[dm-devel] [PATCH 4/7] dm mpath: remove process_queued_ios()
Hannes Reinecke
hare at suse.de
Tue Feb 4 09:08:56 UTC 2014
On 02/04/2014 09:55 AM, Junichi Nomura wrote:
> On 02/04/14 17:18, Hannes Reinecke wrote:
>>>> @@ -1591,8 +1563,17 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
>>> ...
>>>> + if (m->current_pg && m->pg_init_required)
>>>> + __pg_init_all_paths(m, 0);
>>>> + spin_unlock_irqrestore(&m->lock, flags);
>>>> + dm_table_run_md_queue_async(m->ti->table);
>>>> + }
>>>
>>> What happens if "!m->current_pg && m->pg_init_required"?
>>>
>> >From the current logic it means that no valid pg was found, so
>> calling pg_init would be pointless.
>> We're calling __choose_pgpath() before that, so if that returns
>> with current_pg == NULL all paths are down, and calling
>> pg_init would be pointless.
>>
>> But I think I see to have pg_init_required handling cleared up;
>> I'll be doing a patch to unset it at the start of __choose_pgpath(),
>> this we we can be sure that it'll be set correctly.
>
> I think it is possible that __choose_pgpath() being called twice
> before pg_init_required is checked.
>
> For example,
>
> multipath_ioctl()
> __choose_pgpath()
> clear pg_init_required
> select a new pg
> __switch_pg()
> set pg_init_required
>
> map_io()
> __choose_pgpath()
> clear pg_init_required
> select the same pg
> (pg_init_required is not set)
> ...
>
But why should 'map_io' calling __choose_pgpath()?
Either __choose_path() from ioctl was able to set ->current_pg
(in which case __choose_pgpath() wouldn't be called in map_io)
or it was not, in which case pg_init_required would need to be reset
during __choose_pgpath() when called from map_io().
Am I missing something?
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare at suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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