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From:   Damien Le Moal <Damien.LeMoal@wdc.com>
To:     Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
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Subject: Re: [RFC PATCH 02/34] block: introduce and use bio_new
Thread-Topic: [RFC PATCH 02/34] block: introduce and use bio_new
Thread-Index: AQHW9UTnP+XqlvwCeEC+5iodtWSeNA==
Date:   Thu, 28 Jan 2021 07:21:42 +0000
Message-ID: <BL0PR04MB6514C554B4AC96866BC1B16FE7BA9@BL0PR04MB6514.namprd04.prod.outlook.com>
References: <20210128071133.60335-1-chaitanya.kulkarni@wdc.com>
 <20210128071133.60335-3-chaitanya.kulkarni@wdc.com>
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On 2021/01/28 16:12, Chaitanya Kulkarni wrote:=0A=
> Introduce bio_new() helper and use it in blk-lib.c to allocate and=0A=
> initialize various non-optional or semi-optional members of the bio=0A=
> along with bio allocation done with bio_alloc(). Here we also calmp the=
=0A=
> max_bvecs for bio with BIO_MAX_PAGES before we pass to bio_alloc().=0A=
> =0A=
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>=0A=
> ---=0A=
>  block/blk-lib.c     |  6 +-----=0A=
>  include/linux/bio.h | 25 +++++++++++++++++++++++++=0A=
>  2 files changed, 26 insertions(+), 5 deletions(-)=0A=
> =0A=
> diff --git a/block/blk-lib.c b/block/blk-lib.c=0A=
> index fb486a0bdb58..ec29415f00dd 100644=0A=
> --- a/block/blk-lib.c=0A=
> +++ b/block/blk-lib.c=0A=
> @@ -14,17 +14,13 @@ struct bio *blk_next_bio(struct bio *bio, struct bloc=
k_device *bdev,=0A=
>  			sector_t sect, unsigned op, unsigned opf,=0A=
>  			unsigned int nr_pages, gfp_t gfp)=0A=
>  {=0A=
> -	struct bio *new =3D bio_alloc(gfp, nr_pages);=0A=
> +	struct bio *new =3D bio_new(bdev, sect, op, opf, gfp, nr_pages);=0A=
>  =0A=
>  	if (bio) {=0A=
>  		bio_chain(bio, new);=0A=
>  		submit_bio(bio);=0A=
>  	}=0A=
>  =0A=
> -	new->bi_iter.bi_sector =3D sect;=0A=
> -	bio_set_dev(new, bdev);=0A=
> -	bio_set_op_attrs(new, op, opf);=0A=
> -=0A=
>  	return new;=0A=
>  }=0A=
>  =0A=
> diff --git a/include/linux/bio.h b/include/linux/bio.h=0A=
> index c74857cf1252..2a09ba100546 100644=0A=
> --- a/include/linux/bio.h=0A=
> +++ b/include/linux/bio.h=0A=
> @@ -826,5 +826,30 @@ static inline void bio_set_polled(struct bio *bio, s=
truct kiocb *kiocb)=0A=
>  	if (!is_sync_kiocb(kiocb))=0A=
>  		bio->bi_opf |=3D REQ_NOWAIT;=0A=
>  }=0A=
> +/**=0A=
> + * bio_new -	allcate and initialize new bio=0A=
> + * @bdev:	blockdev to issue discard for=0A=
> + * @sector:	start sector=0A=
> + * @op:		REQ_OP_XXX from enum req_opf=0A=
> + * @op_flags:	REQ_XXX from enum req_flag_bits=0A=
> + * @max_bvecs:	maximum bvec to be allocated for this bio=0A=
> + * @gfp_mask:	memory allocation flags (for bio_alloc)=0A=
> + *=0A=
> + * Description:=0A=
> + *    Allocates, initializes common members, and returns a new bio.=0A=
> + */=0A=
> +static inline struct bio *bio_new(struct block_device *bdev, sector_t se=
ctor,=0A=
> +				  unsigned int op, unsigned int op_flags,=0A=
> +				  unsigned int max_bvecs, gfp_t gfp_mask)=0A=
> +{=0A=
> +	unsigned nr_bvec =3D clamp_t(unsigned int, max_bvecs, 0, BIO_MAX_PAGES)=
;=0A=
> +	struct bio *bio =3D bio_alloc(gfp_mask, nr_bvec);=0A=
=0A=
I think that depending on the gfp_mask passed, bio can be NULL. So this sho=
uld=0A=
be checked.=0A=
=0A=
> +=0A=
> +	bio_set_dev(bio, bdev);=0A=
> +	bio->bi_iter.bi_sector =3D sector;=0A=
> +	bio_set_op_attrs(bio, op, op_flags);=0A=
=0A=
This function is obsolete. Open code this.=0A=
=0A=
> +=0A=
> +	return bio;=0A=
> +}=0A=
>  =0A=
>  #endif /* __LINUX_BIO_H */=0A=
> =0A=
=0A=
=0A=
-- =0A=
Damien Le Moal=0A=
Western Digital Research=0A=