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Re: Direct I/O bug in kernel

To: Hillf Danton <dhillf@gmail.com>
Subject: Re: Direct I/O bug in kernel
From: Victor Meyerson <calculuspenguin@yahoo.com>
Date: Thu, 9 Aug 2012 13:53:14 -0700 (PDT)
Cc: "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>, Ralf Baechle <ralf@linux-mips.org>, LKML <linux-kernel@vger.kernel.org>
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Reply-to: Victor Meyerson <calculuspenguin@yahoo.com>
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----- Original Message -----

> From: Hillf Danton <dhillf@gmail.com>
> To: Victor Meyerson <calculuspenguin@yahoo.com>
> Cc: "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>; Ralf Baechle 
> <ralf@linux-mips.org>; LKML <linux-kernel@vger.kernel.org>
> Sent: Friday, July 27, 2012 7:47 AM
> Subject: Re: Direct I/O bug in kernel
> 
> On Wed, Jul 25, 2012 at 1:28 AM, Victor Meyerson
> <calculuspenguin@yahoo.com> wrote:
>> 
>>  Still different checksums and I used the same random-file from my first 
> test.
>> 
> Then try the fix at
>             https://lkml.org/lkml/2012/7/27/54
> 

I tried that patch, although I had to edit a slightly different line as 
dio_bio_alloc was near line 392 instead of 349 in the version of fs/direct-io.c 
in my tree.  I still got different checksums between the two files and even 
different checksums from my earlier attempts.

I am not sure if this helps, but Ralf asked if I can try a different page size 
to see if this problem occurs.  I originally had CONFIG_PAGE_SIZE_4KB=y and 
changed it to CONFIG_PAGE_SIZE_16KB=y (via menuconfig).  Having a page size of 
16KB (and the above patch not applied) made the checksum on the files match 
each other and match the file made from the working kernel.

Victor


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