1 files changed, 27 insertions, 3 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index a5e08a73653e..0dba09334a16 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -5580,9 +5580,33 @@ static int btrfs_log_all_parents(struct btrfs_trans_handle *trans,
 
                         dir_inode = btrfs_iget(fs_info->sb, &inode_key,
                                                root, NULL);
-                        /* If parent inode was deleted, skip it. */
-                        if (IS_ERR(dir_inode))
-                                continue;
+                        /*
+                         * If the parent inode was deleted, return an error to
+                         * fallback to a transaction commit. This is to prevent
+                         * getting an inode that was moved from one parent A to
+                         * a parent B, got its former parent A deleted and then
+                         * it got fsync'ed, from existing at both parents after
+                         * a log replay (and the old parent still existing).
+                         * Example:
+                         *
+                         * mkdir /mnt/A
+                         * mkdir /mnt/B
+                         * touch /mnt/B/bar
+                         * sync
+                         * mv /mnt/B/bar /mnt/A/bar
+                         * mv -T /mnt/A /mnt/B
+                         * fsync /mnt/B/bar
+                         * <power fail>
+                         *
+                         * If we ignore the old parent B which got deleted,
+                         * after a log replay we would have file bar linked
+                         * at both parents and the old parent B would still
+                         * exist.
+                         */
+                        if (IS_ERR(dir_inode)) {
+                                ret = PTR_ERR(dir_inode);
+                                goto out;
+                        }
 
                         if (ctx)
                                 ctx->log_new_dentries = false;