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Re: reproducible xfs/vmap oops

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: reproducible xfs/vmap oops
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 4 Feb 2009 08:42:45 +1100
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20090203210423.GA26628@xxxxxxxxxxxxx>
Mail-followup-to: Christoph Hellwig <hch@xxxxxxxxxxxxx>, Nick Piggin <nickpiggin@xxxxxxxxxxxx>, xfs@xxxxxxxxxxx
References: <20090201081224.GA22398@xxxxxxxxxxxxx> <20090201161458.GA5930@xxxxxxxxxxxxx> <20090203155147.GB21278@xxxxxxxxxxxxx> <200902040303.13933.nickpiggin@xxxxxxxxxxxx> <20090203160515.GA30986@xxxxxxxxxxxxx> <20090203184409.GA22204@xxxxxxxxxxxxx> <20090203210423.GA26628@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Feb 03, 2009 at 04:04:23PM -0500, Christoph Hellwig wrote:
> [ 3138.799436] XFS mounting filesystem vde
> [ 3138.813184] va->va_start = 4290777088, va->va_end = 4096
> [ 3138.834754] tmp->va_start = 4195352576, tmp->va_end = 4196401152
> [ 3138.846352] ------------[ cut here ]------------
> [ 3138.850332] kernel BUG at mm/vmalloc.c:298!
> [ 3138.850332] invalid opcode: 0000 [#1] SMP 
> 
> The first va_end looks suspicious to me..

That is on i386, Christoph? If so, I'd suspect a 32 bit overflow
as 4290777088 = 0xFFC01000 and va_start/va_end are unsigned longs.
If we tried to map exactly 4MB the with va_start at 0xFFC01000 we'd
end up with va_end at 0x100001000 which would wrap to 0x1000 = 4096.

Nick - this one is probably yours ;)

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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