Re: [dm-devel] [Bcache v13 02/16] Bio pool freeing

[Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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.

Ok, that will explain BIO_HAS_POOL flag.  Why to replace
bio_has_allocated_vec() with BIO_HAS_VEC flag?

Thanks
Vivek

> 
> Signed-off-by: Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> ---
>  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
> @@ -235,7 +235,7 @@ void bio_free(struct bio *bio, struct bio_set *bs)
>  {
>  	void *p;
>  
> -	if (bio_has_allocated_vec(bio))
> +	if (bio_flagged(bio, BIO_HAS_VEC))
>  		bvec_free_bs(bs, bio->bi_io_vec, BIO_POOL_IDX(bio));
>  
>  	if (bio_integrity(bio))
> @@ -301,6 +301,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
>  			goto err_free;
>  
>  		nr_iovecs = bvec_nr_vecs(idx);
> +		bio->bi_flags |= 1 << BIO_HAS_VEC;
>  	}
>  out_set:
>  	bio->bi_flags |= idx << BIO_POOL_OFFSET;
> @@ -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);
>  	}
>  }
>  EXPORT_SYMBOL(bio_put);
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 4053cbd..a0be8b3 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -95,6 +95,8 @@ struct bio {
>  #define BIO_FS_INTEGRITY 9	/* fs owns integrity data, not block layer */
>  #define BIO_QUIET	10	/* Make BIO Quiet */
>  #define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
> +#define BIO_HAS_POOL	12	/* bi_destructor points to bio_pool */
> +#define BIO_HAS_VEC	13	/* bio_free() should free bvec */
>  #define bio_flagged(bio, flag)	((bio)->bi_flags & (1 << (flag)))
>  
>  /*
> -- 
> 1.7.9.rc2
> 
> --
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