Re: [PATCH V10 02/19] block: introduce bio_for_each_bvec()

[Omar Sandoval]

On Thu, Nov 15, 2018 at 04:52:49PM +0800, Ming Lei wrote:
> This helper is used for iterating over multi-page bvec for bio
> split & merge code.
> 
> Cc: Dave Chinner <dchinner@xxxxxxxxxx>
> Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Cc: dm-devel@xxxxxxxxxx
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Cc: Shaohua Li <shli@xxxxxxxxxx>
> Cc: linux-raid@xxxxxxxxxxxxxxx
> Cc: linux-erofs@xxxxxxxxxxxxxxxx
> Cc: David Sterba <dsterba@xxxxxxxx>
> Cc: linux-btrfs@xxxxxxxxxxxxxxx
> Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Cc: linux-xfs@xxxxxxxxxxxxxxx
> Cc: Gao Xiang <gaoxiang25@xxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Theodore Ts'o <tytso@xxxxxxx>
> Cc: linux-ext4@xxxxxxxxxxxxxxx
> Cc: Coly Li <colyli@xxxxxxx>
> Cc: linux-bcache@xxxxxxxxxxxxxxx
> Cc: Boaz Harrosh <ooo@xxxxxxxxxxxxxxx>
> Cc: Bob Peterson <rpeterso@xxxxxxxxxx>
> Cc: cluster-devel@xxxxxxxxxx

Reviewed-by: Omar Sandoval <osandov@xxxxxx>

One comment below.

> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
>  include/linux/bio.h  | 34 +++++++++++++++++++++++++++++++---
>  include/linux/bvec.h | 36 ++++++++++++++++++++++++++++++++----
>  2 files changed, 63 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 056fb627edb3..1f0dcf109841 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -76,6 +76,9 @@
>  #define bio_data_dir(bio) \
>  	(op_is_write(bio_op(bio)) ? WRITE : READ)
>  
> +#define bio_iter_mp_iovec(bio, iter)				\
> +	mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))
> +
>  /*
>   * Check whether this bio carries any data or not. A NULL bio is allowed.
>   */
> @@ -135,18 +138,33 @@ static inline bool bio_full(struct bio *bio)
>  #define bio_for_each_segment_all(bvl, bio, i)				\
>  	for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++)
>  
> -static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
> -				    unsigned bytes)
> +static inline void __bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
> +				      unsigned bytes, bool mp)
>  {
>  	iter->bi_sector += bytes >> 9;
>  
>  	if (bio_no_advance_iter(bio))
>  		iter->bi_size -= bytes;
>  	else
> -		bvec_iter_advance(bio->bi_io_vec, iter, bytes);
> +		if (!mp)
> +			bvec_iter_advance(bio->bi_io_vec, iter, bytes);
> +		else
> +			mp_bvec_iter_advance(bio->bi_io_vec, iter, bytes);

if (!foo) {} else {} hurts my brain, please do

		if (mp)
			mp_bvec_iter_advance(bio->bi_io_vec, iter, bytes);
		else
			bvec_iter_advance(bio->bi_io_vec, iter, bytes);