linux-kernel - Re: [PATCH block#for-2.6.31 2/3] block: set rq->resid_len to blk_rq

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Date:	Sat, 16 May 2009 22:52:24 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Borislav Petkov <petkovbb@...il.com>, Tejun Heo <htejun@...il.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Boaz Harrosh <bharrosh@...asas.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	IDE/ATA development list <linux-ide@...r.kernel.org>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Borislav Petkov <petkovbb@...glemail.com>,
	Pete Zaitcev <zaitcev@...hat.com>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	Eric Moore <Eric.Moore@....com>,
	"Darrick J. Wong" <djwong@...ibm.com>
Subject: Re: [PATCH block#for-2.6.31 2/3] block: set rq->resid_len to	blk_rq_bytes()
 on issue

Hello, Borislav.

Borislav Petkov wrote:
> On Sat, May 16, 2009 at 12:18:42AM +0900, Tejun Heo wrote:
>> In commit c3a4d78c580de4edc9ef0f7c59812fb02ceb037f, while introducing
>> rq->resid_len, the default value of residue count was changed from
>> full count to zero.  The conversion was done under the assumption that
>> when a request fails residue count wasn't defined.  However, Boaz and
>> James pointed out that this wasn't true and the residue count should
>> be preserved for failed requests too.
>>
>> This patchset restores the original behavior by setting rq->resid_len
>> to blk_rq_bytes(rq) on issue and restoring explicit clearing in
>> affected drivers.  While at it, take advantage of the fact that
>> rq->resid_len is set to full count where applicable.
>>
>> * ide-cd: rq->resid_len cleared on pc success
>>
>> * mptsas: req->resid_len cleared on success
>>
>> * sas_expander: rsp/req->resid_len cleared on success
>>
>> * mpt2sas_transport: req->resid_len cleared on success
>>
>> * ide-cd, ide-tape, mptsas, sas_host_smp, mpt2sas_transport, ub: take
>>   advantage of initial full count to simplify code
> 
> ACK the ide-{cd,tape} bits.
> 
> Acked-by: Borislav Petkov <petkovbb@...il.com>
> 
> I've converted the ide-atapi part to rq->resid_len and from what I see,

Sorry it changed underneath your changes.

> the changes are compatible with the latest semantics of rq->resid_len
> but it won't hurt if you could take a look too :) :
>
> http://git.kernel.org/?p=linux/kernel/git/bp/bp.git;a=commit;h=077e6dba20e74a455a0452379d2a965c7e1b01ad

Yeap, I'll take a look.

> On a side note, ide_pc_intr() does some transfer padding but that
> doesn't affect rq->resid_len returning the remaining bytecount back up
> to block layer.

Hmmm... telling the issuer the actual number of transferred bytes sans
padding is the correct behavior, I think.

Thanks.

-- 
tejun
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