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

[Damien Le Moal]

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@xxxxxxx>
>> ---
>>  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