linux-kernel - Re: [PATCH]: Fix old SCSI adapter crashes with CD-ROM (take 2)

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Message-ID: <4640A972.3010108@cs.wisc.edu>
Date:	Tue, 08 May 2007 11:46:42 -0500
From:	Mike Christie <michaelc@...wisc.edu>
To:	James Bottomley <James.Bottomley@...elEye.com>
CC:	Jens Axboe <jens.axboe@...cle.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-scsi@...r.kernel.org, akpm@...l.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH]: Fix old SCSI adapter crashes with CD-ROM (take 2)

James Bottomley wrote:
> On Tue, 2007-05-08 at 18:14 +0200, Jens Axboe wrote:
>> On Tue, May 08 2007, Alan Cox wrote:
>>> The CD-ROM layer doesn't bounce requests for old ISA controllers (and
>>> nor should it). However they get injected into the SCSI layer via
>>> sr_ioctl which also doesn't bounce them and SCSI then passes the buffer
>>> along to a device with unchecked_isa_dma set which either panics or
>>> truncates the buffer to 24bits.
>>>
>>> According to Jens the right long term fix is for the CD layer to route
>>> the requests differently but in the mean time this has been tested by a
>>> victim and verified to sort the problem out. For the other 99.9% of users
>>> it's a no-op and doesn't bounce data.
>>>
>>> Signed-off-by: Alan Cox <alan@...hat.com>
>> Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
>>
>> Christoph passed me his patch to get rid of ->generic_packet() in the
>> cdrom layer, so the work is almost complete. This patch is fine as a
>> work-around until that gets merged, though.
> 
> Actually, I think the new scsi request infrastructure should be doing
> the bouncing (rather than have it done in each problem path we
> discover).
> 
> Mike Christie tells me we're missing bouncing by accident in the
> scsi_execute path (but not the scsi_execute_async path).  He says this
> is the fix he proposed:
> 
> http://marc.info/?l=linux-scsi&m=115981479822790&w=2
> 

Hey Jens and James, one thing I forgot to mention is that I could not
remember if I needed an extra bio_get in there. I thought I did not
because the caller is not touching the bio after the bio_endio calls
like is done with the blk/bio_map_user path. But I did that patch so
long ago I do not remember now.
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