Re: [PATCH 01/12] block: bio: pass bvec table to bio_init()

From: Christoph Hellwig
Date: Sat Nov 12 2016 - 12:59:58 EST


On Fri, Nov 11, 2016 at 08:05:29PM +0800, Ming Lei wrote:
> Some drivers often use external bvec table, so introduce
> this helper for this case. It is always safe to access the
> bio->bi_io_vec in this way for this case.
>
> After converting to this usage, it will becomes a bit easier
> to evaluate the remaining direct access to bio->bi_io_vec,
> so it can help to prepare for the following multipage bvec
> support.
>
> Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
> ---
> block/bio.c | 8 ++++++--
> drivers/block/floppy.c | 3 +--
> drivers/md/bcache/io.c | 4 +---
> drivers/md/bcache/journal.c | 4 +---
> drivers/md/bcache/movinggc.c | 6 ++----
> drivers/md/bcache/request.c | 2 +-
> drivers/md/bcache/super.c | 12 +++---------
> drivers/md/bcache/writeback.c | 5 ++---
> drivers/md/dm-bufio.c | 4 +---
> drivers/md/dm.c | 2 +-
> drivers/md/multipath.c | 2 +-
> drivers/md/raid5-cache.c | 2 +-
> drivers/md/raid5.c | 9 ++-------
> drivers/nvme/target/io-cmd.c | 4 +---
> fs/logfs/dev_bdev.c | 4 +---
> include/linux/bio.h | 3 ++-
> 16 files changed, 27 insertions(+), 47 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 2cf6ebabc68c..de257ced69b1 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -270,11 +270,15 @@ static void bio_free(struct bio *bio)
> }
> }
>
> -void bio_init(struct bio *bio)
> +void bio_init(struct bio *bio, struct bio_vec *table,
> + unsigned short max_vecs)
> {
> memset(bio, 0, sizeof(*bio));
> atomic_set(&bio->__bi_remaining, 1);
> atomic_set(&bio->__bi_cnt, 1);
> +
> + bio->bi_io_vec = table;
> + bio->bi_max_vecs = max_vecs;
> }
> EXPORT_SYMBOL(bio_init);
>
> @@ -480,7 +484,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
> return NULL;
>
> bio = p + front_pad;
> - bio_init(bio);
> + bio_init(bio, NULL, 0);
>
> if (nr_iovecs > inline_vecs) {
> unsigned long idx = 0;
> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index e3d8e4ced4a2..6a3ff2b2e3ae 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -3806,8 +3806,7 @@ static int __floppy_read_block_0(struct block_device *bdev, int drive)
>
> cbdata.drive = drive;
>
> - bio_init(&bio);
> - bio.bi_io_vec = &bio_vec;
> + bio_init(&bio, &bio_vec, 1);
> bio_vec.bv_page = page;
> bio_vec.bv_len = size;
> bio_vec.bv_offset = 0;
> diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
> index e97b0acf7b8d..db45a88c0ce9 100644
> --- a/drivers/md/bcache/io.c
> +++ b/drivers/md/bcache/io.c
> @@ -24,9 +24,7 @@ struct bio *bch_bbio_alloc(struct cache_set *c)
> struct bbio *b = mempool_alloc(c->bio_meta, GFP_NOIO);
> struct bio *bio = &b->bio;
>
> - bio_init(bio);
> - bio->bi_max_vecs = bucket_pages(c);
> - bio->bi_io_vec = bio->bi_inline_vecs;
> + bio_init(bio, bio->bi_inline_vecs, bucket_pages(c));
>
> return bio;
> }
> diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
> index 6925023e12d4..1198e53d5670 100644
> --- a/drivers/md/bcache/journal.c
> +++ b/drivers/md/bcache/journal.c
> @@ -448,13 +448,11 @@ static void do_journal_discard(struct cache *ca)
>
> atomic_set(&ja->discard_in_flight, DISCARD_IN_FLIGHT);
>
> - bio_init(bio);
> + bio_init(bio, bio->bi_inline_vecs, 1);
> bio_set_op_attrs(bio, REQ_OP_DISCARD, 0);
> bio->bi_iter.bi_sector = bucket_to_sector(ca->set,
> ca->sb.d[ja->discard_idx]);
> bio->bi_bdev = ca->bdev;
> - bio->bi_max_vecs = 1;
> - bio->bi_io_vec = bio->bi_inline_vecs;
> bio->bi_iter.bi_size = bucket_bytes(ca);
> bio->bi_end_io = journal_discard_endio;
>
> diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c
> index 5c4bddecfaf0..13b8a907006d 100644
> --- a/drivers/md/bcache/movinggc.c
> +++ b/drivers/md/bcache/movinggc.c
> @@ -77,15 +77,13 @@ static void moving_init(struct moving_io *io)
> {
> struct bio *bio = &io->bio.bio;
>
> - bio_init(bio);
> + bio_init(bio, bio->bi_inline_vecs,
> + DIV_ROUND_UP(KEY_SIZE(&io->w->key), PAGE_SECTORS));
> bio_get(bio);
> bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
>
> bio->bi_iter.bi_size = KEY_SIZE(&io->w->key) << 9;
> - bio->bi_max_vecs = DIV_ROUND_UP(KEY_SIZE(&io->w->key),
> - PAGE_SECTORS);
> bio->bi_private = &io->cl;
> - bio->bi_io_vec = bio->bi_inline_vecs;
> bch_bio_map(bio, NULL);
> }
>
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index 0d99b5f4b3e6..f49c5417527d 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -623,7 +623,7 @@ static void do_bio_hook(struct search *s, struct bio *orig_bio)
> {
> struct bio *bio = &s->bio.bio;
>
> - bio_init(bio);
> + bio_init(bio, NULL, 0);
> __bio_clone_fast(bio, orig_bio);

We have this pattern multiple times, and it almost screams for a helper.
But I think we're better off letting your patch go in as-is and sort
that out later instead of delaying it.

Otherwise this looks fine:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>