ext3: Replace lock/unlock_super() with an explicit lock for the orphan list

Use a separate lock to protect the orphan list, so we can stop
overloading the use of lock_super().

Port of ext4 commit 3b9d4ed26680771295d904a6b83e88e620780893
by Theodore Ts'o <[e-mail]>.

CC: Theodore Ts'o <[e-mail]>
Signed-off-by: Eric Sandeen <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/ext3/namei.c

···
 	struct ext3_iloc iloc;
 	int err = 0, rc;
 
-	lock_super(sb);
+	mutex_lock(&EXT3_SB(sb)->s_orphan_lock);
 	if (!list_empty(&EXT3_I(inode)->i_orphan))
 		goto out_unlock;
 
···
 
 	/* @@@ FIXME: Observation from aviro:
 	 * I think I can trigger J_ASSERT in ext3_orphan_add().  We block
-	 * here (on lock_super()), so race with ext3_link() which might bump
+	 * here (on s_orphan_lock), so race with ext3_link() which might bump
 	 * ->i_nlink. For, say it, character device. Not a regular file,
 	 * not a directory, not a symlink and ->i_nlink > 0.
+	 *
+	 * tytso, 4/25/2009: I'm not sure how that could happen;
+	 * shouldn't the fs core protect us from these sort of
+	 * unlink()/link() races?
 	 */
 	J_ASSERT ((S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
 		S_ISLNK(inode->i_mode)) || inode->i_nlink == 0);
···
 	jbd_debug(4, "orphan inode %lu will point to %d\n",
 			inode->i_ino, NEXT_ORPHAN(inode));
 out_unlock:
-	unlock_super(sb);
+	mutex_unlock(&EXT3_SB(sb)->s_orphan_lock);
 	ext3_std_error(inode->i_sb, err);
 	return err;
 }
···
 	struct ext3_iloc iloc;
 	int err = 0;
 
-	lock_super(inode->i_sb);
-	if (list_empty(&ei->i_orphan)) {
-		unlock_super(inode->i_sb);
-		return 0;
-	}
+	mutex_lock(&EXT3_SB(inode->i_sb)->s_orphan_lock);
+	if (list_empty(&ei->i_orphan))
+		goto out;
 
 	ino_next = NEXT_ORPHAN(inode);
 	prev = ei->i_orphan.prev;
···
 out_err:
 	ext3_std_error(inode->i_sb, err);
 out:
-	unlock_super(inode->i_sb);
+	mutex_unlock(&EXT3_SB(inode->i_sb)->s_orphan_lock);
 	return err;
 
 out_brelse:

fs/ext3/super.c

···
 	sb->dq_op = &ext3_quota_operations;
 #endif
 	INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
+	mutex_init(&sbi->s_orphan_lock);
 
 	sb->s_root = NULL;
 

include/linux/ext3_fs_sb.h

···
 	struct inode * s_journal_inode;
 	struct journal_s * s_journal;
 	struct list_head s_orphan;
+	struct mutex s_orphan_lock;
 	unsigned long s_commit_interval;
 	struct block_device *journal_bdev;
 #ifdef CONFIG_JBD_DEBUG