linux-kernel - Re: [PATCH 2/2] block: Avoid deadlocks with bio allocation by stacking drivers

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Date:	Tue, 11 Sep 2012 11:58:05 -0700
From:	Muthu Kumar <muthu.lkml@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Kent Overstreet <koverstreet@...gle.com>,
	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, axboe@...nel.dk,
	Vivek Goyal <vgoyal@...hat.com>,
	Mikulas Patocka <mpatocka@...hat.com>, bharrosh@...asas.com,
	david@...morbit.com
Subject: Re: [PATCH 2/2] block: Avoid deadlocks with bio allocation by
 stacking drivers

On Tue, Sep 11, 2012 at 11:45 AM, Tejun Heo <tj@...nel.org> wrote:
> Hello,
>
> On Tue, Sep 11, 2012 at 11:36:28AM -0700, Muthu Kumar wrote:
>> Does this preserve the CPU from which the bio was submitted
>> originally. Not familiar with cmwq, may be Tejun can clarify.
>>
>> Tejun - the question is, do we honor the rq_affinity with the above
>> rescue worker implementation?
>
> The work item would run from the same CPU but there isn't any
> mechanism to keep track of the issuing CPU if there are multiple bios
> to be rescued.  Isn't rq_affinity an optimization hint?  If so, I
> don't think it matters here.
>

Thanks... Just worried about performance impact.

Kent - Anything to validate that the performance is not impacted would
be really good. Otherwise, the patch looks great.

Feel free to add:

Reviewed-by: Muthukumar Ratty <muthur@...il.com>


Regards,
Muthu


> Thanks.
>
> --
> tejun
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