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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 07:27:21 +0000
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On 2021/01/28 16:21, Damien Le Moal wrote:=0A=
> 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 blo=
ck_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, =
struct 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 s=
ector,=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 s=
hould=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=
And that also mean that you could remove one argument to bio_new(): combine=
 op=0A=
and op_flags into "unsigned int opf"=0A=
=0A=
> =0A=
>> +=0A=
>> +	return bio;=0A=
>> +}=0A=
>>  =0A=
>>  #endif /* __LINUX_BIO_H */=0A=
>>=0A=
> =0A=
> =0A=
=0A=
=0A=
-- =0A=
Damien Le Moal=0A=
Western Digital Research=0A=