linux-kernel - Re: [PATCH 14/17] scsi: replace custom rq mapping with blk_rq_map_kern

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Date:	Thu, 16 Apr 2009 15:30:29 +0900
From:	Tejun Heo <tj@...nel.org>
To:	petkovbb@...il.com, Tejun Heo <tj@...nel.org>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	bharrosh@...asas.com, James.Bottomley@...senpartnership.com,
	linux-scsi@...r.kernel.org, axboe@...nel.dk, bzolnier@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/17] scsi: replace custom rq mapping with	blk_rq_map_kern_sgl()

Borislav Petkov wrote:
> Hi Tejun,
> 
> On Thu, Apr 16, 2009 at 03:07:09PM +0900, Tejun Heo wrote:
> 
> [..]
> 
>> There was another problem.  If we use blk_rq_map_kern() the failed rq
>> must be finished after the sense rq is finished because that's when
>> the bio is copied back if it was copied.  Before sense_rq completion,
>> the sense buffer doesn't contain any valid data.
> 
> Well, as an idea, we could just postpone the completion of the failed rq
> in:
> 
> if (sense && uptodate)
>         ide_cd_complete_failed_rq(drive, rq);
> 
> and put that just after
> 
> ide_complete_rq(drive, uptodate ? 0 : -EIO, nsectors << 9);
> 
> line in cdrom_newpc_intr(). This way, we can copy back the sense data
> safely and then kill the rq.

Yeah, already have that in my patch.

> The only problem I fear with changes like that is that later some subtle
> interactions come about with some device which shouldn't normally
> happen. This is old code, you know, which still needs lots of scrubbing.
> It's like walking on a minefield :).

:-)

-- 
tejun
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