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

[Chaitanya Kulkarni <Chaitanya.Kulkarni@xxxxxxx>]

On 1/27/21 11:21 PM, 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.
true, I'll add that check.
> > +
> > +	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.
true, will do.
> > +
> > +	return bio;
> > +}
> >  
> >  #endif /* __LINUX_BIO_H */

Thanks for the comments Damien.