linux-kernel - Re: [BUG] 2.6.29-rc6-2450cf in scsi_lib.c (was: Large amount of scsi-sgpool)objects

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Date:	Thu, 5 Mar 2009 12:10:40 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	tglx@...utronix.de, James.Bottomley@...senPartnership.com,
	jengelh@...ozas.de, bharrosh@...asas.com,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-ide@...r.kernel.org
Subject: Re: [BUG] 2.6.29-rc6-2450cf in scsi_lib.c (was: Large amount of
	scsi-sgpool)objects

On Thu, Mar 05 2009, FUJITA Tomonori wrote:
> On Thu, 5 Mar 2009 11:30:24 +0100
> Jens Axboe <jens.axboe@...cle.com> wrote:
> 
> > > > While merging that, I think we can do better than this. Essentially we
> > > > just need to have __blk_recalc_rq_segments() track the back bio as well,
> > > > then we don't have to pass in a pointer for segment sizes.
> > > > 
> > > > Totally untested, comments welcome...
> > > 
> > > Yeah, I think that updating bi_seg_front_size and bi_seg_back_size at
> > > one place, __blk_recalc_rq_segments, is better. I thought about the
> > > same way. But we are already in -rc7 and this must go into mainline
> > > now. So I chose a less-intrusive way (similar to what we have done in
> > > the past).
> > > 
> > > As you know, the merging code is really complicated and we could
> > > overlook stuff easily. ;) It might be better to simplify the merging
> > > code a bit.
> > 
> > If someone (Ingo?) is willing to test the last variant, I'd much rather
> > add that. It does simplify it (imho), and it kills 23 lines while only
> > adding 9. But a quick response would be nice, then I can ask Linus to
> > pull it later today.
> 
> I prefer to keep your change for 2.6.30 but if you want to push it
> now, it's fine by me.

I honestly can't see much of a difference in change complexity, so I
don't see much point in putting one fix in 2.6.29 and then doing another
for 2.6.30...

> Ingo, you can quickly hit this bug without the patch?
> 
> I've not hit this bug while I've been performing intensive I/Os for
> the last three hours. And I thought that Thomas took two hours to hit
> this. So maybe it's too early to give 'Tested-by'. With 
> max_segment_size decreased, we might hit this easier.

Yep, that may help. I haven't seen this thread until I was cc'ed on it,
so I haven't even read up on the generic problem yet...

-- 
Jens Axboe

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