ret = 1;
 	return ret;
 }
 
@@ -4407,7 +4210,7 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans,
 	const u64 i_size = i_size_read(&inode->vfs_inode);
 	const u64 ino = btrfs_ino(inode);
 	struct btrfs_path *dst_path = NULL;
-	u64 last_extent = (u64)-1;
+	bool dropped_extents = false;
 	int ins_nr = 0;
 	int start_slot;
 	int ret;
@@ -4429,8 +4232,7 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans,
 		if (slot >= btrfs_header_nritems(leaf)) {
 			if (ins_nr > 0) {
 				ret = copy_items(trans, inode, dst_path, path,
-						 &last_extent, start_slot,
-						 ins_nr, 1, 0);
+						 start_slot, ins_nr, 1, 0);
 				if (ret < 0)
 					goto out;
 				ins_nr = 0;
@@ -4454,8 +4256,7 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans,
 			path->slots[0]++;
 			continue;
 		}
-		if (last_extent == (u64)-1) {
-			last_extent = key.offset;
+		if (!dropped_extents) {
 			/*
 			 * Avoid logging extent items logged in past fsync calls
 			 * and leading to duplicate keys in the log tree.
@@ -4469,6 +4270,7 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans,
 			} while (ret == -EAGAIN);
 			if (ret)
 				goto out;
+			dropped_extents = true;
 		}
 		if (ins_nr == 0)
 			start_slot = slot;
@@ -4483,7 +4285,7 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans,
 		}
 	}
 	if (ins_nr > 0) {
-		ret = copy_items(trans, inode, dst_path, path, &last_extent,
+		ret = copy_items(trans, inode, dst_path, path,
 				 start_slot, ins_nr, 1, 0);
 		if (ret > 0)
 			ret = 0;
@@ -4670,13 +4472,8 @@ static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans,
 
 		if (slot >= nritems) {
 			if (ins_nr > 0) {
-				u64 last_extent = 0;
-
 				ret = copy_items(trans, inode, dst_path, path,
-						 &last_extent, start_slot,
-						 ins_nr, 1, 0);
-				/* can't be 1, extent items aren't processed */
-				ASSERT(ret <= 0);
+						 start_slot, ins_nr, 1, 0);
 				if (ret < 0)
 					return ret;
 				ins_nr = 0;
@@ -4700,13 +4497,8 @@ static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans,
 		cond_resched();
 	}
 	if (ins_nr > 0) {
-		u64 last_extent = 0;
-
 		ret = copy_items(trans, inode, dst_path, path,
-				 &last_extent, start_slot,
-				 ins_nr, 1, 0);
-		/* can't be 1, extent items aren't processed */
-		ASSERT(ret <= 0);
+				 start_slot, ins_nr, 1, 0);
 		if (ret < 0)
 			return ret;
 	}
@@ -4715,100 +4507,119 @@ static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans,
 }
 
 /*
- * If the no holes feature is enabled we need to make sure any hole between the
- * last extent and the i_size of our inode is explicitly marked in the log. This
- * is to make sure that doing something like:
- *
- *      1) create file with 128Kb of data
- *      2) truncate file to 64Kb
- *      3) truncate file to 256Kb
- *      4) fsync file
- *      5) <crash/power failure>
- *      6) mount fs and trigger log replay
- *
- * Will give us a file with a size of 256Kb, the first 64Kb of data match what
- * the file had in its first 64Kb of data at step 1 and the last 192Kb of the
- * file correspond to a hole. The presence of explicit holes in a log tree is
- * what guarantees that log replay will remove/adjust file extent items in the
- * fs/subvol tree.
- *
- * Here we do not need to care about holes between extents, that is already done
- * by copy_items(). We also only need to do this in the full sync path, where we
- * lookup for extents from the fs/subvol tree only. In the fast path case, we
- * lookup the list of modified extent maps and if any represents a hole, we
- * insert a corresponding extent representing a hole in the log tree.
+ * When using the NO_HOLES feature if we punched a hole that causes the
+ * deletion of entire leafs or all the extent items of the first leaf (the one
+ * that contains the inode item and references) we may end up not processing
+ * any extents, because there are no leafs with a generation matching the
+ * current transaction that have extent items for our inode. So we need to find
+ * if any holes exist and then log them. We also need to log holes after any
+ * truncate operation that changes the inode's size.
  */
-static int btrfs_log_trailing_hole(struct btrfs_trans_handle *trans,
-				   struct btrfs_root *root,
-				   struct btrfs_inode *inode,
-				   struct btrfs_path *path)
+static int btrfs_log_holes(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root,
+			   struct btrfs_inode *inode,
+			   struct btrfs_path *path)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
-	int ret;
 	struct btrfs_key key;
-	u64 hole_start;
-	u64 hole_size;
-	struct extent_buffer *leaf;
-	struct btrfs_root *log = root->log_root;
 	const u64 ino = btrfs_ino(inode);
 	const u64 i_size = i_size_read(&inode->vfs_inode);
+	u64 prev_extent_end = 0;
+	int ret;
 
-	if (!btrfs_fs_incompat(fs_info, NO_HOLES))
+	if (!btrfs_fs_incompat(fs_info, NO_HOLES) || i_size == 0)
 		return 0;
 
 	key.objectid = ino;
 	key.type = BTRFS_EXTENT_DATA_KEY;
-	key.offset = (u64)-1;
+	key.offset = 0;
 
 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	ASSERT(ret != 0);
 	if (ret < 0)
 		return ret;
 
-	ASSERT(path->slots[0] > 0);
-	path->slots[0]--;
-	leaf = path->nodes[0];
-	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
-
-	if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) {
-		/* inode does not have any extents */
-		hole_start = 0;
-		hole_size = i_size;
-	} else {
+	while (true) {
 		struct btrfs_file_extent_item *extent;
+		struct extent_buffer *leaf = path->nodes[0];
 		u64 len;
 
-		/*
-		 * If there's an extent beyond i_size, an explicit hole was
-		 * already inserted by copy_items().
-		 */
-		if (key.offset >= i_size)
-			return 0;
+		if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				return ret;
+			if (ret > 0) {
+				ret = 0;
+				break;
+			}
+			leaf = path->nodes[0];
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+		if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
+			break;
+
+		/* We have a hole, log it. */
+		if (prev_extent_end < key.offset) {
+			const u64 hole_len = key.offset - prev_extent_end;
+
+			/*
+			 * Release the path to avoid deadlocks with other code
+			 * paths that search the root while holding locks on
+			 * leafs from the log root.
+			 */
+			btrfs_release_path(path);
+			ret = btrfs_insert_file_extent(trans, root->log_root,
+						       ino, prev_extent_end, 0,
+						       0, hole_len, 0, hole_len,
+						       0, 0, 0);
+			if (ret < 0)
+				return ret;
+
+			/*
+			 * Search for the same key again in the root. Since it's
+			 * an extent item and we are holding the inode lock, the
+			 * key must still exist. If it doesn't just emit warning
+			 * and return an error to fall back to a transaction
+			 * commit.
+			 */
+			ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+			if (ret < 0)
+				return ret;
+			if (WARN_ON(ret > 0))
+				return -ENOENT;
+			leaf = path->nodes[0];
+		}
 
 		extent = btrfs_item_ptr(leaf, path->slots[0],
 					struct btrfs_file_extent_item);
-
 		if (btrfs_file_extent_type(leaf, extent) ==
-		    BTRFS_FILE_EXTENT_INLINE)
-			return 0;
+		    BTRFS_FILE_EXTENT_INLINE) {
+			len = btrfs_file_extent_ram_bytes(leaf, extent);
+			prev_extent_end = ALIGN(key.offset + len,
+						fs_info->sectorsize);
+		} else {
+			len = btrfs_file_extent_num_bytes(leaf, extent);
+			prev_extent_end = key.offset + len;
+		}
 
-		len = btrfs_file_extent_num_bytes(leaf, extent);
-		/* Last extent goes beyond i_size, no need to log a hole. */
-		if (key.offset + len > i_size)
-			return 0;
-		hole_start = key.offset + len;
-		hole_size = i_size - hole_start;
+		path->slots[0]++;
+		cond_resched();
 	}
-	btrfs_release_path(path);
 
-	/* Last extent ends at i_size. */
-	if (hole_size == 0)
-		return 0;
+	if (prev_extent_end < i_size) {
+		u64 hole_len;
 
-	hole_size = ALIGN(hole_size, fs_info->sectorsize);
-	ret = btrfs_insert_file_extent(trans, log, ino, hole_start, 0, 0,
-				       hole_size, 0, hole_size, 0, 0, 0);
-	return ret;
+		btrfs_release_path(path);
+		hole_len = ALIGN(i_size - prev_extent_end, fs_info->sectorsize);
+		ret = btrfs_insert_file_extent(trans, root->log_root,
+					       ino, prev_extent_end, 0, 0,
+					       hole_len, 0, hole_len,
+					       0, 0, 0);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
 }
 
 /*
@@ -5012,6 +4823,50 @@ static int log_conflicting_inodes(struct btrfs_trans_handle *trans,
 			continue;
 		}
 		/*
+		 * If the inode was already logged skip it - otherwise we can
+		 * hit an infinite loop. Example:
+		 *
+		 * From the commit root (previous transaction) we have the
+		 * following inodes:
+		 *
+		 * inode 257 a directory
+		 * inode 258 with references "zz" and "zz_link" on inode 257
+		 * inode 259 with reference "a" on inode 257
+		 *
+		 * And in the current (uncommitted) transaction we have:
+		 *
+		 * inode 257 a directory, unchanged
+		 * inode 258 with references "a" and "a2" on inode 257
+		 * inode 259 with reference "zz_link" on inode 257
+		 * inode 261 with reference "zz" on inode 257
+		 *
+		 * When logging inode 261 the following infinite loop could
+		 * happen if we don't skip already logged inodes:
+		 *
+		 * - we detect inode 258 as a conflicting inode, with inode 261
+		 *   on reference "zz", and log it;
+		 *
+		 * - we detect inode 259 as a conflicting inode, with inode 258
+		 *   on reference "a", and log it;
+		 *
+		 * - we detect inode 258 as a conflicting inode, with inode 259
+		 *   on reference "zz_link", and log it - again! After this we
+		 *   repeat the above steps forever.
+		 */
+		spin_lock(&BTRFS_I(inode)->lock);
+		/*
+		 * Check the inode's logged_trans only instead of
+		 * btrfs_inode_in_log(). This is because the last_log_commit of
+		 * the inode is not updated when we only log that it exists and
+		 * and it has the full sync bit set (see btrfs_log_inode()).
+		 */
+		if (BTRFS_I(inode)->logged_trans == trans->transid) {
+			spin_unlock(&BTRFS_I(inode)->lock);
+			btrfs_add_delayed_iput(inode);
+			continue;
+		}
+		spin_unlock(&BTRFS_I(inode)->lock);
+		/*
 		 * We are safe logging the other inode without acquiring its
 		 * lock as long as we log with the LOG_INODE_EXISTS mode. We
 		 * are safe against concurrent renames of the other inode as
@@ -5110,7 +4965,6 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans,
 	struct btrfs_key min_key;
 	struct btrfs_key max_key;
 	struct btrfs_root *log = root->log_root;
-	u64 last_extent = 0;
 	int err = 0;
 	int ret;
 	int nritems;
@@ -5288,7 +5142,7 @@ again:
 					ins_start_slot = path->slots[0];
 				}
 				ret = copy_items(trans, inode, dst_path, path,
-						 &last_extent, ins_start_slot,
+						 ins_start_slot,
 						 ins_nr, inode_only,
 						 logged_isize);
 				if (ret < 0) {
@@ -5311,17 +5165,13 @@ again:
 			if (ins_nr == 0)
 				goto next_slot;
 			ret = copy_items(trans, inode, dst_path, path,
-					 &last_extent, ins_start_slot,
+					 ins_start_slot,
 					 ins_nr, inode_only, logged_isize);
 			if (ret < 0) {
 				err = ret;
 				goto out_unlock;
 			}
 			ins_nr = 0;
-			if (ret) {
-				btrfs_release_path(path);
-				continue;
-			}
 			goto next_slot;
 		}
 
@@ -5334,18 +5184,13 @@ again:
 			goto next_slot;
 		}
 
-		ret = copy_items(trans, inode, dst_path, path, &last_extent,
+		ret = copy_items(trans, inode, dst_path, path,
 				 ins_start_slot, ins_nr, inode_only,
 				 logged_isize);
 		if (ret < 0) {
 			err = ret;
 			goto out_unlock;
 		}
-		if (ret) {
-			ins_nr = 0;
-			btrfs_release_path(path);
-			continue;
-		}
 		ins_nr = 1;
 		ins_start_slot = path->slots[0];
 next_slot:
@@ -5359,13 +5204,12 @@ next_slot:
 		}
 		if (ins_nr) {
 			ret = copy_items(trans, inode, dst_path, path,
-					 &last_extent, ins_start_slot,
+					 ins_start_slot,
 					 ins_nr, inode_only, logged_isize);
 			if (ret < 0) {
 				err = ret;
 				goto out_unlock;
 			}
-			ret = 0;
 			ins_nr = 0;
 		}
 		btrfs_release_path(path);
@@ -5380,14 +5224,13 @@ next_key:
 		}
 	}
 	if (ins_nr) {
-		ret = copy_items(trans, inode, dst_path, path, &last_extent,
+		ret = copy_items(trans, inode, dst_path, path,
 				 ins_start_slot, ins_nr, inode_only,
 				 logged_isize);
 		if (ret < 0) {
 			err = ret;
 			goto out_unlock;
 		}
-		ret = 0;
 		ins_nr = 0;
 	}
 
@@ -5400,7 +5243,7 @@ next_key:
 	if (max_key.type >= BTRFS_EXTENT_DATA_KEY && !fast_search) {
 		btrfs_release_path(path);
 		btrfs_release_path(dst_path);
-		err = btrfs_log_trailing_hole(trans, root, inode, path);
+		err = btrfs_log_holes(trans, root, inode, path);
 		if (err)
 			goto out_unlock;
 	}
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9b78e720c697..9cfc668f91f4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -30,6 +30,7 @@
 #include "tree-checker.h"
 #include "space-info.h"
 #include "block-group.h"
+#include "discard.h"
 
 const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
 	[BTRFS_RAID_RAID10] = {
@@ -66,6 +67,7 @@ const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
 		.tolerated_failures = 2,
 		.devs_increment	= 3,
 		.ncopies	= 3,
+		.nparity        = 0,
 		.raid_name	= "raid1c3",
 		.bg_flag	= BTRFS_BLOCK_GROUP_RAID1C3,
 		.mindev_error	= BTRFS_ERROR_DEV_RAID1C3_MIN_NOT_MET,
@@ -78,6 +80,7 @@ const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
 		.tolerated_failures = 3,
 		.devs_increment	= 4,
 		.ncopies	= 4,
+		.nparity        = 0,
 		.raid_name	= "raid1c4",
 		.bg_flag	= BTRFS_BLOCK_GROUP_RAID1C4,
 		.mindev_error	= BTRFS_ERROR_DEV_RAID1C4_MIN_NOT_MET,
@@ -438,39 +441,6 @@ static noinline struct btrfs_fs_devices *find_fsid(
 
 	ASSERT(fsid);
 
-	if (metadata_fsid) {
-		/*
-		 * Handle scanned device having completed its fsid change but
-		 * belonging to a fs_devices that was created by first scanning
-		 * a device which didn't have its fsid/metadata_uuid changed
-		 * at all and the CHANGING_FSID_V2 flag set.
-		 */
-		list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
-			if (fs_devices->fsid_change &&
-			    memcmp(metadata_fsid, fs_devices->fsid,
-				   BTRFS_FSID_SIZE) == 0 &&
-			    memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
-				   BTRFS_FSID_SIZE) == 0) {
-				return fs_devices;
-			}
-		}
-		/*
-		 * Handle scanned device having completed its fsid change but
-		 * belonging to a fs_devices that was created by a device that
-		 * has an outdated pair of fsid/metadata_uuid and
-		 * CHANGING_FSID_V2 flag set.
-		 */
-		list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
-			if (fs_devices->fsid_change &&
-			    memcmp(fs_devices->metadata_uuid,
-				   fs_devices->fsid, BTRFS_FSID_SIZE) != 0 &&
-			    memcmp(metadata_fsid, fs_devices->metadata_uuid,
-				   BTRFS_FSID_SIZE) == 0) {
-				return fs_devices;
-			}
-		}
-	}
-
 	/* Handle non-split brain cases */
 	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
 		if (metadata_fsid) {
@@ -486,6 +456,47 @@ static noinline struct btrfs_fs_devices *find_fsid(
 	return NULL;
 }
 
+static struct btrfs_fs_devices *find_fsid_with_metadata_uuid(
+				struct btrfs_super_block *disk_super)
+{
+
+	struct btrfs_fs_devices *fs_devices;
+
+	/*
+	 * Handle scanned device having completed its fsid change but
+	 * belonging to a fs_devices that was created by first scanning
+	 * a device which didn't have its fsid/metadata_uuid changed
+	 * at all and the CHANGING_FSID_V2 flag set.
+	 */
+	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		if (fs_devices->fsid_change &&
+		    memcmp(disk_super->metadata_uuid, fs_devices->fsid,
+			   BTRFS_FSID_SIZE) == 0 &&
+		    memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
+			   BTRFS_FSID_SIZE) == 0) {
+			return fs_devices;
+		}
+	}
+	/*
+	 * Handle scanned device having completed its fsid change but
+	 * belonging to a fs_devices that was created by a device that
+	 * has an outdated pair of fsid/metadata_uuid and
+	 * CHANGING_FSID_V2 flag set.
+	 */
+	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		if (fs_devices->fsid_change &&
+		    memcmp(fs_devices->metadata_uuid,
+			   fs_devices->fsid, BTRFS_FSID_SIZE) != 0 &&
+		    memcmp(disk_super->metadata_uuid, fs_devices->metadata_uuid,
+			   BTRFS_FSID_SIZE) == 0) {
+			return fs_devices;
+		}
+	}
+
+	return find_fsid(disk_super->fsid, disk_super->metadata_uuid);
+}
+
+
 static int
 btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder,
 		      int flush, struct block_device **bdev,
@@ -669,7 +680,9 @@ error_brelse:
 
 /*
  * Handle scanned device having its CHANGING_FSID_V2 flag set and the fs_devices
- * being created with a disk that has already completed its fsid change.
+ * being created with a disk that has already completed its fsid change. Such
+ * disk can belong to an fs which has its FSID changed or to one which doesn't.
+ * Handle both cases here.
  */
 static struct btrfs_fs_devices *find_fsid_inprogress(
 					struct btrfs_super_block *disk_super)
@@ -685,7 +698,7 @@ static struct btrfs_fs_devices *find_fsid_inprogress(
 		}
 	}
 
-	return NULL;
+	return find_fsid(disk_super->fsid, NULL);
 }
 
 
@@ -697,17 +710,54 @@ static struct btrfs_fs_devices *find_fsid_changed(
 	/*
 	 * Handles the case where scanned device is part of an fs that had
 	 * multiple successful changes of FSID but curently device didn't
-	 * observe it. Meaning our fsid will be different than theirs.
+	 * observe it. Meaning our fsid will be different than theirs. We need
+	 * to handle two subcases :
+	 *  1 - The fs still continues to have different METADATA/FSID uuids.
+	 *  2 - The fs is switched back to its original FSID (METADATA/FSID
+	 *  are equal).
 	 */
 	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		/* Changed UUIDs */
 		if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
 			   BTRFS_FSID_SIZE) != 0 &&
 		    memcmp(fs_devices->metadata_uuid, disk_super->metadata_uuid,
 			   BTRFS_FSID_SIZE) == 0 &&
 		    memcmp(fs_devices->fsid, disk_super->fsid,
-			   BTRFS_FSID_SIZE) != 0) {
+			   BTRFS_FSID_SIZE) != 0)
+			return fs_devices;
+
+		/* Unchanged UUIDs */
+		if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
+			   BTRFS_FSID_SIZE) == 0 &&
+		    memcmp(fs_devices->fsid, disk_super->metadata_uuid,
+			   BTRFS_FSID_SIZE) == 0)
+			return fs_devices;
+	}
+
+	return NULL;
+}
+
+static struct btrfs_fs_devices *find_fsid_reverted_metadata(
+				struct btrfs_super_block *disk_super)
+{
+	struct btrfs_fs_devices *fs_devices;
+
+	/*
+	 * Handle the case where the scanned device is part of an fs whose last
+	 * metadata UUID change reverted it to the original FSID. At the same
+	 * time * fs_devices was first created by another constitutent device
+	 * which didn't fully observe the operation. This results in an
+	 * btrfs_fs_devices created with metadata/fsid different AND
+	 * btrfs_fs_devices::fsid_change set AND the metadata_uuid of the
+	 * fs_devices equal to the FSID of the disk.
+	 */
+	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		if (memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
+			   BTRFS_FSID_SIZE) != 0 &&
+		    memcmp(fs_devices->metadata_uuid, disk_super->fsid,
+			   BTRFS_FSID_SIZE) == 0 &&
+		    fs_devices->fsid_change)
 			return fs_devices;
-		}
 	}
 
 	return NULL;
@@ -734,24 +784,16 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 					BTRFS_SUPER_FLAG_CHANGING_FSID_V2);
 
 	if (fsid_change_in_progress) {
-		if (!has_metadata_uuid) {
-			/*
-			 * When we have an image which has CHANGING_FSID_V2 set
-			 * it might belong to either a filesystem which has
-			 * disks with completed fsid change or it might belong
-			 * to fs with no UUID changes in effect, handle both.
-			 */
+		if (!has_metadata_uuid)
 			fs_devices = find_fsid_inprogress(disk_super);
-			if (!fs_devices)
-				fs_devices = find_fsid(disk_super->fsid, NULL);
-		} else {
+		else
 			fs_devices = find_fsid_changed(disk_super);
-		}
 	} else if (has_metadata_uuid) {
-		fs_devices = find_fsid(disk_super->fsid,
-				       disk_super->metadata_uuid);
+		fs_devices = find_fsid_with_metadata_uuid(disk_super);
 	} else {
-		fs_devices = find_fsid(disk_super->fsid, NULL);
+		fs_devices = find_fsid_reverted_metadata(disk_super);
+		if (!fs_devices)
+			fs_devices = find_fsid(disk_super->fsid, NULL);
 	}
 
 
@@ -781,12 +823,18 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 		 * a device which had the CHANGING_FSID_V2 flag then replace the
 		 * metadata_uuid/fsid values of the fs_devices.
 		 */
-		if (has_metadata_uuid && fs_devices->fsid_change &&
+		if (fs_devices->fsid_change &&
 		    found_transid > fs_devices->latest_generation) {
 			memcpy(fs_devices->fsid, disk_super->fsid,
 					BTRFS_FSID_SIZE);
-			memcpy(fs_devices->metadata_uuid,
-					disk_super->metadata_uuid, BTRFS_FSID_SIZE);
+
+			if (has_metadata_uuid)
+				memcpy(fs_devices->metadata_uuid,
+				       disk_super->metadata_uuid,
+				       BTRFS_FSID_SIZE);
+			else
+				memcpy(fs_devices->metadata_uuid,
+				       disk_super->fsid, BTRFS_FSID_SIZE);
 
 			fs_devices->fsid_change = false;
 		}
@@ -1064,11 +1112,6 @@ static void btrfs_close_bdev(struct btrfs_device *device)
 static void btrfs_close_one_device(struct btrfs_device *device)
 {
 	struct btrfs_fs_devices *fs_devices = device->fs_devices;
-	struct btrfs_device *new_device;
-	struct rcu_string *name;
-
-	if (device->bdev)
-		fs_devices->open_devices--;
 
 	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
 	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
@@ -1080,23 +1123,22 @@ static void btrfs_close_one_device(struct btrfs_device *device)
 		fs_devices->missing_devices--;
 
 	btrfs_close_bdev(device);
-
-	new_device = btrfs_alloc_device(NULL, &device->devid,
-					device->uuid);
-	BUG_ON(IS_ERR(new_device)); /* -ENOMEM */
-
-	/* Safe because we are under uuid_mutex */
-	if (device->name) {
-		name = rcu_string_strdup(device->name->str, GFP_NOFS);
-		BUG_ON(!name); /* -ENOMEM */
-		rcu_assign_pointer(new_device->name, name);
+	if (device->bdev) {
+		fs_devices->open_devices--;
+		device->bdev = NULL;
 	}
+	clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 
-	list_replace_rcu(&device->dev_list, &new_device->dev_list);
-	new_device->fs_devices = device->fs_devices;
+	device->fs_info = NULL;
+	atomic_set(&device->dev_stats_ccnt, 0);
+	extent_io_tree_release(&device->alloc_state);
 
-	synchronize_rcu();
-	btrfs_free_device(device);
+	/* Verify the device is back in a pristine state  */
+	ASSERT(!test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state));
+	ASSERT(!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state));
+	ASSERT(list_empty(&device->dev_alloc_list));
+	ASSERT(list_empty(&device->post_commit_list));
+	ASSERT(atomic_read(&device->reada_in_flight) == 0);
 }
 
 static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
@@ -2130,7 +2172,6 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
 {
 	struct btrfs_fs_devices *fs_devices = tgtdev->fs_info->fs_devices;
 
-	WARN_ON(!tgtdev);
 	mutex_lock(&fs_devices->device_list_mutex);
 
 	btrfs_sysfs_rm_device_link(fs_devices, tgtdev);
@@ -2875,6 +2916,7 @@ static int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
 {
 	struct btrfs_root *root = fs_info->chunk_root;
 	struct btrfs_trans_handle *trans;
+	struct btrfs_block_group *block_group;
 	int ret;
 
 	/*
@@ -2898,6 +2940,12 @@ static int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
 	if (ret)
 		return ret;
 
+	block_group = btrfs_lookup_block_group(fs_info, chunk_offset);
+	if (!block_group)
+		return -ENOENT;
+	btrfs_discard_cancel_work(&fs_info->discard_ctl, block_group);
+	btrfs_put_block_group(block_group);
+
 	trans = btrfs_start_trans_remove_block_group(root->fs_info,
 						     chunk_offset);
 	if (IS_ERR(trans)) {
@@ -6111,75 +6159,6 @@ int btrfs_map_sblock(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 	return __btrfs_map_block(fs_info, op, logical, length, bbio_ret, 0, 1);
 }
 
-int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
-		     u64 physical, u64 **logical, int *naddrs, int *stripe_len)
-{
-	struct extent_map *em;
-	struct map_lookup *map;
-	u64 *buf;
-	u64 bytenr;
-	u64 length;
-	u64 stripe_nr;
-	u64 rmap_len;
-	int i, j, nr = 0;
-
-	em = btrfs_get_chunk_map(fs_info, chunk_start, 1);
-	if (IS_ERR(em))
-		return -EIO;
-
-	map = em->map_lookup;
-	length = em->len;
-	rmap_len = map->stripe_len;
-
-	if (map->type & BTRFS_BLOCK_GROUP_RAID10)
-		length = div_u64(length, map->num_stripes / map->sub_stripes);
-	else if (map->type & BTRFS_BLOCK_GROUP_RAID0)
-		length = div_u64(length, map->num_stripes);
-	else if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
-		length = div_u64(length, nr_data_stripes(map));
-		rmap_len = map->stripe_len * nr_data_stripes(map);
-	}
-
-	buf = kcalloc(map->num_stripes, sizeof(u64), GFP_NOFS);
-	BUG_ON(!buf); /* -ENOMEM */
-
-	for (i = 0; i < map->num_stripes; i++) {
-		if (map->stripes[i].physical > physical ||
-		    map->stripes[i].physical + length <= physical)
-			continue;
-
-		stripe_nr = physical - map->stripes[i].physical;
-		stripe_nr = div64_u64(stripe_nr, map->stripe_len);
-
-		if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
-			stripe_nr = stripe_nr * map->num_stripes + i;
-			stripe_nr = div_u64(stripe_nr, map->sub_stripes);
-		} else if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
-			stripe_nr = stripe_nr * map->num_stripes + i;
-		} /* else if RAID[56], multiply by nr_data_stripes().
-		   * Alternatively, just use rmap_len below instead of
-		   * map->stripe_len */
-
-		bytenr = chunk_start + stripe_nr * rmap_len;
-		WARN_ON(nr >= map->num_stripes);
-		for (j = 0; j < nr; j++) {
-			if (buf[j] == bytenr)
-				break;
-		}
-		if (j == nr) {
-			WARN_ON(nr >= map->num_stripes);
-			buf[nr++] = bytenr;
-		}
-	}
-
-	*logical = buf;
-	*naddrs = nr;
-	*stripe_len = rmap_len;
-
-	free_extent_map(em);
-	return 0;
-}
-
 static inline void btrfs_end_bbio(struct btrfs_bio *bbio, struct bio *bio)
 {
 	bio->bi_private = bbio->private;
@@ -6480,19 +6459,14 @@ static u64 calc_stripe_length(u64 type, u64 chunk_len, int num_stripes)
 {
 	int index = btrfs_bg_flags_to_raid_index(type);
 	int ncopies = btrfs_raid_array[index].ncopies;
+	const int nparity = btrfs_raid_array[index].nparity;
 	int data_stripes;
 
-	switch (type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
-	case BTRFS_BLOCK_GROUP_RAID5:
-		data_stripes = num_stripes - 1;
-		break;
-	case BTRFS_BLOCK_GROUP_RAID6:
-		data_stripes = num_stripes - 2;
-		break;
-	default:
+	if (nparity)
+		data_stripes = num_stripes - nparity;
+	else
 		data_stripes = num_stripes / ncopies;
-		break;
-	}
+
 	return div_u64(chunk_len, data_stripes);
 }
 
@@ -7331,6 +7305,8 @@ int btrfs_get_dev_stats(struct btrfs_fs_info *fs_info,
 			else
 				btrfs_dev_stat_set(dev, i, 0);
 		}
+		btrfs_info(fs_info, "device stats zeroed by %s (%d)",
+			   current->comm, task_pid_nr(current));
 	} else {
 		for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
 			if (stats->nr_items > i)
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 0ee5386926fa..409f4816fb89 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -120,8 +120,6 @@ struct btrfs_device {
 	/* per-device scrub information */
 	struct scrub_ctx *scrub_ctx;
 
-	struct btrfs_work work;
-
 	/* readahead state */
 	atomic_t reada_in_flight;
 	u64 reada_next;
@@ -138,6 +136,10 @@ struct btrfs_device {
 	atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
 
 	struct extent_io_tree alloc_state;
+
+	struct completion kobj_unregister;
+	/* For sysfs/FSID/devinfo/devid/ */
+	struct kobject devid_kobj;
 };
 
 /*
@@ -255,7 +257,7 @@ struct btrfs_fs_devices {
 	struct btrfs_fs_info *fs_info;
 	/* sysfs kobjects */
 	struct kobject fsid_kobj;
-	struct kobject *device_dir_kobj;
+	struct kobject *devices_kobj;
 	struct completion kobj_unregister;
 };
 
@@ -417,8 +419,6 @@ int btrfs_map_sblock(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 		     struct btrfs_bio **bbio_ret);
 int btrfs_get_io_geometry(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 		u64 logical, u64 len, struct btrfs_io_geometry *io_geom);
-int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
-		     u64 physical, u64 **logical, int *naddrs, int *stripe_len);
 int btrfs_read_sys_array(struct btrfs_fs_info *fs_info);
 int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info);
 int btrfs_alloc_chunk(struct btrfs_trans_handle *trans, u64 type);