ext4: do not iput inode under running transaction in ext4_rename()

In ext4_rename(), when RENAME_WHITEOUT failed to add new entry into
directory, it ends up dropping new created whiteout inode under the
running transaction. After commit <9b88f9fb> ("ext4: Do not iput inode
under running transaction"), we follow the assumptions that evict() does
not get called from a transaction context but in ext4_rename() it breaks
this suggestion. Although it's not a real problem, better to obey it, so
this patch add inode to orphan list and stop transaction before final
iput().
Signed-off-by: Nzhangyi (F) <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/20210303131703.330415-2-yi.zhang@huawei.comSigned-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/namei.c

@@ -3799,14 +3799,14 @@ static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 	 */
 	retval = -ENOENT;
 	if (!old.bh || le32_to_cpu(old.de->inode) != old.inode->i_ino)
-		goto end_rename;
+		goto release_bh;
 
 	new.bh = ext4_find_entry(new.dir, &new.dentry->d_name,
 				 &new.de, &new.inlined);
 	if (IS_ERR(new.bh)) {
 		retval = PTR_ERR(new.bh);
 		new.bh = NULL;
-		goto end_rename;
+		goto release_bh;
 	}
 	if (new.bh) {
 		if (!new.inode) {
@@ -3823,15 +3823,13 @@ static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 		handle = ext4_journal_start(old.dir, EXT4_HT_DIR, credits);
 		if (IS_ERR(handle)) {
 			retval = PTR_ERR(handle);
-			handle = NULL;
-			goto end_rename;
+			goto release_bh;
 		}
 	} else {
 		whiteout = ext4_whiteout_for_rename(mnt_userns, &old, credits, &handle);
 		if (IS_ERR(whiteout)) {
 			retval = PTR_ERR(whiteout);
-			whiteout = NULL;
-			goto end_rename;
+			goto release_bh;
 		}
 	}
 
@@ -3965,16 +3963,18 @@ static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 			ext4_resetent(handle, &old,
 				      old.inode->i_ino, old_file_type);
 			drop_nlink(whiteout);
+			ext4_orphan_add(handle, whiteout);
 		}
 		unlock_new_inode(whiteout);
+		ext4_journal_stop(handle);
 		iput(whiteout);
-
+	} else {
+		ext4_journal_stop(handle);
 	}
+release_bh:
 	brelse(old.dir_bh);
 	brelse(old.bh);
 	brelse(new.bh);
-	if (handle)
-		ext4_journal_stop(handle);
 	return retval;
 }