* Using scsi_cmd->request->nr_hw_segments within a LLDD...
@ 2004-09-21 21:55 Andrew Vasquez
2004-09-22 6:57 ` Jens Axboe
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Vasquez @ 2004-09-21 21:55 UTC (permalink / raw)
To: SCSI Mailing List
All,
Back in March the qla2xxx driver began to use the value in
cmd->request->nr_hw_segments as a guestimate during the calucation of
the number of driver-request-queue entries that would be needed to
fullfill a given command-request. Here's an URL to thread which
prompted the change:
http://marc.theaimsgroup.com/?l=linux-scsi&m=107940832718154&w=2
Recently we've had a number of problem reports which appear to
indicate that the value specified within the variable is
un-initialized and/or set to some bogus value.
Here's the relevant code the driver uses in qla2x00_start_scsi():
/* Calculate the number of request entries needed. */
req_cnt = (ha->calc_request_entries)(cmd->request->nr_hw_segments);
if (ha->req_q_cnt < (req_cnt + 2)) {
cnt = RD_REG_WORD_RELAXED(ISP_REQ_Q_OUT(ha, reg));
if (ha->req_ring_index < cnt)
ha->req_q_cnt = cnt - ha->req_ring_index;
else
ha->req_q_cnt = ha->request_q_length -
(ha->req_ring_index - cnt);
}
if (ha->req_q_cnt < (req_cnt + 2))
goto queuing_error;
The 'req_cnt' derived value in several instances is greater than 4000.
So, can an LLDD depend on the value being set to a proper value
during all I/O submission paths -- BIO as well as IOCTL?
If not, then what should a device driver writer use as an alternative?
Regards,
Andrew Vasquez
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: Using scsi_cmd->request->nr_hw_segments within a LLDD...
2004-09-21 21:55 Using scsi_cmd->request->nr_hw_segments within a LLDD Andrew Vasquez
@ 2004-09-22 6:57 ` Jens Axboe
2004-09-22 15:01 ` Patrick Mansfield
0 siblings, 1 reply; 4+ messages in thread
From: Jens Axboe @ 2004-09-22 6:57 UTC (permalink / raw)
To: Andrew Vasquez; +Cc: SCSI Mailing List
On Tue, Sep 21 2004, Andrew Vasquez wrote:
>
> All,
>
> Back in March the qla2xxx driver began to use the value in
> cmd->request->nr_hw_segments as a guestimate during the calucation of
> the number of driver-request-queue entries that would be needed to
> fullfill a given command-request. Here's an URL to thread which
> prompted the change:
>
> http://marc.theaimsgroup.com/?l=linux-scsi&m=107940832718154&w=2
>
> Recently we've had a number of problem reports which appear to
> indicate that the value specified within the variable is
> un-initialized and/or set to some bogus value.
>
> Here's the relevant code the driver uses in qla2x00_start_scsi():
>
> /* Calculate the number of request entries needed. */
> req_cnt = (ha->calc_request_entries)(cmd->request->nr_hw_segments);
> if (ha->req_q_cnt < (req_cnt + 2)) {
> cnt = RD_REG_WORD_RELAXED(ISP_REQ_Q_OUT(ha, reg));
> if (ha->req_ring_index < cnt)
> ha->req_q_cnt = cnt - ha->req_ring_index;
> else
> ha->req_q_cnt = ha->request_q_length -
> (ha->req_ring_index - cnt);
> }
> if (ha->req_q_cnt < (req_cnt + 2))
> goto queuing_error;
>
> The 'req_cnt' derived value in several instances is greater than 4000.
>
> So, can an LLDD depend on the value being set to a proper value
> during all I/O submission paths -- BIO as well as IOCTL?
>
> If not, then what should a device driver writer use as an alternative?
Would this by any chance be from request initiated with SG_IO? This
problem should be fixed in 2.6.9-rcX, are you still seeing it?
->nr_hw_segments was not initialized for some paths earlier, so it
contained random crap.
--
Jens Axboe
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: Using scsi_cmd->request->nr_hw_segments within a LLDD...
2004-09-22 6:57 ` Jens Axboe
@ 2004-09-22 15:01 ` Patrick Mansfield
2004-09-22 15:02 ` Jens Axboe
0 siblings, 1 reply; 4+ messages in thread
From: Patrick Mansfield @ 2004-09-22 15:01 UTC (permalink / raw)
To: Jens Axboe; +Cc: Andrew Vasquez, SCSI Mailing List
On Wed, Sep 22, 2004 at 08:57:27AM +0200, Jens Axboe wrote:
> On Tue, Sep 21 2004, Andrew Vasquez wrote:
> Would this by any chance be from request initiated with SG_IO? This
> problem should be fixed in 2.6.9-rcX, are you still seeing it?
>
> ->nr_hw_segments was not initialized for some paths earlier, so it
> contained random crap.
Jens,
What code change is it? I thought it was already in 2.6.8.
-- Patrick Mansfield
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Using scsi_cmd->request->nr_hw_segments within a LLDD...
2004-09-22 15:01 ` Patrick Mansfield
@ 2004-09-22 15:02 ` Jens Axboe
0 siblings, 0 replies; 4+ messages in thread
From: Jens Axboe @ 2004-09-22 15:02 UTC (permalink / raw)
To: Patrick Mansfield; +Cc: Andrew Vasquez, SCSI Mailing List
On Wed, Sep 22 2004, Patrick Mansfield wrote:
> On Wed, Sep 22, 2004 at 08:57:27AM +0200, Jens Axboe wrote:
> > On Tue, Sep 21 2004, Andrew Vasquez wrote:
>
> > Would this by any chance be from request initiated with SG_IO? This
> > problem should be fixed in 2.6.9-rcX, are you still seeing it?
> >
> > ->nr_hw_segments was not initialized for some paths earlier, so it
> > contained random crap.
>
> Jens,
>
> What code change is it? I thought it was already in 2.6.8.
Yes it was already in 2.6.8, I just wasn't sure. It's the
bio_copy_user() stuff that replaces the kmalloc() approach for unaligned
user data.
--
Jens Axboe
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2004-09-22 15:05 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2004-09-21 21:55 Using scsi_cmd->request->nr_hw_segments within a LLDD Andrew Vasquez
2004-09-22 6:57 ` Jens Axboe
2004-09-22 15:01 ` Patrick Mansfield
2004-09-22 15:02 ` Jens Axboe
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