On Tue, May 08 2007, James Bottomley wrote: > On Tue, 2007-05-08 at 18:40 +0200, Jens Axboe wrote: > > On Tue, May 08 2007, 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@xxxxxxxxxx> > > > > > > > > Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx> > > > > > > > > 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). > > > > Of course, bouncing should only be done in one layer (the block layer). > > > > > > 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 > > > > > > Can we just merge this instead? > > > > That's another issue. The problem here are requests (cgc's) initiated by > > the cdrom.c layer. Those _should_ get mapped to a request and put on the > > queue for the device, and thus get bounced by the block layer if > > appropriate. > > > > Mike's fix looks legit and should be merged as well, but it wont fix > > this issue. > > It won't? I thought the issue (from the fix) is that cgc->buffer is > outside of the device accessibility mask. The scsi_execute path > allocates a request and then calls blk_rq_map_kern on the buffer (in > this case cgc->buffer) ... the problem is that blk_rq_map_kern() doesn't > currently bounce the buffer, but if it did (which is the functionality > Mike's patch adds), surely the need to bounce it in the ioctl path would > go away? You are right, I missed that scsi_execute() actually builds a request in the proper manner. Mikes patch is in the for-2.6.22 block branch and I asked Linus to pull, so all should be well. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
