linux-kernel - Re: [PATCH v5 01/12] block: Generalized bio pool freeing

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Message-ID: <20120809002653.GF7262@moria.home.lan>
Date:	Wed, 8 Aug 2012 17:26:53 -0700
From:	Kent Overstreet <koverstreet@...gle.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, axboe@...nel.dk, agk@...hat.com,
	neilb@...e.de, drbd-dev@...ts.linbit.com, vgoyal@...hat.com,
	mpatocka@...hat.com, sage@...dream.net, yehuda@...newdream.net
Subject: Re: [PATCH v5 01/12] block: Generalized bio pool freeing

On Wed, Aug 08, 2012 at 03:25:15PM -0700, Tejun Heo wrote:
> On Mon, Aug 06, 2012 at 03:08:30PM -0700, Kent Overstreet wrote:
> > @@ -422,7 +409,11 @@ void bio_put(struct bio *bio)
> >  	if (atomic_dec_and_test(&bio->bi_cnt)) {
> >  		bio_disassociate_task(bio);
> >  		bio->bi_next = NULL;
> > -		bio->bi_destructor(bio);
> > +
> > +		if (bio->bi_pool)
> > +			bio_free(bio, bio->bi_pool);
> > +		else
> > +			bio->bi_destructor(bio);
> 
> So, this bi_pool overriding caller specified custom bi_destructor is
> rather unusual.  I know why it's like that - the patch series is
> gradually replacing bi_destructor with bi_pool and removes
> bi_destructor eventually, but it would be far better if at least patch
> description says why this is unusual like this.

Ok, I'll stick a comment in there:

	if (atomic_dec_and_test(&bio->bi_cnt)) {
		bio_disassociate_task(bio);
		bio->bi_next = NULL;

		/*
		 * This if statement is temporary - bi_pool is replacing
		 * bi_destructor, but bi_destructor will be taken out in another
		 * patch.
		 */
		if (bio->bi_pool)
			bio_free(bio, bio->bi_pool);
		else
			bio->bi_destructor(bio);
	}

> 
> Thanks.
> 
> -- 
> tejun
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