> -----Original Message-----
> From: Ming Lei [mailto:[email protected]]
> Sent: Friday, December 7, 2018 3:50 PM
> To: Kashyap Desai
> Cc: Bart Van Assche; linux-block; Jens Axboe; linux-scsi; Suganath Prabu
> Subramani; Sreekanth Reddy; Sathya Prakash Veerichetty
> Subject: Re: +AFs-PATCH+AF0- blk-mq: Set request mapping to NULL in
> blk+AF8-mq+AF8-put+AF8-driver+AF8-tag
>
> On Thu, Dec 06, 2018 at 11:15:13AM +0530, Kashyap Desai wrote:
> > >
> > > If the 'tag' passed to scsi_host_find_tag() is valid, I think there
> > > shouldn't have such issue.
> > >
> > > If you want to find outstanding IOs, maybe you can try
> > > blk_mq_queue_tag_busy_iter()
> > > or blk_mq_tagset_busy_iter(), because you may not know if the passed
> > 'tag'
> > > to
> > > scsi_host_find_tag() is valid or not.
> >
> > We tried quick change in mpt3sas driver using blk_mq_tagset_busy_iter
and
> > it returns/callback for valid requests (no stale entries are
returned).
> > Expected.
> > Above two APIs are only for blk-mq. What about non-mq case ? Driver
> > should use scsi_host_find_tag for non-mq and blk_mq_tagset_busy_iter
for
> > blk-mq case ?
>
> But your patch is only for blk-mq, is there same issue on non-mq case?
Problematic part from below function is code path which goes from "
shost_use_blk_mq(shost))".
Non-mq path works fine because every IO completion set bqt->tag_index[tag]
= NULL from blk_queue_end_tag().
I did similar things for mq path in this patch.
static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host
*shost,
int tag)
{
struct request *req = NULL;
if (tag == SCSI_NO_TAG)
return NULL;
if (shost_use_blk_mq(shost)) {
u16 hwq = blk_mq_unique_tag_to_hwq(tag);
if (hwq < shost->tag_set.nr_hw_queues) {
req = blk_mq_tag_to_rq(shost->tag_set.tags[hwq],
blk_mq_unique_tag_to_tag(tag));
}
} else {
req = blk_map_queue_find_tag(shost->bqt, tag);
}
Kashyap
>
> Thanks,
> Ming
