linux-ext4 - Re: [PATCH 5/5 v6] ext4: fix partial page writes

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Date:	Fri, 26 Aug 2011 15:46:44 -0700
From:	Allison Henderson <achender@...ux.vnet.ibm.com>
To:	"Ted Ts'o" <tytso@....edu>
CC:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 5/5 v6] ext4: fix partial page writes

On 08/26/2011 08:47 AM, Ted Ts'o wrote:
> On Wed, Aug 24, 2011 at 12:07:22PM -0700, Allison Henderson wrote:
>> While running extended fsx tests to verify the preceeding patches,
>> a similar bug was also found in the write operation
>>
>> When ever a write operation begins or ends in a hole,
>> or extends EOF, the partial page contained in the hole
>> or beyond EOF needs to be zeroed out.
>>
>> To correct this the new ext4_discard_partial_page_buffers_no_lock
>> routine is used to zero out the partial page, but only for buffer
>> heads that are already unmapped.
>>
>> Signed-off-by: Allison Henderson<achender@...ux.vnet.ibm.com>
>
> I haven't had a chance to debug this yet, but FYI, with this patch
> applied, xfstests #224 causes OOM's to result when running under KVM
> with 1024megs.  I tried doubling the memory to 2048 megs, and it
> passed in 4k standard ext4 mode, but then got hit with the OOM killer
> on test #224 in ext3 emulation mode (nodealloc, and with extents not
> enabled in the file system).  Without this patch, and the first four
> patches in the v6 patch series applied, xfstests #224 passes in all of
> the standard configurations (4k, ext3, 1k, data=journal, etc.)
>
> I don't know why this is happening, but I'll try to dig into it in the
> next day or two.  Any thoughts or fixes you might suggest would be
> much appreciated.
>
> 						- Ted

Alrighty then, I will look into this one and see if I can figure out 
whats going on.  Thx again!

Allison Henderson

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