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: <x49lj8kc0xf.fsf@segfault.boston.devel.redhat.com>
Date:	Thu, 05 Aug 2010 15:30:20 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Vladislav Bolkhovitin <vst@...b.net>
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

Vladislav Bolkhovitin <vst@...b.net> writes:

> 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.

Thanks a ton!

-Jeff
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