Merge branch 'sched/urgent' into sched/core, to pick up fixes and refresh the branch

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 0cb1dee965a0..b2e5107b7cec 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -3028,8 +3028,16 @@ static int update_block_group_item(struct btrfs_trans_handle *trans,
 	btrfs_mark_buffer_dirty(leaf);
 fail:
 	btrfs_release_path(path);
-	/* We didn't update the block group item, need to revert @commit_used. */
-	if (ret < 0) {
+	/*
+	 * We didn't update the block group item, need to revert commit_used
+	 * unless the block group item didn't exist yet - this is to prevent a
+	 * race with a concurrent insertion of the block group item, with
+	 * insert_block_group_item(), that happened just after we attempted to
+	 * update. In that case we would reset commit_used to 0 just after the
+	 * insertion set it to a value greater than 0 - if the block group later
+	 * becomes with 0 used bytes, we would incorrectly skip its update.
+	 */
+	if (ret < 0 && ret != -ENOENT) {
 		spin_lock(&cache->lock);
 		cache->commit_used = old_commit_used;
 		spin_unlock(&cache->lock);