From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Theodore Ts'o <tytso@mit.edu>,
Omar Sandoval <osandov@fb.com>, Sagi Grimberg <sagi@grimberg.me>,
Dave Chinner <dchinner@redhat.com>,
Kent Overstreet <kent.overstreet@gmail.com>,
Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, Shaohua Li <shli@kernel.org>,
linux-raid@vger.kernel.org, David Sterba <dsterba@suse.com>,
linux-btrfs@vger.kernel.org,
"Darrick J . Wong" <darrick.wong@oracle.com>,
linux-xfs@vger.kernel.org, Gao Xiang <gaoxiang25@huawei.com>,
linux-ext4@vger.kernel.org, Coly Li <colyli@suse.de>,
linux-bcache@vger.kernel.org, Boaz Harrosh <ooo@electrozaur.com>,
Bob Peterson <rpeterso@redhat.com>,
cluster-devel@redhat.com
Subject: Re: [PATCH V11 03/19] block: introduce bio_for_each_bvec()
Date: Thu, 22 Nov 2018 22:57:50 +0800 [thread overview]
Message-ID: <20181122145749.GA22146@ming.t460p> (raw)
In-Reply-To: <20181122103033.GA29418@lst.de>
On Thu, Nov 22, 2018 at 11:30:33AM +0100, Christoph Hellwig wrote:
> Btw, this patch instead of the plain rever might make it a little
> more clear what is going on by skipping the confusing helper altogher
> and operating on the raw bvec array:
>
>
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index e5b975fa0558..926550ce2d21 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -137,24 +137,18 @@ static inline bool bio_full(struct bio *bio)
> 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)
>
> -static inline void __bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
> - unsigned bytes, unsigned max_seg_len)
> +static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
> + unsigned bytes)
> {
> 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, max_seg_len);
> + bvec_iter_advance(bio->bi_io_vec, iter, bytes);
> /* TODO: It is reasonable to complete bio with error here. */
> }
>
> -static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
> - unsigned bytes)
> -{
> - __bio_advance_iter(bio, iter, bytes, PAGE_SIZE);
> -}
> -
> #define __bio_for_each_segment(bvl, bio, iter, start) \
> for (iter = (start); \
> (iter).bi_size && \
> @@ -168,7 +162,7 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
> for (iter = (start); \
> (iter).bi_size && \
> ((bvl = bio_iter_mp_iovec((bio), (iter))), 1); \
> - __bio_advance_iter((bio), &(iter), (bvl).bv_len, BVEC_MAX_LEN))
> + bio_advance_iter((bio), &(iter), (bvl).bv_len))
>
> /* returns one real segment(multi-page bvec) each time */
> #define bio_for_each_bvec(bvl, bio, iter) \
> diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> index cab36d838ed0..7d0f9bdb6f05 100644
> --- a/include/linux/bvec.h
> +++ b/include/linux/bvec.h
> @@ -25,8 +25,6 @@
> #include <linux/errno.h>
> #include <linux/mm.h>
>
> -#define BVEC_MAX_LEN ((unsigned int)-1)
> -
> /*
> * was unsigned short, but we might as well be ready for > 64kB I/O pages
> */
> @@ -102,8 +100,8 @@ struct bvec_iter_all {
> .bv_offset = segment_iter_offset((bvec), (iter)), \
> })
>
> -static inline bool __bvec_iter_advance(const struct bio_vec *bv,
> - struct bvec_iter *iter, unsigned bytes, unsigned max_seg_len)
> +static inline bool bvec_iter_advance(const struct bio_vec *bv,
> + struct bvec_iter *iter, unsigned bytes)
> {
> if (WARN_ONCE(bytes > iter->bi_size,
> "Attempted to advance past end of bvec iter\n")) {
> @@ -112,20 +110,15 @@ static inline bool __bvec_iter_advance(const struct bio_vec *bv,
> }
>
> while (bytes) {
> - unsigned segment_len = segment_iter_len(bv, *iter);
> -
> - if (max_seg_len < BVEC_MAX_LEN)
> - segment_len = min_t(unsigned, segment_len,
> - max_seg_len -
> - bvec_iter_offset(bv, *iter));
> + const struct bio_vec *cur = bv + iter->bi_idx;
> + unsigned len = min3(bytes, iter->bi_size,
> + cur->bv_len - iter->bi_bvec_done);
>
> - segment_len = min(bytes, segment_len);
> -
> - bytes -= segment_len;
> - iter->bi_size -= segment_len;
> - iter->bi_bvec_done += segment_len;
> + bytes -= len;
> + iter->bi_size -= len;
> + iter->bi_bvec_done += len;
>
> - if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
> + if (iter->bi_bvec_done == cur->bv_len) {
> iter->bi_bvec_done = 0;
> iter->bi_idx++;
> }
I'd rather not do the optimization part in this patchset, given it doesn't
belong to this patchset, and it may decrease readability. So I plan to revert
the delta part in V12 first.
Thanks,
Ming
next prev parent reply other threads:[~2018-11-22 14:58 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-21 3:23 [PATCH V11 00/19] block: support multi-page bvec Ming Lei
2018-11-21 3:23 ` [PATCH V11 01/19] block: don't use bio->bi_vcnt to figure out segment number Ming Lei
2018-11-21 3:23 ` [PATCH V11 02/19] block: introduce multi-page bvec helpers Ming Lei
2018-11-21 13:19 ` Christoph Hellwig
2018-11-21 15:06 ` Ming Lei
2018-11-21 16:08 ` Christoph Hellwig
2018-11-22 1:09 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 03/19] block: introduce bio_for_each_bvec() Ming Lei
2018-11-21 13:32 ` Christoph Hellwig
2018-11-21 15:31 ` Ming Lei
2018-11-21 16:10 ` Christoph Hellwig
2018-11-21 17:12 ` Christoph Hellwig
2018-11-22 10:15 ` Ming Lei
2018-11-22 10:23 ` Christoph Hellwig
2018-11-22 10:30 ` Christoph Hellwig
2018-11-22 14:57 ` Ming Lei [this message]
2018-11-22 1:17 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 04/19] block: use bio_for_each_bvec() to compute multi-page bvec count Ming Lei
2018-11-21 3:23 ` [PATCH V11 05/19] block: use bio_for_each_bvec() to map sg Ming Lei
2018-11-21 3:23 ` [PATCH V11 06/19] block: introduce bvec_last_segment() Ming Lei
2018-11-21 3:23 ` [PATCH V11 07/19] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2018-11-22 10:58 ` Christoph Hellwig
2018-11-23 1:48 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 08/19] btrfs: use bvec_last_segment to get bio's last page Ming Lei
2018-11-21 3:23 ` [PATCH V11 09/19] btrfs: move bio_pages_all() to btrfs Ming Lei
2018-11-21 3:23 ` [PATCH V11 10/19] block: loop: pass multi-page bvec to iov_iter Ming Lei
2018-11-21 14:00 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 11/19] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2018-11-21 14:01 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 12/19] block: allow bio_for_each_segment_all() to iterate over multi-page bvec Ming Lei
2018-11-21 14:02 ` Christoph Hellwig
2018-11-22 11:03 ` Christoph Hellwig
2018-11-23 2:19 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 13/19] block: move bounce_clone_bio into bio.c Ming Lei
2018-11-21 3:23 ` [PATCH V11 14/19] block: handle non-cluster bio out of blk_bio_segment_split Ming Lei
2018-11-21 14:33 ` Christoph Hellwig
2018-11-21 15:37 ` Ming Lei
2018-11-21 16:11 ` Christoph Hellwig
2018-11-21 17:46 ` Christoph Hellwig
2018-11-22 9:33 ` Ming Lei
2018-11-22 10:04 ` Christoph Hellwig
2018-11-22 10:26 ` Ming Lei
2018-11-22 10:40 ` Christoph Hellwig
2018-11-22 10:32 ` Ming Lei
2018-11-22 10:41 ` Christoph Hellwig
2018-11-22 10:46 ` Ming Lei
2018-11-22 10:47 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 15/19] block: enable multipage bvecs Ming Lei
2018-11-21 14:55 ` Christoph Hellwig
2018-11-21 15:48 ` Ming Lei
2018-11-21 16:12 ` Christoph Hellwig
2018-11-23 10:50 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 16/19] block: always define BIO_MAX_PAGES as 256 Ming Lei
2018-11-21 3:23 ` [PATCH V11 17/19] block: document usage of bio iterator helpers Ming Lei
2018-11-21 7:45 ` Nikolay Borisov
2018-11-21 14:34 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 18/19] block: kill QUEUE_FLAG_NO_SG_MERGE Ming Lei
2018-11-21 3:23 ` [PATCH V11 19/19] block: kill BLK_MQ_F_SG_MERGE Ming Lei
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