On Tue, May 08 2007, Mike Christie wrote:
> 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 <[email protected]>
> >> Signed-off-by: Jens Axboe <[email protected]>
> >>
> >> 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.
If you don't touch it after bio_endio(), then you don't need to hold an
extra reference to it. I'll add your patch.
--
Jens Axboe
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