linux-kernel - Re: [PATCH RESEND 1/2 block#for-linus] bio, fs: update READA and SWRITE to match the corresponding BIO_RW

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Message-ID: <4C5B0994.1070203@vlnb.net>
Date:	Thu, 05 Aug 2010 22:57:24 +0400
From:	Vladislav Bolkhovitin <vst@...b.net>
To:	Jeff Moyer <jmoyer@...hat.com>
CC:	Tejun Heo <tj@...nel.org>, Jens Axboe <jens.axboe@...nel.dk>,
	stable@...nel.org, Bryan Mesich <bryan.mesich@...u.edu>,
	scst-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-raid@...r.kernel.org, dm-devel@...hat.com,
	Neil Brown <neilb@...e.de>
Subject: Re: [PATCH RESEND 1/2 block#for-linus] bio, fs: update READA and
 SWRITE to match the corresponding BIO_RW_* bits


Jeff Moyer, on 08/05/2010 10:45 PM wrote:
> Tejun Heo<tj@...nel.org>  writes:
>
>> Commit a82afdf (block: use the same failfast bits for bio and request)
>> moved BIO_RW_* bits around such that they match up with REQ_* bits.
>> Unfortunately, fs.h hard coded READ, WRITE, READA and SWRITE as 0, 1,
>> 2 and 3, and expected them to match with BIO_RW_* bits.  READ/WRITE
>> didn't change but BIO_RW_AHEAD was moved to bit 4 instead of bit 1,
>> breaking READA and SWRITE.
>>
>> This patch updates READA and SWRITE such that they match the BIO_RW_*
>> bits again.  A follow up patch will update the definitions to directly
>> use BIO_RW_* bits so that this kind of breakage won't happen again.
>>
>> Stable: The offending commit a82afdf was released with v2.6.32, so
>> this patch should be applied to all kernels since then but it must
>> _NOT_ be applied to kernels earlier than that.
>
> Would someone be so kind as to remind me how this problem manifests
> itself?  I know I read this recently, but my memory and googling skills
> are both failing me.  :(

See http://lkml.org/lkml/2010/7/28/315 and link inside.

Vlad
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