Re: [PATCH V10 12/19] block: allow bio_for_each_segment_all() to iterate over multi-page bvec

Omar Sandoval
2018-11-16T01:22:51Z

On Thu, Nov 15, 2018 at 04:52:59PM +0800, Ming Lei wrote:
> This patch introduces one extra iterator variable to bio_for_each_segment_all(),
> then we can allow bio_for_each_segment_all() to iterate over multi-page bvec.
>
> Given it is just one mechannical & simple change on all bio_for_each_segment_all()
> users, this patch does tree-wide change in one single patch, so that we can
> avoid to use a temporary helper for this conversion.
>
> Cc: Dave Chinner <dchinner@redhat.com>
> Cc: Kent Overstreet <kent.overstreet@gmail.com>
> Cc: linux-fsdevel@vger.kernel.org
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: linux-raid@vger.kernel.org
> Cc: linux-erofs@lists.ozlabs.org
> Cc: linux-btrfs@vger.kernel.org
> Cc: David Sterba <dsterba@suse.com>
> Cc: Darrick J. Wong <darrick.wong@oracle.com>
> Cc: Gao Xiang <gaoxiang25@huawei.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Theodore Ts'o <tytso@mit.edu>
> Cc: linux-ext4@vger.kernel.org
> Cc: Coly Li <colyli@suse.de>
> Cc: linux-bcache@vger.kernel.org
> Cc: Boaz Harrosh <ooo@electrozaur.com>
> Cc: Bob Peterson <rpeterso@redhat.com>
> Cc: cluster-devel@redhat.com
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> block/bio.c | 27 ++++++++++++++++++---------
> block/blk-zoned.c | 1 +
> block/bounce.c | 6 ++++--
> drivers/md/bcache/btree.c | 3 ++-
> drivers/md/dm-crypt.c | 3 ++-
> drivers/md/raid1.c | 3 ++-
> drivers/staging/erofs/data.c | 3 ++-
> drivers/staging/erofs/unzip_vle.c | 3 ++-
> fs/block_dev.c | 6 ++++--
> fs/btrfs/compression.c | 3 ++-
> fs/btrfs/disk-io.c | 3 ++-
> fs/btrfs/extent_io.c | 12 ++++++++----
> fs/btrfs/inode.c | 6 ++++--
> fs/btrfs/raid56.c | 3 ++-
> fs/crypto/bio.c | 3 ++-
> fs/direct-io.c | 4 +++-
> fs/exofs/ore.c | 3 ++-
> fs/exofs/ore_raid.c | 3 ++-
> fs/ext4/page-io.c | 3 ++-
> fs/ext4/readpage.c | 3 ++-
> fs/f2fs/data.c | 9 ++++++---
> fs/gfs2/lops.c | 6 ++++--
> fs/gfs2/meta_io.c | 3 ++-
> fs/iomap.c | 6 ++++--
> fs/mpage.c | 3 ++-
> fs/xfs/xfs_aops.c | 5 +++--
> include/linux/bio.h | 11 +++++++++--
> include/linux/bvec.h | 31 +++++++++++++++++++++++++++++++
> 28 files changed, 129 insertions(+), 46 deletions(-)
>

[snip]

> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 3496c816946e..1a2430a8b89d 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -131,12 +131,19 @@ static inline bool bio_full(struct bio *bio)
> return bio->bi_vcnt >= bio->bi_max_vecs;
> }
>
> +#define bvec_for_each_segment(bv, bvl, i, iter_all) \
> + for (bv = bvec_init_iter_all(&iter_all); \
> + (iter_all.done < (bvl)->bv_len) && \
> + ((bvec_next_segment((bvl), &iter_all)), 1); \

The parentheses around (bvec_next_segment((bvl), &iter_all)) are
unnecessary.

> + iter_all.done += bv->bv_len, i += 1)
> +
> /*
> * drivers should _never_ use the all version - the bio may have been split
> * before it got to the driver and the driver won't own all of it
> */
> -#define bio_for_each_segment_all(bvl, bio, i) \
> - for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++)
> +#define bio_for_each_segment_all(bvl, bio, i, iter_all) \
> + for (i = 0, iter_all.idx = 0; iter_all.idx < (bio)->bi_vcnt; iter_all.idx++) \
> + bvec_for_each_segment(bvl, &((bio)->bi_io_vec[iter_all.idx]), i, iter_all)

Would it be possible to move i into iter_all to streamline this a bit?

> static inline void __bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
> unsigned bytes, bool mp)
> diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> index 01616a0b6220..02f26d2b59ad 100644
> --- a/include/linux/bvec.h
> +++ b/include/linux/bvec.h
> @@ -82,6 +82,12 @@ struct bvec_iter {
> current bvec */
> };
>
> +struct bvec_iter_all {
> + struct bio_vec bv;
> + int idx;
> + unsigned done;
> +};
> +
> /*
> * various member access, note that bio_data should of course not be used
> * on highmem page vectors
> @@ -216,6 +222,31 @@ static inline bool mp_bvec_iter_advance(const struct bio_vec *bv,
> .bi_bvec_done = 0, \
> }
>
> +static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
> +{
> + iter_all->bv.bv_page = NULL;
> + iter_all->done = 0;
> +
> + return &iter_all->bv;
> +}
> +
> +/* used for chunk_for_each_segment */
> +static inline void bvec_next_segment(const struct bio_vec *bvec,
> + struct bvec_iter_all *iter_all)

Indentation.

> +{
> + struct bio_vec *bv = &iter_all->bv;
> +
> + if (bv->bv_page) {
> + bv->bv_page += 1;
> + bv->bv_offset = 0;
> + } else {
> + bv->bv_page = bvec->bv_page;
> + bv->bv_offset = bvec->bv_offset;
> + }
> + bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
> + bvec->bv_len - iter_all->done);

Indentation.

> +}
> +
> /*
> * Get the last singlepage segment from the multipage bvec and store it
> * in @seg
> --
> 2.9.5
>