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

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Message-ID: <20120910204010.GA32310@google.com>
Date:	Mon, 10 Sep 2012 13:40:10 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	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

Hello, Kent.

On Mon, Sep 10, 2012 at 01:24:35PM -0700, Kent Overstreet wrote:
> And at that point, why duplicate that line of code? It doesn't matter that
> much, but IMO a goto retry better labels what's actually going on (it's
> something that's not uncommon in the kernel and if I see a retry label
> in a function I pretty immediately have an idea of what's going on).
> 
> So we could do
> 
> retry:
> p = mempool_alloc(bs->bio_pool, gfp_mask);
> if (!p && gfp_mask != saved_gfp) {
> 	punt_bios_to_rescuer(bs);
> 	gfp_mask = saved_gfp;
> 	goto retry;
> }

Yes, we do retry loops if that makes the code simpler.  Doing that to
save one extra alloc call, I don't think so.

Thanks.

-- 
tejun
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