reiserfs: add missing unlock to an error path in reiserfs_quota_write()

When write in reiserfs_quota_write() fails, we have to properly release
i_mutex. One error path has been missing the unlock...
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/reiserfs/super.c

@@ -2165,8 +2165,10 @@ static ssize_t reiserfs_quota_write(struct super_block *sb, int type,
 		blk++;
 	}
 out:
-	if (len == towrite)
+	if (len == towrite) {
+		mutex_unlock(&inode->i_mutex);
 		return err;
+	}
 	if (inode->i_size < off + len - towrite)
 		i_size_write(inode, off + len - towrite);
 	inode->i_version++;