linux-kernel - Re: [PATCH v2 01/14] block: Generalized bio pool freeing

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Message-ID: <20120524174649.GC27550@redhat.com>
Date:	Thu, 24 May 2012 13:46:49 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org,
	dm-devel@...hat.com, linux-fsdevel@...r.kernel.org, tj@...nel.org,
	axboe@...nel.dk, agk@...hat.com, neilb@...e.de,
	drbd-dev@...ts.linbit.com, bharrosh@...asas.com,
	mpatocka@...hat.com, sage@...dream.net, yehuda@...newdream.net
Subject: Re: [PATCH v2 01/14] block: Generalized bio pool freeing

On Wed, May 23, 2012 at 05:02:38PM -0700, Kent Overstreet wrote:
> With the old code, when you allocate a bio from a bio pool you have to
> implement your own destructor that knows how to find the bio pool the
> bio was originally allocated from.
> 
> This adds a new field to struct bio (bi_pool) and changes
> bio_alloc_bioset() to use it. This makes various bio destructors
> unnecessary, so they're then deleted.
> 

[..]
> @@ -419,7 +406,11 @@ void bio_put(struct bio *bio)
>  	 */
>  	if (atomic_dec_and_test(&bio->bi_cnt)) {
>  		bio->bi_next = NULL;
> -		bio->bi_destructor(bio);
> +
> +		if (bio->bi_pool)
> +			bio_free(bio, bio->bi_pool);
> +		else
> +			bio->bi_destructor(bio);

If you have removed all the users of bi_destructor, then I am wondering that
why are we retaining this field and trying to call into it when bio_pool
is not set?

Thanks
Vivek

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