1 files changed, 287 insertions, 167 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 1c3a1189c0bd..d1f1da6820fb 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -10,6 +10,7 @@
 #include <linux/pagemap.h>
 #include <linux/blkdev.h>
 #include <linux/uuid.h>
+#include <linux/timekeeping.h>
 #include "misc.h"
 #include "ctree.h"
 #include "disk-io.h"
@@ -160,9 +161,18 @@ 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;
-	struct btrfs_caching_control *caching_ctl, *next;
+
+	/*
+	 * At this point no one can be using this transaction to modify any tree
+	 * and no one can start another transaction to modify any tree either.
+	 */
+	ASSERT(cur_trans->state == TRANS_STATE_COMMIT_DOING);
 
 	down_write(&fs_info->commit_root_sem);
+
+	if (test_bit(BTRFS_FS_RELOC_RUNNING, &fs_info->flags))
+		fs_info->last_reloc_trans = trans->transid;
+
 	list_for_each_entry_safe(root, tmp, &cur_trans->switch_commits,
 				 dirty_list) {
 		list_del_init(&root->dirty_list);
@@ -185,46 +195,6 @@ static noinline void switch_commit_roots(struct btrfs_trans_handle *trans)
 	}
 	spin_unlock(&cur_trans->dropped_roots_lock);
 
-	/*
-	 * We have to update the last_byte_to_unpin under the commit_root_sem,
-	 * at the same time we swap out the commit roots.
-	 *
-	 * This is because we must have a real view of the last spot the caching
-	 * kthreads were while caching.  Consider the following views of the
-	 * extent tree for a block group
-	 *
-	 * commit root
-	 * +----+----+----+----+----+----+----+
-	 * |\\\\|    |\\\\|\\\\|    |\\\\|\\\\|
-	 * +----+----+----+----+----+----+----+
-	 * 0    1    2    3    4    5    6    7
-	 *
-	 * new commit root
-	 * +----+----+----+----+----+----+----+
-	 * |    |    |    |\\\\|    |    |\\\\|
-	 * +----+----+----+----+----+----+----+
-	 * 0    1    2    3    4    5    6    7
-	 *
-	 * If the cache_ctl->progress was at 3, then we are only allowed to
-	 * unpin [0,1) and [2,3], because the caching thread has already
-	 * processed those extents.  We are not allowed to unpin [5,6), because
-	 * the caching thread will re-start it's search from 3, and thus find
-	 * the hole from [4,6) to add to the free space cache.
-	 */
-	spin_lock(&fs_info->block_group_cache_lock);
-	list_for_each_entry_safe(caching_ctl, next,
-				 &fs_info->caching_block_groups, list) {
-		struct btrfs_block_group *cache = caching_ctl->block_group;
-
-		if (btrfs_block_group_done(cache)) {
-			cache->last_byte_to_unpin = (u64)-1;
-			list_del_init(&caching_ctl->list);
-			btrfs_put_caching_control(caching_ctl);
-		} else {
-			cache->last_byte_to_unpin = caching_ctl->progress;
-		}
-	}
-	spin_unlock(&fs_info->block_group_cache_lock);
 	up_write(&fs_info->commit_root_sem);
 }
 
@@ -302,6 +272,8 @@ loop:
 		atomic_inc(&cur_trans->num_writers);
 		extwriter_counter_inc(cur_trans, type);
 		spin_unlock(&fs_info->trans_lock);
+		btrfs_lockdep_acquire(fs_info, btrfs_trans_num_writers);
+		btrfs_lockdep_acquire(fs_info, btrfs_trans_num_extwriters);
 		return 0;
 	}
 	spin_unlock(&fs_info->trans_lock);
@@ -323,16 +295,23 @@ loop:
 	if (!cur_trans)
 		return -ENOMEM;
 
+	btrfs_lockdep_acquire(fs_info, btrfs_trans_num_writers);
+	btrfs_lockdep_acquire(fs_info, btrfs_trans_num_extwriters);
+
 	spin_lock(&fs_info->trans_lock);
 	if (fs_info->running_transaction) {
 		/*
 		 * someone started a transaction after we unlocked.  Make sure
 		 * to redo the checks above
 		 */
+		btrfs_lockdep_release(fs_info, btrfs_trans_num_extwriters);
+		btrfs_lockdep_release(fs_info, btrfs_trans_num_writers);
 		kfree(cur_trans);
 		goto loop;
 	} else if (BTRFS_FS_ERROR(fs_info)) {
 		spin_unlock(&fs_info->trans_lock);
+		btrfs_lockdep_release(fs_info, btrfs_trans_num_extwriters);
+		btrfs_lockdep_release(fs_info, btrfs_trans_num_writers);
 		kfree(cur_trans);
 		return -EROFS;
 	}
@@ -386,7 +365,7 @@ loop:
 	spin_lock_init(&cur_trans->releasing_ebs_lock);
 	list_add_tail(&cur_trans->list, &fs_info->trans_list);
 	extent_io_tree_init(fs_info, &cur_trans->dirty_pages,
-			IO_TREE_TRANS_DIRTY_PAGES, fs_info->btree_inode);
+			IO_TREE_TRANS_DIRTY_PAGES, NULL);
 	extent_io_tree_init(fs_info, &cur_trans->pinned_extents,
 			IO_TREE_FS_PINNED_EXTENTS, NULL);
 	fs_info->generation++;
@@ -413,7 +392,6 @@ static int record_root_in_trans(struct btrfs_trans_handle *trans,
 
 	if ((test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&
 	    root->last_trans < trans->transid) || force) {
-		WARN_ON(root == fs_info->extent_root);
 		WARN_ON(!force && root->commit_root != root->node);
 
 		/*
@@ -531,6 +509,7 @@ static void wait_current_trans(struct btrfs_fs_info *fs_info)
 		refcount_inc(&cur_trans->use_count);
 		spin_unlock(&fs_info->trans_lock);
 
+		btrfs_might_wait_for_state(fs_info, BTRFS_LOCKDEP_TRANS_UNBLOCKED);
 		wait_event(fs_info->transaction_wait,
 			   cur_trans->state >= TRANS_STATE_UNBLOCKED ||
 			   TRANS_ABORTED(cur_trans));
@@ -615,7 +594,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items,
 		 */
 		num_bytes = btrfs_calc_insert_metadata_size(fs_info, num_items);
 		if (flush == BTRFS_RESERVE_FLUSH_ALL &&
-		    delayed_refs_rsv->full == 0) {
+		    btrfs_block_rsv_full(delayed_refs_rsv) == 0) {
 			delayed_refs_bytes = num_bytes;
 			num_bytes <<= 1;
 		}
@@ -628,7 +607,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items,
 			reloc_reserved = true;
 		}
 
-		ret = btrfs_block_rsv_add(root, rsv, num_bytes, flush);
+		ret = btrfs_block_rsv_add(fs_info, rsv, num_bytes, flush);
 		if (ret)
 			goto reserve_fail;
 		if (delayed_refs_bytes) {
@@ -640,7 +619,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items,
 		if (rsv->space_info->force_alloc)
 			do_chunk_alloc = true;
 	} else if (num_items == 0 && flush == BTRFS_RESERVE_FLUSH_ALL &&
-		   !delayed_refs_rsv->full) {
+		   !btrfs_block_rsv_full(delayed_refs_rsv)) {
 		/*
 		 * Some people call with btrfs_start_transaction(root, 0)
 		 * because they can be throttled, but have some other mechanism
@@ -692,7 +671,6 @@ again:
 
 	h->transid = cur_trans->transid;
 	h->transaction = cur_trans;
-	h->root = root;
 	refcount_set(&h->use_count, 1);
 	h->fs_info = root->fs_info;
 
@@ -846,7 +824,46 @@ btrfs_attach_transaction_barrier(struct btrfs_root *root)
 static noinline void wait_for_commit(struct btrfs_transaction *commit,
 				     const enum btrfs_trans_state min_state)
 {
-	wait_event(commit->commit_wait, commit->state >= min_state);
+	struct btrfs_fs_info *fs_info = commit->fs_info;
+	u64 transid = commit->transid;
+	bool put = false;
+
+	/*
+	 * At the moment this function is called with min_state either being
+	 * TRANS_STATE_COMPLETED or TRANS_STATE_SUPER_COMMITTED.
+	 */
+	if (min_state == TRANS_STATE_COMPLETED)
+		btrfs_might_wait_for_state(fs_info, BTRFS_LOCKDEP_TRANS_COMPLETED);
+	else
+		btrfs_might_wait_for_state(fs_info, BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED);
+
+	while (1) {
+		wait_event(commit->commit_wait, commit->state >= min_state);
+		if (put)
+			btrfs_put_transaction(commit);
+
+		if (min_state < TRANS_STATE_COMPLETED)
+			break;
+
+		/*
+		 * A transaction isn't really completed until all of the
+		 * previous transactions are completed, but with fsync we can
+		 * end up with SUPER_COMMITTED transactions before a COMPLETED
+		 * transaction. Wait for those.
+		 */
+
+		spin_lock(&fs_info->trans_lock);
+		commit = list_first_entry_or_null(&fs_info->trans_list,
+						  struct btrfs_transaction,
+						  list);
+		if (!commit || commit->transid > transid) {
+			spin_unlock(&fs_info->trans_lock);
+			break;
+		}
+		refcount_inc(&commit->use_count);
+		put = true;
+		spin_unlock(&fs_info->trans_lock);
+	}
 }
 
 int btrfs_wait_for_commit(struct btrfs_fs_info *fs_info, u64 transid)
@@ -983,6 +1000,10 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 	extwriter_counter_dec(cur_trans, trans->type);
 
 	cond_wake_up(&cur_trans->writer_wait);
+
+	btrfs_lockdep_release(info, btrfs_trans_num_extwriters);
+	btrfs_lockdep_release(info, btrfs_trans_num_writers);
+
 	btrfs_put_transaction(cur_trans);
 
 	if (current->journal_info == trans)
@@ -1095,7 +1116,7 @@ static int __btrfs_wait_marked_extents(struct btrfs_fs_info *fs_info,
 		 * it's safe to do it (through extent_io_tree_release()).
 		 */
 		err = clear_extent_bit(dirty_pages, start, end,
-				       EXTENT_NEED_WAIT, 0, 0, &cached_state);
+				       EXTENT_NEED_WAIT, &cached_state);
 		if (err == -ENOMEM)
 			err = 0;
 		if (!err)
@@ -1236,6 +1257,12 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans)
 	struct extent_buffer *eb;
 	int ret;
 
+	/*
+	 * At this point no one can be using this transaction to modify any tree
+	 * and no one can start another transaction to modify any tree either.
+	 */
+	ASSERT(trans->transaction->state == TRANS_STATE_COMMIT_DOING);
+
 	eb = btrfs_lock_root_node(fs_info->tree_root);
 	ret = btrfs_cow_block(trans, fs_info->tree_root, eb, NULL,
 			      0, &eb, BTRFS_NESTING_COW);
@@ -1267,9 +1294,8 @@ again:
 		root = list_entry(next, struct btrfs_root, dirty_list);
 		clear_bit(BTRFS_ROOT_DIRTY, &root->state);
 
-		if (root != fs_info->extent_root)
-			list_add_tail(&root->dirty_list,
-				      &trans->transaction->switch_commits);
+		list_add_tail(&root->dirty_list,
+			      &trans->transaction->switch_commits);
 		ret = update_cowonly_root(trans, root);
 		if (ret)
 			return ret;
@@ -1299,9 +1325,6 @@ again:
 	if (!list_empty(&fs_info->dirty_cowonly_roots))
 		goto again;
 
-	list_add_tail(&fs_info->extent_root->dirty_list,
-		      &trans->transaction->switch_commits);
-
 	/* Update dev-replace pointer once everything is committed */
 	fs_info->dev_replace.committed_cursor_left =
 		fs_info->dev_replace.cursor_left_last_write_of_item;
@@ -1310,6 +1333,32 @@ again:
 }
 
 /*
+ * If we had a pending drop we need to see if there are any others left in our
+ * dead roots list, and if not clear our bit and wake any waiters.
+ */
+void btrfs_maybe_wake_unfinished_drop(struct btrfs_fs_info *fs_info)
+{
+	/*
+	 * We put the drop in progress roots at the front of the list, so if the
+	 * first entry doesn't have UNFINISHED_DROP set we can wake everybody
+	 * up.
+	 */
+	spin_lock(&fs_info->trans_lock);
+	if (!list_empty(&fs_info->dead_roots)) {
+		struct btrfs_root *root = list_first_entry(&fs_info->dead_roots,
+							   struct btrfs_root,
+							   root_list);
+		if (test_bit(BTRFS_ROOT_UNFINISHED_DROP, &root->state)) {
+			spin_unlock(&fs_info->trans_lock);
+			return;
+		}
+	}
+	spin_unlock(&fs_info->trans_lock);
+
+	btrfs_wake_unfinished_drop(fs_info);
+}
+
+/*
  * dead roots are old snapshots that need to be deleted.  This allocates
  * a dirty root struct and adds it into the list of dead roots that need to
  * be deleted
@@ -1321,13 +1370,19 @@ void btrfs_add_dead_root(struct btrfs_root *root)
 	spin_lock(&fs_info->trans_lock);
 	if (list_empty(&root->root_list)) {
 		btrfs_grab_root(root);
-		list_add_tail(&root->root_list, &fs_info->dead_roots);
+
+		/* We want to process the partially complete drops first. */
+		if (test_bit(BTRFS_ROOT_UNFINISHED_DROP, &root->state))
+			list_add(&root->root_list, &fs_info->dead_roots);
+		else
+			list_add_tail(&root->root_list, &fs_info->dead_roots);
 	}
 	spin_unlock(&fs_info->trans_lock);
 }
 
 /*
- * update all the cowonly tree roots on disk
+ * Update each subvolume root and its relocation root, if it exists, in the tree
+ * of tree roots. Also free log roots if they exist.
  */
 static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
 {
@@ -1336,6 +1391,12 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
 	int i;
 	int ret;
 
+	/*
+	 * At this point no one can be using this transaction to modify any tree
+	 * and no one can start another transaction to modify any tree either.
+	 */
+	ASSERT(trans->transaction->state == TRANS_STATE_COMMIT_DOING);
+
 	spin_lock(&fs_info->fs_roots_radix_lock);
 	while (1) {
 		ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
@@ -1348,6 +1409,14 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
 			struct btrfs_root *root = gang[i];
 			int ret2;
 
+			/*
+			 * At this point we can neither have tasks logging inodes
+			 * from a root nor trying to commit a log tree.
+			 */
+			ASSERT(atomic_read(&root->log_writers) == 0);
+			ASSERT(atomic_read(&root->log_commit[0]) == 0);
+			ASSERT(atomic_read(&root->log_commit[1]) == 0);
+
 			radix_tree_tag_clear(&fs_info->fs_roots_radix,
 					(unsigned long)root->root_key.objectid,
 					BTRFS_ROOT_TRANS_TAG);
@@ -1472,12 +1541,6 @@ static int qgroup_account_snapshot(struct btrfs_trans_handle *trans,
 		return ret;
 	}
 
-	/*
-	 * We are going to commit transaction, see btrfs_commit_transaction()
-	 * comment for reason locking tree_log_mutex
-	 */
-	mutex_lock(&fs_info->tree_log_mutex);
-
 	ret = commit_fs_roots(trans);
 	if (ret)
 		goto out;
@@ -1513,8 +1576,6 @@ static int qgroup_account_snapshot(struct btrfs_trans_handle *trans,
 			"Error while writing out transaction for qgroup");
 
 out:
-	mutex_unlock(&fs_info->tree_log_mutex);
-
 	/*
 	 * Force parent root to be updated, as we recorded it before so its
 	 * last_trans == cur_transid.
@@ -1578,7 +1639,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	btrfs_reloc_pre_snapshot(pending, &to_reserve);
 
 	if (to_reserve > 0) {
-		pending->error = btrfs_block_rsv_add(root,
+		pending->error = btrfs_block_rsv_add(fs_info,
 						     &pending->block_rsv,
 						     to_reserve,
 						     BTRFS_RESERVE_NO_FLUSH);
@@ -1753,8 +1814,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 
 	btrfs_i_size_write(BTRFS_I(parent_inode), parent_inode->i_size +
 					 dentry->d_name.len * 2);
-	parent_inode->i_mtime = parent_inode->i_ctime =
-		current_time(parent_inode);
+	parent_inode->i_mtime = current_time(parent_inode);
+	parent_inode->i_ctime = parent_inode->i_mtime;
 	ret = btrfs_update_inode_fallback(trans, parent_root, BTRFS_I(parent_inode));
 	if (ret) {
 		btrfs_abort_transaction(trans, ret);
@@ -1861,50 +1922,14 @@ int btrfs_transaction_blocked(struct btrfs_fs_info *info)
 	return ret;
 }
 
-/*
- * commit transactions asynchronously. once btrfs_commit_transaction_async
- * returns, any subsequent transaction will not be allowed to join.
- */
-struct btrfs_async_commit {
-	struct btrfs_trans_handle *newtrans;
-	struct work_struct work;
-};
-
-static void do_async_commit(struct work_struct *work)
-{
-	struct btrfs_async_commit *ac =
-		container_of(work, struct btrfs_async_commit, work);
-
-	/*
-	 * We've got freeze protection passed with the transaction.
-	 * Tell lockdep about it.
-	 */
-	if (ac->newtrans->type & __TRANS_FREEZABLE)
-		__sb_writers_acquired(ac->newtrans->fs_info->sb, SB_FREEZE_FS);
-
-	current->journal_info = ac->newtrans;
-
-	btrfs_commit_transaction(ac->newtrans);
-	kfree(ac);
-}
-
-int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans)
+void btrfs_commit_transaction_async(struct btrfs_trans_handle *trans)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_async_commit *ac;
 	struct btrfs_transaction *cur_trans;
 
-	ac = kmalloc(sizeof(*ac), GFP_NOFS);
-	if (!ac)
-		return -ENOMEM;
-
-	INIT_WORK(&ac->work, do_async_commit);
-	ac->newtrans = btrfs_join_transaction(trans->root);
-	if (IS_ERR(ac->newtrans)) {
-		int err = PTR_ERR(ac->newtrans);
-		kfree(ac);
-		return err;
-	}
+	/* Kick the transaction kthread. */
+	set_bit(BTRFS_FS_COMMIT_TRANS, &fs_info->flags);
+	wake_up_process(fs_info->transaction_kthread);
 
 	/* take transaction reference */
 	cur_trans = trans->transaction;
@@ -1913,28 +1938,16 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans)
 	btrfs_end_transaction(trans);
 
 	/*
-	 * Tell lockdep we've released the freeze rwsem, since the
-	 * async commit thread will be the one to unlock it.
-	 */
-	if (ac->newtrans->type & __TRANS_FREEZABLE)
-		__sb_writers_release(fs_info->sb, SB_FREEZE_FS);
-
-	schedule_work(&ac->work);
-	/*
 	 * Wait for the current transaction commit to start and block
 	 * subsequent transaction joins
 	 */
+	btrfs_might_wait_for_state(fs_info, BTRFS_LOCKDEP_TRANS_COMMIT_START);
 	wait_event(fs_info->transaction_blocked_wait,
 		   cur_trans->state >= TRANS_STATE_COMMIT_START ||
 		   TRANS_ABORTED(cur_trans));
-	if (current->journal_info == trans)
-		current->journal_info = NULL;
-
 	btrfs_put_transaction(cur_trans);
-	return 0;
 }
 
-
 static void cleanup_transaction(struct btrfs_trans_handle *trans, int err)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
@@ -1956,6 +1969,12 @@ static void cleanup_transaction(struct btrfs_trans_handle *trans, int err)
 	if (cur_trans == fs_info->running_transaction) {
 		cur_trans->state = TRANS_STATE_COMMIT_DOING;
 		spin_unlock(&fs_info->trans_lock);
+
+		/*
+		 * The thread has already released the lockdep map as reader
+		 * already in btrfs_commit_transaction().
+		 */
+		btrfs_might_wait_for_event(fs_info, btrfs_trans_num_writers);
 		wait_event(cur_trans->writer_wait,
 			   atomic_read(&cur_trans->num_writers) == 1);
 
@@ -1986,7 +2005,7 @@ static void cleanup_transaction(struct btrfs_trans_handle *trans, int err)
 	btrfs_put_transaction(cur_trans);
 	btrfs_put_transaction(cur_trans);
 
-	trace_btrfs_transaction_commit(trans->root);
+	trace_btrfs_transaction_commit(fs_info);
 
 	if (current->journal_info == trans)
 		current->journal_info = NULL;
@@ -2013,16 +2032,24 @@ static void btrfs_cleanup_pending_block_groups(struct btrfs_trans_handle *trans)
 static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
 {
 	/*
-	 * We use writeback_inodes_sb here because if we used
+	 * We use try_to_writeback_inodes_sb() here because if we used
 	 * btrfs_start_delalloc_roots we would deadlock with fs freeze.
 	 * Currently are holding the fs freeze lock, if we do an async flush
 	 * we'll do btrfs_join_transaction() and deadlock because we need to
 	 * wait for the fs freeze lock.  Using the direct flushing we benefit
 	 * from already being in a transaction and our join_transaction doesn't
 	 * have to re-take the fs freeze lock.
+	 *
+	 * Note that try_to_writeback_inodes_sb() will only trigger writeback
+	 * if it can read lock sb->s_umount. It will always be able to lock it,
+	 * except when the filesystem is being unmounted or being frozen, but in
+	 * those cases sync_filesystem() is called, which results in calling
+	 * writeback_inodes_sb() while holding a write lock on sb->s_umount.
+	 * Note that we don't call writeback_inodes_sb() directly, because it
+	 * will emit a warning if sb->s_umount is not locked.
 	 */
 	if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
-		writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
+		try_to_writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
 	return 0;
 }
 
@@ -2032,20 +2059,52 @@ static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
 		btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 }
 
+/*
+ * Add a pending snapshot associated with the given transaction handle to the
+ * respective handle. This must be called after the transaction commit started
+ * and while holding fs_info->trans_lock.
+ * This serves to guarantee a caller of btrfs_commit_transaction() that it can
+ * safely free the pending snapshot pointer in case btrfs_commit_transaction()
+ * returns an error.
+ */
+static void add_pending_snapshot(struct btrfs_trans_handle *trans)
+{
+	struct btrfs_transaction *cur_trans = trans->transaction;
+
+	if (!trans->pending_snapshot)
+		return;
+
+	lockdep_assert_held(&trans->fs_info->trans_lock);
+	ASSERT(cur_trans->state >= TRANS_STATE_COMMIT_START);
+
+	list_add(&trans->pending_snapshot->list, &cur_trans->pending_snapshots);
+}
+
+static void update_commit_stats(struct btrfs_fs_info *fs_info, ktime_t interval)
+{
+	fs_info->commit_stats.commit_count++;
+	fs_info->commit_stats.last_commit_dur = interval;
+	fs_info->commit_stats.max_commit_dur =
+			max_t(u64, fs_info->commit_stats.max_commit_dur, interval);
+	fs_info->commit_stats.total_commit_dur += interval;
+}
+
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
 	struct btrfs_transaction *cur_trans = trans->transaction;
 	struct btrfs_transaction *prev_trans = NULL;
 	int ret;
+	ktime_t start_time;
+	ktime_t interval;
 
 	ASSERT(refcount_read(&trans->use_count) == 1);
+	btrfs_trans_state_lockdep_acquire(fs_info, BTRFS_LOCKDEP_TRANS_COMMIT_START);
 
 	/* Stop the commit early if ->aborted is set */
 	if (TRANS_ABORTED(cur_trans)) {
 		ret = cur_trans->aborted;
-		btrfs_end_transaction(trans);
-		return ret;
+		goto lockdep_trans_commit_start_release;
 	}
 
 	btrfs_trans_release_metadata(trans);
@@ -2062,10 +2121,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 		 * Any running threads may add more while we are here.
 		 */
 		ret = btrfs_run_delayed_refs(trans, 0);
-		if (ret) {
-			btrfs_end_transaction(trans);
-			return ret;
-		}
+		if (ret)
+			goto lockdep_trans_commit_start_release;
 	}
 
 	btrfs_create_pending_block_groups(trans);
@@ -2094,10 +2151,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
 		if (run_it) {
 			ret = btrfs_start_dirty_block_groups(trans);
-			if (ret) {
-				btrfs_end_transaction(trans);
-				return ret;
-			}
+			if (ret)
+				goto lockdep_trans_commit_start_release;
 		}
 	}
 
@@ -2105,11 +2160,16 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
 		enum btrfs_trans_state want_state = TRANS_STATE_COMPLETED;
 
+		add_pending_snapshot(trans);
+
 		spin_unlock(&fs_info->trans_lock);
 		refcount_inc(&cur_trans->use_count);
 
 		if (trans->in_fsync)
 			want_state = TRANS_STATE_SUPER_COMMITTED;
+
+		btrfs_trans_state_lockdep_release(fs_info,
+						  BTRFS_LOCKDEP_TRANS_COMMIT_START);
 		ret = btrfs_end_transaction(trans);
 		wait_for_commit(cur_trans, want_state);
 
@@ -2123,6 +2183,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
 	cur_trans->state = TRANS_STATE_COMMIT_START;
 	wake_up(&fs_info->transaction_blocked_wait);
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_COMMIT_START);
 
 	if (cur_trans->list.prev != &fs_info->trans_list) {
 		enum btrfs_trans_state want_state = TRANS_STATE_COMPLETED;
@@ -2142,7 +2203,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
 			btrfs_put_transaction(prev_trans);
 			if (ret)
-				goto cleanup_transaction;
+				goto lockdep_release;
 		} else {
 			spin_unlock(&fs_info->trans_lock);
 		}
@@ -2156,27 +2217,42 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 		 */
 		if (BTRFS_FS_ERROR(fs_info)) {
 			ret = -EROFS;
-			goto cleanup_transaction;
+			goto lockdep_release;
 		}
 	}
 
+	/*
+	 * Get the time spent on the work done by the commit thread and not
+	 * the time spent waiting on a previous commit
+	 */
+	start_time = ktime_get_ns();
+
 	extwriter_counter_dec(cur_trans, trans->type);
 
 	ret = btrfs_start_delalloc_flush(fs_info);
 	if (ret)
-		goto cleanup_transaction;
+		goto lockdep_release;
 
 	ret = btrfs_run_delayed_items(trans);
 	if (ret)
-		goto cleanup_transaction;
+		goto lockdep_release;
 
+	/*
+	 * The thread has started/joined the transaction thus it holds the
+	 * lockdep map as a reader. It has to release it before acquiring the
+	 * lockdep map as a writer.
+	 */
+	btrfs_lockdep_release(fs_info, btrfs_trans_num_extwriters);
+	btrfs_might_wait_for_event(fs_info, btrfs_trans_num_extwriters);
 	wait_event(cur_trans->writer_wait,
 		   extwriter_counter_read(cur_trans) == 0);
 
 	/* some pending stuffs might be added after the previous flush. */
 	ret = btrfs_run_delayed_items(trans);
-	if (ret)
+	if (ret) {
+		btrfs_lockdep_release(fs_info, btrfs_trans_num_writers);
 		goto cleanup_transaction;
+	}
 
 	btrfs_wait_delalloc_flush(fs_info);
 
@@ -2185,6 +2261,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	 * transaction. Otherwise if this transaction commits before the ordered
 	 * extents complete we lose logged data after a power failure.
 	 */
+	btrfs_might_wait_for_event(fs_info, btrfs_trans_pending_ordered);
 	wait_event(cur_trans->pending_wait,
 		   atomic_read(&cur_trans->pending_ordered) == 0);
 
@@ -2195,13 +2272,40 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	 * COMMIT_DOING so make sure to wait for num_writers to == 1 again.
 	 */
 	spin_lock(&fs_info->trans_lock);
+	add_pending_snapshot(trans);
 	cur_trans->state = TRANS_STATE_COMMIT_DOING;
 	spin_unlock(&fs_info->trans_lock);
+
+	/*
+	 * The thread has started/joined the transaction thus it holds the
+	 * lockdep map as a reader. It has to release it before acquiring the
+	 * lockdep map as a writer.
+	 */
+	btrfs_lockdep_release(fs_info, btrfs_trans_num_writers);
+	btrfs_might_wait_for_event(fs_info, btrfs_trans_num_writers);
 	wait_event(cur_trans->writer_wait,
 		   atomic_read(&cur_trans->num_writers) == 1);
 
+	/*
+	 * Make lockdep happy by acquiring the state locks after
+	 * btrfs_trans_num_writers is released. If we acquired the state locks
+	 * before releasing the btrfs_trans_num_writers lock then lockdep would
+	 * complain because we did not follow the reverse order unlocking rule.
+	 */
+	btrfs_trans_state_lockdep_acquire(fs_info, BTRFS_LOCKDEP_TRANS_COMPLETED);
+	btrfs_trans_state_lockdep_acquire(fs_info, BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED);
+	btrfs_trans_state_lockdep_acquire(fs_info, BTRFS_LOCKDEP_TRANS_UNBLOCKED);
+
+	/*
+	 * We've started the commit, clear the flag in case we were triggered to
+	 * do an async commit but somebody else started before the transaction
+	 * kthread could do the work.
+	 */
+	clear_bit(BTRFS_FS_COMMIT_TRANS, &fs_info->flags);
+
 	if (TRANS_ABORTED(cur_trans)) {
 		ret = cur_trans->aborted;
+		btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_UNBLOCKED);
 		goto scrub_continue;
 	}
 	/*
@@ -2246,24 +2350,9 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
 	WARN_ON(cur_trans != trans->transaction);
 
-	/* btrfs_commit_tree_roots is responsible for getting the
-	 * various roots consistent with each other.  Every pointer
-	 * in the tree of tree roots has to point to the most up to date
-	 * root for every subvolume and other tree.  So, we have to keep
-	 * the tree logging code from jumping in and changing any
-	 * of the trees.
-	 *
-	 * At this point in the commit, there can't be any tree-log
-	 * writers, but a little lower down we drop the trans mutex
-	 * and let new people in.  By holding the tree_log_mutex
-	 * from now until after the super is written, we avoid races
-	 * with the tree-log code.
-	 */
-	mutex_lock(&fs_info->tree_log_mutex);
-
 	ret = commit_fs_roots(trans);
 	if (ret)
-		goto unlock_tree_log;
+		goto unlock_reloc;
 
 	/*
 	 * Since the transaction is done, we can apply the pending changes
@@ -2282,11 +2371,11 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	 */
 	ret = btrfs_qgroup_account_extents(trans);
 	if (ret < 0)
-		goto unlock_tree_log;
+		goto unlock_reloc;
 
 	ret = commit_cowonly_roots(trans);
 	if (ret)
-		goto unlock_tree_log;
+		goto unlock_reloc;
 
 	/*
 	 * The tasks which save the space cache and inode cache may also
@@ -2294,7 +2383,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	 */
 	if (TRANS_ABORTED(cur_trans)) {
 		ret = cur_trans->aborted;
-		goto unlock_tree_log;
+		goto unlock_reloc;
 	}
 
 	cur_trans = fs_info->running_transaction;
@@ -2309,6 +2398,13 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	list_add_tail(&fs_info->chunk_root->dirty_list,
 		      &cur_trans->switch_commits);
 
+	if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
+		btrfs_set_root_node(&fs_info->block_group_root->root_item,
+				    fs_info->block_group_root->node);
+		list_add_tail(&fs_info->block_group_root->dirty_list,
+			      &cur_trans->switch_commits);
+	}
+
 	switch_commit_roots(trans);
 
 	ASSERT(list_empty(&cur_trans->dirty_bgs));
@@ -2327,6 +2423,16 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
 	btrfs_trans_release_chunk_metadata(trans);
 
+	/*
+	 * Before changing the transaction state to TRANS_STATE_UNBLOCKED and
+	 * setting fs_info->running_transaction to NULL, lock tree_log_mutex to
+	 * make sure that before we commit our superblock, no other task can
+	 * start a new transaction and commit a log tree before we commit our
+	 * superblock. Anyone trying to commit a log tree locks this mutex before
+	 * writing its superblock.
+	 */
+	mutex_lock(&fs_info->tree_log_mutex);
+
 	spin_lock(&fs_info->trans_lock);
 	cur_trans->state = TRANS_STATE_UNBLOCKED;
 	fs_info->running_transaction = NULL;
@@ -2334,15 +2440,12 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	mutex_unlock(&fs_info->reloc_mutex);
 
 	wake_up(&fs_info->transaction_wait);
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_UNBLOCKED);
 
 	ret = btrfs_write_and_wait_transaction(trans);
 	if (ret) {
 		btrfs_handle_fs_error(fs_info, ret,
 				      "Error while writing out transaction");
-		/*
-		 * reloc_mutex has been unlocked, tree_log_mutex is still held
-		 * but we can't jump to unlock_tree_log causing double unlock
-		 */
 		mutex_unlock(&fs_info->tree_log_mutex);
 		goto scrub_continue;
 	}
@@ -2369,6 +2472,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	 */
 	cur_trans->state = TRANS_STATE_SUPER_COMMITTED;
 	wake_up(&cur_trans->commit_wait);
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED);
 
 	btrfs_finish_extent_commit(trans);
 
@@ -2382,6 +2486,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	 */
 	cur_trans->state = TRANS_STATE_COMPLETED;
 	wake_up(&cur_trans->commit_wait);
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_COMPLETED);
 
 	spin_lock(&fs_info->trans_lock);
 	list_del_init(&cur_trans->list);
@@ -2393,7 +2498,9 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	if (trans->type & __TRANS_FREEZABLE)
 		sb_end_intwrite(fs_info->sb);
 
-	trace_btrfs_transaction_commit(trans->root);
+	trace_btrfs_transaction_commit(fs_info);
+
+	interval = ktime_get_ns() - start_time;
 
 	btrfs_scrub_continue(fs_info);
 
@@ -2402,13 +2509,16 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
 	kmem_cache_free(btrfs_trans_handle_cachep, trans);
 
+	update_commit_stats(fs_info, interval);
+
 	return ret;
 
-unlock_tree_log:
-	mutex_unlock(&fs_info->tree_log_mutex);
 unlock_reloc:
 	mutex_unlock(&fs_info->reloc_mutex);
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_UNBLOCKED);
 scrub_continue:
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED);
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_COMPLETED);
 	btrfs_scrub_continue(fs_info);
 cleanup_transaction:
 	btrfs_trans_release_metadata(trans);
@@ -2421,6 +2531,16 @@ cleanup_transaction:
 	cleanup_transaction(trans, ret);
 
 	return ret;
+
+lockdep_release:
+	btrfs_lockdep_release(fs_info, btrfs_trans_num_extwriters);
+	btrfs_lockdep_release(fs_info, btrfs_trans_num_writers);
+	goto cleanup_transaction;
+
+lockdep_trans_commit_start_release:
+	btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_COMMIT_START);
+	btrfs_end_transaction(trans);
+	return ret;
 }
 
 /*
@@ -2433,10 +2553,10 @@ cleanup_transaction:
  * because btrfs_commit_super will poke cleaner thread and it will process it a
  * few seconds later.
  */
-int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
+int btrfs_clean_one_deleted_snapshot(struct btrfs_fs_info *fs_info)
 {
+	struct btrfs_root *root;
 	int ret;
-	struct btrfs_fs_info *fs_info = root->fs_info;
 
 	spin_lock(&fs_info->trans_lock);
 	if (list_empty(&fs_info->dead_roots)) {