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Date: Fri, 13 Jan 2006 13:21:36 +0300
From: Alexey Dobriyan <adobriyan@gmail.com>
To: Linus Torvalds <torvalds@osdl.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: Oops in ufs_fill_super at mount time
Message-ID: <20060113102136.GA7868@mipter.zuzino.mipt.ru>
References: <20060113005450.GA7971@mipter.zuzino.mipt.ru> <Pine.LNX.4.64.0601121700041.3535@g5.osdl.org>
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On Thu, Jan 12, 2006 at 05:14:25PM -0800, Linus Torvalds wrote:
> On Fri, 13 Jan 2006, Alexey Dobriyan wrote:
> >
> > Version 2.6.15-43ecb9a33ba8c93ebbda81d48ca05f0d1bbf9056
> >
> > Actually more or less latest -git is affected too, but
> > I'm sick of recompiling right now so please wait for bisecting results.
>
> Hmm.. I don't see any recent changes that could affect this. Not after
> 2.6.15, but in fact not even after 2.6.14.
>
> Your oops is also interesting in another way...
>
> > Unable to handle kernel paging request at virtual address d734c158
> >  printing eip:
> > c019f138
> > *pde = 0005c067
> > *pte = 1734c000
> > Oops: 0000 [#1]
> > PREEMPT DEBUG_PAGEALLOC
>
> This is a free'd page fault, so it's due to DEBUG_PAGEALLOC rather than a
> wild pointer.

That's true. Turning it off makes mounting reliable again.

> Is that something new for you? Maybe the bug is older, but you've enabled
> PAGEALLOC only recently?

Yup. In response to hangs re disk activity.

> Also, out of interest, have you enabled slab
> debugging?

Yup.

> That said, the whole ubh_get_usb_second() and ubh_get_usb_third() thing is
> pretty damn scary. There's no testing of the values passed in at all and
> comparing them to the allocated buffer heads. But from what I can tell,
> ubh_bread_uspi() will zero out any unallocated bh's, and it certainly
> _looks_ like the calculations to calculate "usb2" should fit within the
> sectors that were read..
>
> Very strange.