linux-kernel - Re: xfslogd-spinlock bug?

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Date:	Tue, 19 Dec 2006 00:39:46 +0100
From:	Haar János <djani22@...center.hu>
To:	"David Chinner" <dgc@....com>
Cc:	<dgc@....com>, <linux-xfs@....sgi.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: xfslogd-spinlock bug?


----- Original Message ----- 
From: "David Chinner" <dgc@....com>
To: "Haar János" <djani22@...center.hu>
Cc: "David Chinner" <dgc@....com>; <linux-xfs@....sgi.com>;
<linux-kernel@...r.kernel.org>
Sent: Monday, December 18, 2006 11:36 PM
Subject: Re: xfslogd-spinlock bug?


> On Mon, Dec 18, 2006 at 09:17:50AM +0100, Haar János wrote:
> > From: "David Chinner" <dgc@....com>
> > > > The NBD serves through eth1, and it is on the CPU3, but the ide0 is
on
> > the
> > > > CPU0.
> > >
> > > I'd say your NBD based XFS filesystem is having trouble.
> > >
> > > > > Are you using XFS on a NBD?
> > > >
> > > > Yes, on the 3. source.
> > >
> > > Ok, I've never heard of a problem like this before and you are doing
> > > something that very few ppl are doing (i.e. XFS on NBD). I'd start
> > > Hence  I'd start by suspecting a bug in the NBD driver.
> >
> > Ok, if you have right, this also can be in context with the following
issue:
> >
> > http://download.netcenter.hu/bughunt/20061217/messages.txt   (10KB)
>
> Which appears to be a crash in wake_up_process() when doing memory
> reclaim (waking the xfsbufd).

Sorry, can you translate it to "poor mans language"? :-)
This is a different bug?


>
> > > > > > Dec 16 12:08:36 dy-base RSP: 0018:ffff81011fdedbc0  EFLAGS:
00010002
> > > > > > Dec 16 12:08:36 dy-base RAX: 0000000000000033 RBX:
6b6b6b6b6b6b6b6b
> > RCX:
> > > > >
^^^^^^^^^^^^^^^^
> > > > > Anyone recognise that pattern?
>
> Ok, I've found this pattern:
>
> #define POISON_FREE 0x6b
>
> Can you confirm that you are running with CONFIG_DEBUG_SLAB=y?

Yes, i build with this option enabled.
Is this wrong?

>
> If so, we have a use after free occurring here and it would also
> explain why no-one has reported it before.
>
> FWIW, can you turn on CONFIG_XFS_DEBUG=y and see if that triggers
> a different bug check prior to the above dump?

[root@X64 linux-2.6.19]# make bzImage
scripts/kconfig/conf -s arch/x86_64/Kconfig
.config:7:warning: trying to assign nonexistent symbol XFS_DEBUG

I have missed something?


Thanks,

Janos

>
> Cheers,
>
> Dave.
> -- 
> Dave Chinner
> Principal Engineer
> SGI Australian Software Group

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