linux-kernel - Re: IDE crash...

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Date:	Wed, 24 Oct 2007 08:49:00 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	John Stoffel <john@...ffel.org>
Cc:	David Miller <davem@...emloft.net>, fujita.tomonori@....ntt.co.jp,
	linux-kernel@...r.kernel.org
Subject: Re: IDE crash...

On Tue, Oct 23 2007, John Stoffel wrote:
> >>>>> "Jens" == Jens Axboe <jens.axboe@...cle.com> writes:
> 
> Jens> On Tue, Oct 23 2007, David Miller wrote:
> >> From: Jens Axboe <jens.axboe@...cle.com>
> >> Date: Tue, 23 Oct 2007 09:23:59 +0200
> >> 
> >> > On Tue, Oct 23 2007, David Miller wrote:
> >> > > From: Jens Axboe <jens.axboe@...cle.com>
> >> > > Date: Tue, 23 Oct 2007 09:09:33 +0200
> >> > > 
> >> > > > Eh this wont work, it's the wrong entry... Here's a temporary
> >> > > > work-around.
> >> > > > 
> >> > > > diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c
> >> > > > index c89f0d3..108202b 100644
> >> > > > --- a/drivers/ide/ide-io.c
> >> > > > +++ b/drivers/ide/ide-io.c
> >> > > > @@ -822,6 +822,7 @@ void ide_map_sg(ide_drive_t *drive, struct request *rq)
> >> > > >  		return;
> >> > > >  
> >> > > >  	if (rq->cmd_type != REQ_TYPE_ATA_TASKFILE) {
> >> > > > +		sg_init_table(hwif->sg_table, hwif->sg_max_nents);
> >> > > >  		hwif->sg_nents = blk_rq_map_sg(drive->queue, rq, sg);
> >> > > >  	} else {
> >> > > >  		sg_init_one(sg, rq->buffer, rq->nr_sectors * SECTOR_SIZE);
> >> > > 
> >> > > That's the exact patch I'm about to boot test :-)
> >> > 
> >> > That should work - once you verify that, would you mind testing this one
> >> > as well? Thanks!
> >> 
> >> This one works here too, thanks.
> 
> Jens> Great, thanks for testing that as well. Thinking a bit more
> Jens> about it, I think the forced clear should stay in
> Jens> blk_rq_map_sg() since we don't want to advertise it to
> Jens> drivers. So I'll just open-code it in there.
> 
> Should there be more bounds checking here, so that if you try to do a
> _force() you at least check to make sure that there's something beyond
> there and useable on the list?  
> 
> We're saving the time from not reallocating from scratch, but let's
> make it robust by doing at least some more checks here.

We have to rely on the caller passing in an sgtable that is big enough
to map the request, we have always made that assumption. Anything else
would be a bug, of course. Now, catching that bug would indeed be nice.
Any suggestions?

-- 
Jens Axboe

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