1 files changed, 150 insertions, 76 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 21f34ad0d411..07b5e6f7df67 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -31,10 +31,10 @@
 #include <linux/uuid.h>
 #include <linux/semaphore.h>
 #include <linux/error-injection.h>
+#include <linux/crc32c.h>
 #include <asm/unaligned.h>
 #include "ctree.h"
 #include "disk-io.h"
-#include "hash.h"
 #include "transaction.h"
 #include "btrfs_inode.h"
 #include "volumes.h"
@@ -110,7 +110,7 @@ int __init btrfs_end_io_wq_init(void)
 	return 0;
 }
 
-void btrfs_end_io_wq_exit(void)
+void __cold btrfs_end_io_wq_exit(void)
 {
 	kmem_cache_destroy(btrfs_end_io_wq_cache);
 }
@@ -124,8 +124,8 @@ struct async_submit_bio {
 	void *private_data;
 	struct btrfs_fs_info *fs_info;
 	struct bio *bio;
-	extent_submit_bio_hook_t *submit_bio_start;
-	extent_submit_bio_hook_t *submit_bio_done;
+	extent_submit_bio_start_t *submit_bio_start;
+	extent_submit_bio_done_t *submit_bio_done;
 	int mirror_num;
 	unsigned long bio_flags;
 	/*
@@ -270,7 +270,7 @@ out:
 
 u32 btrfs_csum_data(const char *data, u32 seed, size_t len)
 {
-	return btrfs_crc32c(seed, data, len);
+	return crc32c(seed, data, len);
 }
 
 void btrfs_csum_final(u32 crc, u8 *result)
@@ -403,8 +403,7 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
 
 	if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
 		u32 crc = ~(u32)0;
-		const int csum_size = sizeof(crc);
-		char result[csum_size];
+		char result[sizeof(crc)];
 
 		/*
 		 * The super_block structure does not span the whole
@@ -415,7 +414,7 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
 				crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
 		btrfs_csum_final(crc, result);
 
-		if (memcmp(raw_disk_sb, result, csum_size))
+		if (memcmp(raw_disk_sb, result, sizeof(result)))
 			ret = 1;
 	}
 
@@ -428,13 +427,59 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
 	return ret;
 }
 
+static int verify_level_key(struct btrfs_fs_info *fs_info,
+			    struct extent_buffer *eb, int level,
+			    struct btrfs_key *first_key)
+{
+	int found_level;
+	struct btrfs_key found_key;
+	int ret;
+
+	found_level = btrfs_header_level(eb);
+	if (found_level != level) {
+#ifdef CONFIG_BTRFS_DEBUG
+		WARN_ON(1);
+		btrfs_err(fs_info,
+"tree level mismatch detected, bytenr=%llu level expected=%u has=%u",
+			  eb->start, level, found_level);
+#endif
+		return -EIO;
+	}
+
+	if (!first_key)
+		return 0;
+
+	if (found_level)
+		btrfs_node_key_to_cpu(eb, &found_key, 0);
+	else
+		btrfs_item_key_to_cpu(eb, &found_key, 0);
+	ret = btrfs_comp_cpu_keys(first_key, &found_key);
+
+#ifdef CONFIG_BTRFS_DEBUG
+	if (ret) {
+		WARN_ON(1);
+		btrfs_err(fs_info,
+"tree first key mismatch detected, bytenr=%llu key expected=(%llu, %u, %llu) has=(%llu, %u, %llu)",
+			  eb->start, first_key->objectid, first_key->type,
+			  first_key->offset, found_key.objectid,
+			  found_key.type, found_key.offset);
+	}
+#endif
+	return ret;
+}
+
 /*
  * helper to read a given tree block, doing retries as required when
  * the checksums don't match and we have alternate mirrors to try.
+ *
+ * @parent_transid:	expected transid, skip check if 0
+ * @level:		expected level, mandatory check
+ * @first_key:		expected key of first slot, skip check if NULL
  */
 static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info,
 					  struct extent_buffer *eb,
-					  u64 parent_transid)
+					  u64 parent_transid, int level,
+					  struct btrfs_key *first_key)
 {
 	struct extent_io_tree *io_tree;
 	int failed = 0;
@@ -449,11 +494,14 @@ static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info,
 		ret = read_extent_buffer_pages(io_tree, eb, WAIT_COMPLETE,
 					       mirror_num);
 		if (!ret) {
-			if (!verify_parent_transid(io_tree, eb,
+			if (verify_parent_transid(io_tree, eb,
 						   parent_transid, 0))
-				break;
-			else
 				ret = -EIO;
+			else if (verify_level_key(fs_info, eb, level,
+						  first_key))
+				ret = -EUCLEAN;
+			else
+				break;
 		}
 
 		/*
@@ -461,7 +509,8 @@ static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info,
 		 * there is no reason to read the other copies, they won't be
 		 * any less wrong.
 		 */
-		if (test_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags))
+		if (test_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags) ||
+		    ret == -EUCLEAN)
 			break;
 
 		num_copies = btrfs_num_copies(fs_info,
@@ -602,12 +651,12 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 	 * that we don't try and read the other copies of this block, just
 	 * return -EIO.
 	 */
-	if (found_level == 0 && btrfs_check_leaf_full(root, eb)) {
+	if (found_level == 0 && btrfs_check_leaf_full(fs_info, eb)) {
 		set_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
 		ret = -EIO;
 	}
 
-	if (found_level > 0 && btrfs_check_node(root, eb))
+	if (found_level > 0 && btrfs_check_node(fs_info, eb))
 		ret = -EIO;
 
 	if (!ret)
@@ -710,14 +759,6 @@ blk_status_t btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
 	return 0;
 }
 
-unsigned long btrfs_async_submit_limit(struct btrfs_fs_info *info)
-{
-	unsigned long limit = min_t(unsigned long,
-				    info->thread_pool_size,
-				    info->fs_devices->open_devices);
-	return 256 * limit;
-}
-
 static void run_one_async_start(struct btrfs_work *work)
 {
 	struct async_submit_bio *async;
@@ -725,7 +766,6 @@ static void run_one_async_start(struct btrfs_work *work)
 
 	async = container_of(work, struct  async_submit_bio, work);
 	ret = async->submit_bio_start(async->private_data, async->bio,
-				      async->mirror_num, async->bio_flags,
 				      async->bio_offset);
 	if (ret)
 		async->status = ret;
@@ -744,8 +784,7 @@ static void run_one_async_done(struct btrfs_work *work)
 		return;
 	}
 
-	async->submit_bio_done(async->private_data, async->bio, async->mirror_num,
-			       async->bio_flags, async->bio_offset);
+	async->submit_bio_done(async->private_data, async->bio, async->mirror_num);
 }
 
 static void run_one_async_free(struct btrfs_work *work)
@@ -759,8 +798,8 @@ static void run_one_async_free(struct btrfs_work *work)
 blk_status_t btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
 				 int mirror_num, unsigned long bio_flags,
 				 u64 bio_offset, void *private_data,
-				 extent_submit_bio_hook_t *submit_bio_start,
-				 extent_submit_bio_hook_t *submit_bio_done)
+				 extent_submit_bio_start_t *submit_bio_start,
+				 extent_submit_bio_done_t *submit_bio_done)
 {
 	struct async_submit_bio *async;
 
@@ -807,8 +846,7 @@ static blk_status_t btree_csum_one_bio(struct bio *bio)
 	return errno_to_blk_status(ret);
 }
 
-static blk_status_t __btree_submit_bio_start(void *private_data, struct bio *bio,
-					     int mirror_num, unsigned long bio_flags,
+static blk_status_t btree_submit_bio_start(void *private_data, struct bio *bio,
 					     u64 bio_offset)
 {
 	/*
@@ -818,9 +856,8 @@ static blk_status_t __btree_submit_bio_start(void *private_data, struct bio *bio
 	return btree_csum_one_bio(bio);
 }
 
-static blk_status_t __btree_submit_bio_done(void *private_data, struct bio *bio,
-					    int mirror_num, unsigned long bio_flags,
-					    u64 bio_offset)
+static blk_status_t btree_submit_bio_done(void *private_data, struct bio *bio,
+					    int mirror_num)
 {
 	struct inode *inode = private_data;
 	blk_status_t ret;
@@ -879,8 +916,8 @@ static blk_status_t btree_submit_bio_hook(void *private_data, struct bio *bio,
 		 */
 		ret = btrfs_wq_submit_bio(fs_info, bio, mirror_num, 0,
 					  bio_offset, private_data,
-					  __btree_submit_bio_start,
-					  __btree_submit_bio_done);
+					  btree_submit_bio_start,
+					  btree_submit_bio_done);
 	}
 
 	if (ret)
@@ -1062,8 +1099,17 @@ void btrfs_wait_tree_block_writeback(struct extent_buffer *buf)
 			        buf->start, buf->start + buf->len - 1);
 }
 
+/*
+ * Read tree block at logical address @bytenr and do variant basic but critical
+ * verification.
+ *
+ * @parent_transid:	expected transid of this tree block, skip check if 0
+ * @level:		expected level, mandatory check
+ * @first_key:		expected key in slot 0, skip check if NULL
+ */
 struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
-				      u64 parent_transid)
+				      u64 parent_transid, int level,
+				      struct btrfs_key *first_key)
 {
 	struct extent_buffer *buf = NULL;
 	int ret;
@@ -1072,7 +1118,8 @@ struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
 	if (IS_ERR(buf))
 		return buf;
 
-	ret = btree_read_extent_buffer_pages(fs_info, buf, parent_transid);
+	ret = btree_read_extent_buffer_pages(fs_info, buf, parent_transid,
+					     level, first_key);
 	if (ret) {
 		free_extent_buffer(buf);
 		return ERR_PTR(ret);
@@ -1108,7 +1155,7 @@ static struct btrfs_subvolume_writers *btrfs_alloc_subvolume_writers(void)
 	if (!writers)
 		return ERR_PTR(-ENOMEM);
 
-	ret = percpu_counter_init(&writers->counter, 0, GFP_KERNEL);
+	ret = percpu_counter_init(&writers->counter, 0, GFP_NOFS);
 	if (ret < 0) {
 		kfree(writers);
 		return ERR_PTR(ret);
@@ -1160,6 +1207,7 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
 	spin_lock_init(&root->accounting_lock);
 	spin_lock_init(&root->log_extents_lock[0]);
 	spin_lock_init(&root->log_extents_lock[1]);
+	spin_lock_init(&root->qgroup_meta_rsv_lock);
 	mutex_init(&root->objectid_mutex);
 	mutex_init(&root->log_mutex);
 	mutex_init(&root->ordered_extent_mutex);
@@ -1176,7 +1224,6 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
 	atomic_set(&root->orphan_inodes, 0);
 	refcount_set(&root->refs, 1);
 	atomic_set(&root->will_be_snapshotted, 0);
-	atomic64_set(&root->qgroup_meta_rsv, 0);
 	root->log_transid = 0;
 	root->log_transid_committed = -1;
 	root->last_log_commit = 0;
@@ -1401,6 +1448,7 @@ static struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
 	struct btrfs_path *path;
 	u64 generation;
 	int ret;
+	int level;
 
 	path = btrfs_alloc_path();
 	if (!path)
@@ -1423,9 +1471,10 @@ static struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
 	}
 
 	generation = btrfs_root_generation(&root->root_item);
+	level = btrfs_root_level(&root->root_item);
 	root->node = read_tree_block(fs_info,
 				     btrfs_root_bytenr(&root->root_item),
-				     generation);
+				     generation, level, NULL);
 	if (IS_ERR(root->node)) {
 		ret = PTR_ERR(root->node);
 		goto find_fail;
@@ -1808,12 +1857,10 @@ sleep:
 		if (unlikely(test_bit(BTRFS_FS_STATE_ERROR,
 				      &fs_info->fs_state)))
 			btrfs_cleanup_transaction(fs_info);
-		set_current_state(TASK_INTERRUPTIBLE);
 		if (!kthread_should_stop() &&
 				(!btrfs_transaction_blocked(fs_info) ||
 				 cannot_commit))
-			schedule_timeout(delay);
-		__set_current_state(TASK_RUNNING);
+			schedule_timeout_interruptible(delay);
 	} while (!kthread_should_stop());
 	return 0;
 }
@@ -2183,7 +2230,7 @@ static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info)
 static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
 		struct btrfs_fs_devices *fs_devices)
 {
-	int max_active = fs_info->thread_pool_size;
+	u32 max_active = fs_info->thread_pool_size;
 	unsigned int flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_UNBOUND;
 
 	fs_info->workers =
@@ -2276,6 +2323,7 @@ static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
 	struct btrfs_root *log_tree_root;
 	struct btrfs_super_block *disk_super = fs_info->super_copy;
 	u64 bytenr = btrfs_super_log_root(disk_super);
+	int level = btrfs_super_log_root_level(disk_super);
 
 	if (fs_devices->rw_devices == 0) {
 		btrfs_warn(fs_info, "log replay required on RO media");
@@ -2289,7 +2337,8 @@ static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
 	__setup_root(log_tree_root, fs_info, BTRFS_TREE_LOG_OBJECTID);
 
 	log_tree_root->node = read_tree_block(fs_info, bytenr,
-					      fs_info->generation + 1);
+					      fs_info->generation + 1,
+					      level, NULL);
 	if (IS_ERR(log_tree_root->node)) {
 		btrfs_warn(fs_info, "failed to read log tree");
 		ret = PTR_ERR(log_tree_root->node);
@@ -2334,23 +2383,29 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 	location.offset = 0;
 
 	root = btrfs_read_tree_root(tree_root, &location);
-	if (IS_ERR(root))
-		return PTR_ERR(root);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto out;
+	}
 	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
 	fs_info->extent_root = root;
 
 	location.objectid = BTRFS_DEV_TREE_OBJECTID;
 	root = btrfs_read_tree_root(tree_root, &location);
-	if (IS_ERR(root))
-		return PTR_ERR(root);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto out;
+	}
 	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
 	fs_info->dev_root = root;
 	btrfs_init_devices_late(fs_info);
 
 	location.objectid = BTRFS_CSUM_TREE_OBJECTID;
 	root = btrfs_read_tree_root(tree_root, &location);
-	if (IS_ERR(root))
-		return PTR_ERR(root);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto out;
+	}
 	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
 	fs_info->csum_root = root;
 
@@ -2367,7 +2422,7 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 	if (IS_ERR(root)) {
 		ret = PTR_ERR(root);
 		if (ret != -ENOENT)
-			return ret;
+			goto out;
 	} else {
 		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
 		fs_info->uuid_root = root;
@@ -2376,13 +2431,19 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 	if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
 		location.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID;
 		root = btrfs_read_tree_root(tree_root, &location);
-		if (IS_ERR(root))
-			return PTR_ERR(root);
+		if (IS_ERR(root)) {
+			ret = PTR_ERR(root);
+			goto out;
+		}
 		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
 		fs_info->free_space_root = root;
 	}
 
 	return 0;
+out:
+	btrfs_warn(fs_info, "failed to read root (objectid=%llu): %d",
+		   location.objectid, ret);
+	return ret;
 }
 
 int open_ctree(struct super_block *sb,
@@ -2404,8 +2465,8 @@ int open_ctree(struct super_block *sb,
 	int err = -EINVAL;
 	int num_backups_tried = 0;
 	int backup_index = 0;
-	int max_active;
 	int clear_free_space_tree = 0;
+	int level;
 
 	tree_root = fs_info->tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
 	chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
@@ -2447,6 +2508,8 @@ int open_ctree(struct super_block *sb,
 	INIT_LIST_HEAD(&fs_info->delayed_iputs);
 	INIT_LIST_HEAD(&fs_info->delalloc_roots);
 	INIT_LIST_HEAD(&fs_info->caching_block_groups);
+	INIT_LIST_HEAD(&fs_info->pending_raid_kobjs);
+	spin_lock_init(&fs_info->pending_raid_kobjs_lock);
 	spin_lock_init(&fs_info->delalloc_root_lock);
 	spin_lock_init(&fs_info->trans_lock);
 	spin_lock_init(&fs_info->fs_roots_radix_lock);
@@ -2713,8 +2776,6 @@ int open_ctree(struct super_block *sb,
 		goto fail_alloc;
 	}
 
-	max_active = fs_info->thread_pool_size;
-
 	ret = btrfs_init_workqueues(fs_info, fs_devices);
 	if (ret) {
 		err = ret;
@@ -2741,12 +2802,13 @@ int open_ctree(struct super_block *sb,
 	}
 
 	generation = btrfs_super_chunk_root_generation(disk_super);
+	level = btrfs_super_chunk_root_level(disk_super);
 
 	__setup_root(chunk_root, fs_info, BTRFS_CHUNK_TREE_OBJECTID);
 
 	chunk_root->node = read_tree_block(fs_info,
 					   btrfs_super_chunk_root(disk_super),
-					   generation);
+					   generation, level, NULL);
 	if (IS_ERR(chunk_root->node) ||
 	    !extent_buffer_uptodate(chunk_root->node)) {
 		btrfs_err(fs_info, "failed to read chunk root");
@@ -2768,10 +2830,10 @@ int open_ctree(struct super_block *sb,
 	}
 
 	/*
-	 * keep the device that is marked to be the target device for the
-	 * dev_replace procedure
+	 * Keep the devid that is marked to be the target device for the
+	 * device replace procedure
 	 */
-	btrfs_close_extra_devices(fs_devices, 0);
+	btrfs_free_extra_devids(fs_devices, 0);
 
 	if (!fs_devices->latest_bdev) {
 		btrfs_err(fs_info, "failed to read devices");
@@ -2780,10 +2842,11 @@ int open_ctree(struct super_block *sb,
 
 retry_root_backup:
 	generation = btrfs_super_generation(disk_super);
+	level = btrfs_super_root_level(disk_super);
 
 	tree_root->node = read_tree_block(fs_info,
 					  btrfs_super_root(disk_super),
-					  generation);
+					  generation, level, NULL);
 	if (IS_ERR(tree_root->node) ||
 	    !extent_buffer_uptodate(tree_root->node)) {
 		btrfs_warn(fs_info, "failed to read tree root");
@@ -2834,7 +2897,7 @@ retry_root_backup:
 		goto fail_block_groups;
 	}
 
-	btrfs_close_extra_devices(fs_devices, 1);
+	btrfs_free_extra_devids(fs_devices, 1);
 
 	ret = btrfs_sysfs_add_fsid(fs_devices, NULL);
 	if (ret) {
@@ -2953,6 +3016,7 @@ retry_root_backup:
 	fs_info->fs_root = btrfs_read_fs_root_no_name(fs_info, &location);
 	if (IS_ERR(fs_info->fs_root)) {
 		err = PTR_ERR(fs_info->fs_root);
+		btrfs_warn(fs_info, "failed to read fs tree: %d", err);
 		goto fail_qgroup;
 	}
 
@@ -3290,6 +3354,7 @@ static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
 	struct buffer_head *bh;
 	int i;
 	int errors = 0;
+	bool primary_failed = false;
 	u64 bytenr;
 
 	if (max_mirrors == 0)
@@ -3306,11 +3371,16 @@ static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
 				      BTRFS_SUPER_INFO_SIZE);
 		if (!bh) {
 			errors++;
+			if (i == 0)
+				primary_failed = true;
 			continue;
 		}
 		wait_on_buffer(bh);
-		if (!buffer_uptodate(bh))
+		if (!buffer_uptodate(bh)) {
 			errors++;
+			if (i == 0)
+				primary_failed = true;
+		}
 
 		/* drop our reference */
 		brelse(bh);
@@ -3319,6 +3389,13 @@ static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
 		brelse(bh);
 	}
 
+	/* log error, force error return */
+	if (primary_failed) {
+		btrfs_err(device->fs_info, "error writing primary super block to device %llu",
+			  device->devid);
+		return -1;
+	}
+
 	return errors < i ? 0 : -1;
 }
 
@@ -3851,7 +3928,7 @@ void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
 	 * So here we should only check item pointers, not item data.
 	 */
 	if (btrfs_header_level(buf) == 0 &&
-	    btrfs_check_leaf_relaxed(root, buf)) {
+	    btrfs_check_leaf_relaxed(fs_info, buf)) {
 		btrfs_print_leaf(buf);
 		ASSERT(0);
 	}
@@ -3890,12 +3967,14 @@ void btrfs_btree_balance_dirty_nodelay(struct btrfs_fs_info *fs_info)
 	__btrfs_btree_balance_dirty(fs_info, 0);
 }
 
-int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid)
+int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid, int level,
+		      struct btrfs_key *first_key)
 {
 	struct btrfs_root *root = BTRFS_I(buf->pages[0]->mapping->host)->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 
-	return btree_read_extent_buffer_pages(fs_info, buf, parent_transid);
+	return btree_read_extent_buffer_pages(fs_info, buf, parent_transid,
+					      level, first_key);
 }
 
 static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
@@ -4314,11 +4393,6 @@ void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans,
 		cache = list_first_entry(&cur_trans->dirty_bgs,
 					 struct btrfs_block_group_cache,
 					 dirty_list);
-		if (!cache) {
-			btrfs_err(fs_info, "orphan block group dirty_bgs list");
-			spin_unlock(&cur_trans->dirty_bgs_lock);
-			return;
-		}
 
 		if (!list_empty(&cache->io_list)) {
 			spin_unlock(&cur_trans->dirty_bgs_lock);
@@ -4338,14 +4412,14 @@ void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans,
 	}
 	spin_unlock(&cur_trans->dirty_bgs_lock);
 
+	/*
+	 * Refer to the definition of io_bgs member for details why it's safe
+	 * to use it without any locking
+	 */
 	while (!list_empty(&cur_trans->io_bgs)) {
 		cache = list_first_entry(&cur_trans->io_bgs,
 					 struct btrfs_block_group_cache,
 					 io_list);
-		if (!cache) {
-			btrfs_err(fs_info, "orphan block group on io_bgs list");
-			return;
-		}
 
 		list_del_init(&cache->io_list);
 		spin_lock(&cache->lock);