Date: Tue, 15 May 2012 09:25:25 -0700
From: Tejun Heo <tj@kernel.org>
To: Kent Overstreet <koverstreet@google.com>
Cc: linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org,
        dm-devel@redhat.com, agk@redhat.com
Subject: Re: [Bcache v13 02/16] Bio pool freeing
Message-ID: <20120515162525.GC17216@google.com>
References: <cover.1336619038.git.koverstreet@google.com>
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On Wed, May 09, 2012 at 11:08:34PM -0400, Kent Overstreet wrote:
> When you allocate a bio from a bio pool, to free it you have to know
> where it came from; this adds a flag which, if set, means bi_destructor
> is the pointer to the pool and bio_put() can do the right thing.
> 
> This is used in bcache, so we can cleanly use per device bio pools.
> 
> Signed-off-by: Kent Overstreet <koverstreet@google.com>
> ---
>  fs/bio.c                  |    9 +++++++--
>  include/linux/blk_types.h |    2 ++
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/bio.c b/fs/bio.c
> index a965b89..6a967fc 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -417,7 +418,11 @@ void bio_put(struct bio *bio)
>  	 */
>  	if (atomic_dec_and_test(&bio->bi_cnt)) {
>  		bio->bi_next = NULL;
> -		bio->bi_destructor(bio);
> +
> +		if (bio_flagged(bio, BIO_HAS_POOL))
> +			bio_free(bio, (void *) bio->bi_destructor);
> +		else
> +			bio->bi_destructor(bio);

Ummm... this is way too cryptic.  Please just add another field to
bio.

Thanks.

-- 
tejun
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