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

Damien Le Moal
2021-01-28T07:31:06Z

On 2021/01/28 16:21, Damien Le Moal wrote:
> 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.

And that also mean that you could remove one argument to bio_new(): combine op
and op_flags into "unsigned int opf"

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

--
Damien Le Moal
Western Digital Research