linux-kernel - Re: 2.6.21 reiserfs -- cicular locking?

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Message-ID: <463222F5.7080209@suse.de>
Date:	Fri, 27 Apr 2007 12:21:09 -0400
From:	Jeff Mahoney <jeffm@...e.de>
To:	Jeff Mahoney <jeffm@...e.com>
Cc:	Takashi Iwai <tiwai@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Brownell <david-b@...bell.net>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	reiserfs-dev@...esys.com
Subject: Re: 2.6.21 reiserfs -- cicular locking?

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Jeff Mahoney wrote:
> Takashi Iwai wrote:
>>> At Fri, 27 Apr 2007 07:09:01 -0400,
>>> Jeff Mahoney wrote:
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>>>>
>>>> Takashi Iwai wrote:
>>>>> At Fri, 27 Apr 2007 12:09:03 +0200,
>>>>> I wrote:
>>>>>> I got a similar bug right now at the fresh boot of 2.6.21.
>>>>>>
>>>>>>
>>>>>> ReiserFS: sda2: found reiserfs format "3.6" with standard journal
>>>>>> ReiserFS: sda2: using ordered data mode
>>>>>> ReiserFS: sda2: journal params: device sda2, size 8192, journal first block 18, max trans len 1024, max batch 900, max commit age 30, max trans age 30
>>>>>> ReiserFS: sda2: checking transaction log (sda2)
>>>>>> ReiserFS: sda2: Using r5 hash to sort names
>>>>>> ReiserFS: sda2: Removing [3613 1354701 0x0 SD]..done
>>>>>> ReiserFS: sda2: There were 1 uncompleted unlinks/truncates. Completed
>>>>>>
>>>>>> =======================================================
>>>>>> [ INFO: possible circular locking dependency detected ]
>>>>>> 2.6.21-work #1
>>>>>> -------------------------------------------------------
>>>>>> mktemp/1459 is trying to acquire lock:
>>>>>>  (&REISERFS_I(inode)->xattr_sem){..--}, at: [<e08a5236>] reiserfs_cache_default_acl+0x2a/0x9c [reiserfs]
>>>>>>
>>>>>> but task is already holding lock:
>>>>>>  (&inode->i_mutex){--..}, at: [<c016d7dc>] open_namei+0xe2/0x5a2
>>>>>>
>>>>>> which lock already depends on the new lock.
>>>>> The message disappears when I revert the patch:
>>>>>
>>>>> commit 9b7f375505f5611efb562065b57814b28a81abc3
>>>>> Author: Jeff Mahoney <jeffm@...e.com>
>>>>> Date:   Mon Apr 23 14:41:17 2007 -0700
>>>>>
>>>>>     reiserfs: fix xattr root locking/refcount bug
>>>>>     
>>>>>
>>>>> So, likely a newly introduced bug after rc7...
>>>> I got a message with a trace similar to this from Vladimir before I
>>>> submitted that patch. I'm not sure how to annotate this, since the
>>>> xattr_sem can never be taken in the manner described. Internal inodes
>>>> are protected by I_PRIVATE.
>>> Hm, then maybe my case was just a coincidence.
>>>
>>> FWIW, I can reproduce the deadlock warning at each time I boot
>>> non-patched 2.6.21, and after reverting the patch, it disappeared.
> 
> Ok, so I took another look at the report Vladimir sent me. The trace he
> ran into was in the delete inode path, but was still a race between the
> xattr_sem and the inode sem. Since we're locking the xattr root on the
> xattr read path now, this condition arises more freqently, but it's
> really the same one he reported.
> 
> I'm using the default openSUSE config, which doesn't enable mutex
> debugging. I'll rebuild with it, and hopefully come up with a way to
> kill the warning.

I still didn't get the warning, but can you try this and let me know
if it fixes it?

- -Jeff

- --- a/fs/reiserfs/xattr.c	2007-04-22 10:53:10.000000000 -0400
+++ b/fs/reiserfs/xattr.c	2007-04-27 12:09:02.000000000 -0400
@@ -68,7 +68,7 @@
 	if (!privroot)
 		return ERR_PTR(-ENODATA);
 
- -	mutex_lock(&privroot->d_inode->i_mutex);
+	mutex_lock_nested(&privroot->d_inode->i_mutex, I_MUTEX_XATTR);
 	if (REISERFS_SB(sb)->xattr_root) {
 		xaroot = dget(REISERFS_SB(sb)->xattr_root);
 		goto out;

- -- 
Jeff Mahoney
SUSE Labs
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