Re: [RFC PATCH 02/34] block: introduce and use bio_new

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2021/01/28 16:12, Chaitanya Kulkarni wrote:
> Introduce bio_new() helper and use it in blk-lib.c to allocate and
> initialize various non-optional or semi-optional members of the bio
> along with bio allocation done with bio_alloc(). Here we also calmp the
> max_bvecs for bio with BIO_MAX_PAGES before we pass to bio_alloc().
> 
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
> ---
>  block/blk-lib.c     |  6 +-----
>  include/linux/bio.h | 25 +++++++++++++++++++++++++
>  2 files changed, 26 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-lib.c b/block/blk-lib.c
> index fb486a0bdb58..ec29415f00dd 100644
> --- a/block/blk-lib.c
> +++ b/block/blk-lib.c
> @@ -14,17 +14,13 @@ struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
>  			sector_t sect, unsigned op, unsigned opf,
>  			unsigned int nr_pages, gfp_t gfp)
>  {
> -	struct bio *new = bio_alloc(gfp, nr_pages);
> +	struct bio *new = bio_new(bdev, sect, op, opf, gfp, nr_pages);
>  
>  	if (bio) {
>  		bio_chain(bio, new);
>  		submit_bio(bio);
>  	}
>  
> -	new->bi_iter.bi_sector = sect;
> -	bio_set_dev(new, bdev);
> -	bio_set_op_attrs(new, op, opf);
> -
>  	return new;
>  }
>  
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index c74857cf1252..2a09ba100546 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -826,5 +826,30 @@ static inline void bio_set_polled(struct bio *bio, struct kiocb *kiocb)
>  	if (!is_sync_kiocb(kiocb))
>  		bio->bi_opf |= REQ_NOWAIT;
>  }
> +/**
> + * bio_new -	allcate and initialize new bio
> + * @bdev:	blockdev to issue discard for
> + * @sector:	start sector
> + * @op:		REQ_OP_XXX from enum req_opf
> + * @op_flags:	REQ_XXX from enum req_flag_bits
> + * @max_bvecs:	maximum bvec to be allocated for this bio
> + * @gfp_mask:	memory allocation flags (for bio_alloc)
> + *
> + * Description:
> + *    Allocates, initializes common members, and returns a new bio.
> + */
> +static inline struct bio *bio_new(struct block_device *bdev, sector_t sector,
> +				  unsigned int op, unsigned int op_flags,
> +				  unsigned int max_bvecs, gfp_t gfp_mask)
> +{
> +	unsigned nr_bvec = clamp_t(unsigned int, max_bvecs, 0, BIO_MAX_PAGES);
> +	struct bio *bio = bio_alloc(gfp_mask, nr_bvec);

I think that depending on the gfp_mask passed, bio can be NULL. So this should
be checked.

> +
> +	bio_set_dev(bio, bdev);
> +	bio->bi_iter.bi_sector = sector;
> +	bio_set_op_attrs(bio, op, op_flags);

This function is obsolete. Open code this.

> +
> +	return bio;
> +}
>  
>  #endif /* __LINUX_BIO_H */
> 


-- 
Damien Le Moal
Western Digital Research