James Bottomley wrote: > On Wed, 2008-03-05 at 01:42 +0900, Tejun Heo wrote: >> Tejun Heo wrote: >>> Tejun Heo wrote: >>>> FUJITA Tomonori wrote: >>>>>> Aiee... device going down after timing out on READ_DISC_INFO. That's >>>>>> gruesome. Can you please try the other patches? >>>>> Tejun, I thought that libata needs a fix for sum(sg) != rq->data_len. No? >>>> The extra_len you added to qc->nbytes should be it. The only other >>>> place to pay attention is the ATAPI transfer chunk size and your patch >>>> seems to get it right. >>>> >>>>> Now Jens' git tree should work with all the non libata stuff, ide, >>>>> firewire, bsg, etc. But I'm not sure about libata. >>>> With the second patch, all others should be fine no matter what. I'll >>>> go check libata part again. >>> I can reproduce the problem here and it's very weird. I'll report back >>> when I know more. >> Okay, I got it. Heh, it turns out SCSI and/or block layer is not >> ready for rq->data_len != sum(sg). When adjusted command completes, >> SCSI midlayer completes the command with rq->data_len for PC commands >> which eventually ends up in __end_that_request_first(). As there are >> extra sg area left after completing rq->data_len, blk layer says so to >> SCSI layer and SCSI layer retries the command only with the appended >> area. >> >> The following patch gets the writing going. I really think it's a >> serious mistake to break rq->data_len == sum(sg). If we break >> rq->data_len == requested size, the worst bugs are giving wrong size >> when issuing commands to application layer of devices which is >> relatively easy to spot and not all that command anyway. Breaking >> rq->data_len == sum(sg), bugs will be in internal mechanics, DMA >> engine programming and transport layer. Oh well... >> >> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c >> index fecba05..32439ac 100644 >> --- a/drivers/scsi/scsi.c >> +++ b/drivers/scsi/scsi.c >> @@ -757,7 +757,7 @@ void scsi_finish_command(struct scsi_cmnd *cmd) >> "Notifying upper driver of completion " >> "(result %x)\n", cmd->result)); >> >> - good_bytes = scsi_bufflen(cmd); >> + good_bytes = scsi_bufflen(cmd) + cmd->request->data_len; > > This doesn't look right. scsi_bufflen(cmd) is req->data_len for PC > commands ... did you mean to add extra_len here? Yeap, sorry about the confusion. Adding two times data_len accidentally worked tho. :-) -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
