linux-kernel - [PATCH] return ENOENT from ext3

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Message-ID: <45ABC572.2070206@redhat.com>
Date:	Mon, 15 Jan 2007 12:18:26 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	linux-kernel Mailing List <linux-kernel@...r.kernel.org>,
	ext4 development <linux-ext4@...r.kernel.org>
CC:	dmonakhov@...ru, alex@...sterfs.com,
	Al Viro <viro@....linux.org.uk>
Subject: [PATCH] return ENOENT from ext3_link when racing with unlink

An update from the earlier thread, 
[PATCH] [RFC] remove ext3 inode from orphan list when link and unlink race

I think this is better than the original idea of trying to handle the race;
I've seen that the orphan inode list can get corrupted, but there may well
be other implications of the race which haven't yet been exposed.  I think
it's safer to simply return -ENOENT in this race window, and avoid other
potential problems.  Anything wrong with this?

Thanks for the comments suggesting this approach in the prior thread.

Thanks,

-Eric

---

Return -ENOENT from ext[34]_link if we've raced with unlink and
i_nlink is 0.  Doing otherwise has the potential to corrupt the
orphan inode list, because we'd wind up with an inode with a
non-zero link count on the list, and it will never get properly
cleaned up & removed from the orphan list before it is freed.

Signed-off-by: Eric Sandeen <sandeen@...hat.com>

Index: linux-2.6.19/fs/ext3/namei.c
===================================================================
--- linux-2.6.19.orig/fs/ext3/namei.c
+++ linux-2.6.19/fs/ext3/namei.c
@@ -2191,6 +2191,8 @@ static int ext3_link (struct dentry * ol

 	if (inode->i_nlink >= EXT3_LINK_MAX)
 		return -EMLINK;
+	if (inode->i_nlink == 0)
+		return -ENOENT;

 retry:
 	handle = ext3_journal_start(dir, EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +
Index: linux-2.6.19/fs/ext4/namei.c
===================================================================
--- linux-2.6.19.orig/fs/ext4/namei.c
+++ linux-2.6.19/fs/ext4/namei.c
@@ -2189,6 +2189,8 @@ static int ext4_link (struct dentry * ol

 	if (inode->i_nlink >= EXT4_LINK_MAX)
 		return -EMLINK;
+	if (inode->i_nlink == 0)
+		return -ENOENT;

 retry:
 	handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +

-
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