Re: SCSI regression in 4.11

[Hannes Reinecke <hare@suse.de>]

On 03/02/2017 02:40 AM, Stephen Hemminger wrote:
> On Thu, 2 Mar 2017 01:56:15 +0100
> Christoph Hellwig <hch@lst.de> wrote:
>
>> On Thu, Mar 02, 2017 at 01:01:35AM +0100, Christoph Hellwig wrote:
>>> On Wed, Mar 01, 2017 at 07:54:12AM -0800, Stephen Hemminger wrote:
>>>>> 	http://git.infradead.org/users/hch/block.git/commitdiff/148cff67b401e2229c076c0ea418712654be77e4
>>>>
>>>> It appears that is already in the code I am testing in linux-next...
>>>
>>> It's in -next now, but it wasn't at the time you reported the bug.
>>>
>>> And it would sortof explain the bug if the INQUIRY data is correct
>>> in the scatterlist, but we ignore it, given that scsi_probe_lun
>>> ignores the result based on sense data.
>>>
>>> Can you check what happens with the horrible hack below:
>>
>> Strike that - we're checking result later, so this can't be the case.
>>
>> Now the other interesting thing is the memset in __scsi_exectute,
>> which looks very suspicious.  Try the following please:
>>
>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>> index 3e32dc954c3c..22f4fb550561 100644
>> --- a/drivers/scsi/scsi_lib.c
>> +++ b/drivers/scsi/scsi_lib.c
>> @@ -253,7 +253,8 @@ static int __scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
>>  	 * and prevent security leaks by zeroing out the excess data.
>>  	 */
>>  	if (unlikely(rq->resid_len > 0 && rq->resid_len <= bufflen))
>> -		memset(buffer + (bufflen - rq->resid_len), 0, rq->resid_len);
>> +//		memset(buffer + (bufflen - rq->resid_len), 0, rq->resid_len);
>> +		printk_ratelimited("%s: got resid %d\n", __func__, rq->resid_len);
>>
>>  	if (resid)
>>  		*resid = rq->resid_len;
>
>
> Still fails but does print resid on some of the later INQUIRY commands (not the initial one).
>
Can you test what happens if you blank out the storvsc_drv workaround:

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 585e54f..c36f42d 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1060,13 +1060,13 @@ static void storvsc_on_io_completion(struct 
storvsc_device *stor_device,
          * We do this so we can distinguish truly fatal failues
          * (srb status == 0x4) and off-line the device in that case.
          */
-
+#if 0
         if ((stor_pkt->vm_srb.cdb[0] == INQUIRY) ||
            (stor_pkt->vm_srb.cdb[0] == MODE_SENSE)) {
                 vstor_packet->vm_srb.scsi_status = 0;
                 vstor_packet->vm_srb.srb_status = SRB_STATUS_SUCCESS;
         }
-
+#endif

         /* Copy over the status...etc */
         stor_pkt->vm_srb.scsi_status = vstor_packet->vm_srb.scsi_status;

It might thappen that we're fail to interpret the 'Device not present' 
status correctly (which will happen for non-connected DVDs) causing the 
SCSI stack to make incorrect decisions later on.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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