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:
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.
Alan Stern
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