1 files changed, 44 insertions, 0 deletions
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index a2bae5c230e1..7dd7552f53a4 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -4823,6 +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