On Thu, 2014-03-20 at 15:48 -0400, Alan Stern wrote:
> On Thu, 20 Mar 2014, James Bottomley wrote:
>
> > On Thu, 2014-03-20 at 12:34 -0400, Alan Stern wrote:
> > > On Thu, 20 Mar 2014, James Bottomley wrote:
> > >
> > > > OK, so I think we have three things to do
> > > >
> > > > 1. Investigate SCSI and fix it's abort state problem that's causing
> > > > it not to send the abort second time around
> > > > 2. Fix usb-storage to fail a reset it can't do (i.e. device reset
> > > > with outstanding commands)
> > > > 3. Find out why we're sending a spurious request sense.
> > > >
> > > > I can look at 1 and 3 if you want to take 2.
> > >
> > > It's a deal! Thanks for your help.
> >
> > And this looks to be 3: a bug in the way we attach sense data to
> > commands (we shouldn't look for attached sense if the device error code
> > didn't imply there would be any).
> >
> > James
> >
> > ---
> >
> > diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> > index 771c16b..d020149 100644
> > --- a/drivers/scsi/scsi_error.c
> > +++ b/drivers/scsi/scsi_error.c
> > @@ -1157,6 +1157,15 @@ int scsi_eh_get_sense(struct list_head *work_q,
> > __func__));
> > break;
> > }
> > + if (status_byte(scmd->result) != CHECK_CONDITION)
> > + /*
> > + * don't request sense if there's no check condition
> > + * status because the error we're processing isn't one
> > + * that has a sense code (and some devices get
> > + * confused by sense requests out of the blue)
> > + */
> > + continue;
> > +
> > SCSI_LOG_ERROR_RECOVERY(2, scmd_printk(KERN_INFO, scmd,
> > "%s: requesting sense\n",
> > current->comm));
>
> I tried this patch first, because fixing the earlier bug would mask
> this one.
>
> The patch sort of worked. But the first time I tried it, it failed in
> a rather amusing way. While the second retry was running and hung,
> scmd->result _was_ equal to CHECK_CONDITION -- because that was the
> result from the _first_ retry, and it had never gotten cleared!
>
> scmd->result needs to be set to 0 before the queuecommand callback is
> invoked. I ended up adding this to your patch, and then it worked
> perfectly:
Wow, the stale data bugs are just crawling out of the code. Thanks for
checking.
>
> Index: usb-3.14/drivers/scsi/scsi_error.c
> ===================================================================
> --- usb-3.14.orig/drivers/scsi/scsi_error.c
> +++ usb-3.14/drivers/scsi/scsi_error.c
> @@ -924,6 +924,7 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd
> memset(scmd->cmnd, 0, BLK_MAX_CDB);
> memset(&scmd->sdb, 0, sizeof(scmd->sdb));
> scmd->request->next_rq = NULL;
> + scmd->result = 0;
>
> if (sense_bytes) {
> scmd->sdb.length = min_t(unsigned, SCSI_SENSE_BUFFERSIZE,
> Index: usb-3.14/drivers/scsi/scsi_lib.c
> ===================================================================
> --- usb-3.14.orig/drivers/scsi/scsi_lib.c
> +++ usb-3.14/drivers/scsi/scsi_lib.c
> @@ -159,6 +159,7 @@ static void __scsi_queue_insert(struct s
> * lock such that the kblockd_schedule_work() call happens
> * before blk_cleanup_queue() finishes.
> */
> + cmd->result = 0;
> spin_lock_irqsave(q->queue_lock, flags);
> blk_requeue_request(q, cmd->request);
> kblockd_schedule_work(q, &device->requeue_work);
>
>
> Maybe only the second one is necessary, but it seemed best to be
> consistent.
Thanks, I'll add this one to the list as well and see if we can get it
into the merge window. I take it you'd like a cc to stable on these
three?
James
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