On 07/12/2013 12:00 PM, Ren Mingxin wrote:
> Hi, Hannes:
> 
> On 07/12/2013 02:09 PM, Hannes Reinecke wrote:
>> On 07/12/2013 06:14 AM, Ren Mingxin wrote:
>>> On 07/01/2013 10:24 PM, Hannes Reinecke wrote:
>>>> With the original SCSI EH I got:
>>>> # time dd if=/dev/zero of=/dev/dm-2 bs=4k count=4k oflag=direct
>>>> 4096+0 records in
>>>> 4096+0 records out
>>>> 16777216 bytes (17 MB) copied, 142.652 s, 118 kB/s
>>>>
>>>> real    2m22.657s
>>>> user    0m0.013s
>>>> sys    0m0.145s
>>>>
>>>> With this patchset I got:
>>>> # time dd if=/dev/zero of=/dev/dm-2 bs=4k count=4k oflag=direct
>>>> 4096+0 records in
>>>> 4096+0 records out
>>>> 16777216 bytes (17 MB) copied, 52.1579 s, 322 kB/s
>>>>
>>>> real    0m52.163s
>>>> user    0m0.012s
>>>> sys    0m0.145s
>>>>
>>>> Test was to disable RSCN on the target port, disable the
>>>> target port, and then start the 'dd' command as indicated.
>>>
>>> Do you mean disabling RSCN/port is enough? I'm afraid I couldn't
>>> reproduce the problem by your steps. Both with and without your
>>> patchset are the same 'dd' result: 27s. Please let me know where I
>>> neglected or mistook:
>>>
>>> 1) I made a dm-multipath target 'dm-0' whose grouping policy was
>>>     failover;
>>> 2) Disable RSCN/port via brocade fc switch:
>>>     SW300:root>  portcfg rscnsupr 15 --enable; portDisable 15
>>> 3) Start the 'dd' command:
>>>     # time dd if=/dev/zero of=/dev/dm-0 bs=4k count=4k oflag=direct
>>>     dd: writing `/dev/sde': Input/output error
>>>     1+0 records in
>>>     0+0 records out
>>>     0 bytes (0 B) copied, 27.8588 s, 0.0 kB/s
>>>
>>>     real    0m27.860s
>>>     user    0m0.001s
>>>     sys     0m0.000s
>>
>> You are aware that you have to disable RSCNs on the _target_ port,
>> right?
>> Disabling RSCNs on the _initiator_ ports is a well-tested case, and
>> the one which actually makes sense (and is even implemented in
>> QLogic switches).
>> Disabling RSCNs for the _target_ port, OTOH, has a very questionable
>> nature (hence QLogic switches don't even allow you to do this).
> 
> You're right. By disabling RSCNs on target port, I've reproduced this
> problem. Thank you so much. But I've encountered the bug I said
> before. I'll test again with your new patchset once you send.
> 

Could you check with the attached patch? That should convert it to
delayed_work and avoid this issue.

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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