[dm-devel] [PATCH 0/8] dm: request-based dm-multipath

[Hannes Reinecke]

Hi Kiyoshi,

Kiyoshi Ueda wrote:
> Hi Hannes,
> 
> On 2009/01/30 17:05 +0900, Kiyoshi Ueda wrote:
>>>>   o kernel panic occurs by frequent table swapping during heavy I/Os.
>>>>  
>>> That's probably fixed by this patch:
>>>
>>> --- linux-2.6.27/drivers/md/dm.c.orig   2009-01-23 15:59:22.741461315 +0100
>>> +++ linux-2.6.27/drivers/md/dm.c        2009-01-26 09:03:02.787605723 +0100
>>> @@ -714,13 +714,14 @@ static void free_bio_clone(struct reques
>>>         struct dm_rq_target_io *tio = clone->end_io_data;
>>>         struct mapped_device *md = tio->md;
>>>         struct bio *bio;
>>> -       struct dm_clone_bio_info *info;
>>>  
>>>         while ((bio = clone->bio) != NULL) {
>>>                 clone->bio = bio->bi_next;
>>>  
>>> -               info = bio->bi_private;
>>> -               free_bio_info(md, info);
>>> +               if (bio->bi_private) {
>>> +                       struct dm_clone_bio_info *info = bio->bi_private;
>>> +                       free_bio_info(md, info);
>>> +               }
>>>  
>>>                 bio->bi_private = md->bs;
>>>                 bio_put(bio);
>>>
>>> The info field is not necessarily filled here, so we have to check for it
>>> explicitly.
>>>
>>> With these two patches request-based multipathing have survived all stress-tests
>>> so far. Except on mainframe (zfcp), but that's more a driver-related thing.
> 
> My problem was different from that one, and I have fixed my problem.
> 
What was this? Was is something specific to your setup or some within the
request-based multipathing code?
If the latter, I'd be _very_ much interested in seeing the patch. Naturally.

> Do you hit some problem without the patch above?
> If so, that should be a programming bug and we need to fix it.  Otherwise,
> we should be leaking a memory (since all cloned bio should always have
> the dm_clone_bio_info structure in ->bi_private).
> 
Yes, I've found that one later on.
The real problem was in clone_setup_bios(), which might end up calling an
invalid end_io_data pointer. Patch is attached.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare at suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
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