linux-ext4 - Re: [PATCH] [RFC] remove ext3 inode from orphan list when link and unlink race

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Date:	Fri, 12 Jan 2007 16:35:08 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Eric Sandeen <sandeen@...hat.com>
CC:	Alex Tomas <alex@...sterfs.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ext4 development <linux-ext4@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] [RFC] remove ext3 inode from orphan list when link and
 unlink race

Eric Sandeen wrote:

> Alex Tomas wrote:
>   
>> yes, but it shouldn't allow to re-link such inode back, IMHO.
>> a filesystem may start some non-revertable activity in its
>> unlink method.
>>
>> thanks, Alex
>>     
>
> I tend to agree, chatting w/ Al I think he does too.  :)  I'll test
> a patch that kicks out ext3_link() with -ENOENT at the top, and resubmit
> that if things go well.
>   
Well this seems to fix things up for ext3 (and ext4 by extension):

---

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.

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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