From: Omar Sandoval <osandov@osandov.com>
To: Ming Lei <ming.lei@redhat.com>
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>,
Christoph Hellwig <hch@lst.de>,
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 V12 04/20] block: don't use bio->bi_vcnt to figure out segment number
Date: Mon, 26 Nov 2018 14:14:47 -0800 [thread overview]
Message-ID: <20181126221447.GE30411@vader> (raw)
In-Reply-To: <20181126021720.19471-5-ming.lei@redhat.com>
On Mon, Nov 26, 2018 at 10:17:04AM +0800, Ming Lei wrote:
> It is wrong to use bio->bi_vcnt to figure out how many segments
> there are in the bio even though CLONED flag isn't set on this bio,
> because this bio may be splitted or advanced.
>
> So always use bio_segments() in blk_recount_segments(), and it shouldn't
> cause any performance loss now because the physical segment number is figured
> out in blk_queue_split() and BIO_SEG_VALID is set meantime since
> bdced438acd83ad83a6c ("block: setup bi_phys_segments after splitting").
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
> Fixes: 76d8137a3113 ("blk-merge: recaculate segment if it isn't less than max segments")
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> block/blk-merge.c | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index e69d8f8ba819..51ec6ca56a0a 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -367,13 +367,7 @@ void blk_recalc_rq_segments(struct request *rq)
>
> void blk_recount_segments(struct request_queue *q, struct bio *bio)
> {
> - unsigned short seg_cnt;
> -
> - /* estimate segment number by bi_vcnt for non-cloned bio */
> - if (bio_flagged(bio, BIO_CLONED))
> - seg_cnt = bio_segments(bio);
> - else
> - seg_cnt = bio->bi_vcnt;
> + unsigned short seg_cnt = bio_segments(bio);
>
> if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
> (seg_cnt < queue_max_segments(q)))
> --
> 2.9.5
>
next prev parent reply other threads:[~2018-11-26 22:14 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-26 2:17 [PATCH V12 00/20] block: support multi-page bvec Ming Lei
2018-11-26 2:17 ` [PATCH V12 01/20] btrfs: remove various bio_offset arguments Ming Lei
2018-11-26 22:28 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 02/20] btrfs: look at bi_size for repair decisions Ming Lei
2018-11-26 22:46 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 03/20] block: remove the "cluster" flag Ming Lei
2018-11-26 22:12 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 04/20] block: don't use bio->bi_vcnt to figure out segment number Ming Lei
2018-11-26 22:14 ` Omar Sandoval [this message]
2018-11-26 2:17 ` [PATCH V12 05/20] block: remove bvec_iter_rewind() Ming Lei
2018-11-26 12:53 ` Christoph Hellwig
2018-11-26 22:16 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 06/20] block: rename bvec helpers Ming Lei
2018-11-26 8:17 ` Miguel Ojeda
2018-11-26 12:54 ` Christoph Hellwig
2018-11-26 22:18 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 07/20] block: introduce multi-page " Ming Lei
2018-11-26 12:55 ` Christoph Hellwig
2018-11-26 2:17 ` [PATCH V12 08/20] block: introduce bio_for_each_bvec() and rq_for_each_bvec() Ming Lei
2018-11-26 12:55 ` Christoph Hellwig
2018-11-26 2:17 ` [PATCH V12 09/20] block: use bio_for_each_bvec() to compute multi-page bvec count Ming Lei
2018-11-26 13:11 ` Christoph Hellwig
2018-11-26 22:37 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 10/20] block: use bio_for_each_bvec() to map sg Ming Lei
2018-11-26 13:11 ` Christoph Hellwig
2018-11-26 2:17 ` [PATCH V12 11/20] block: introduce bvec_last_segment() Ming Lei
2018-11-26 2:17 ` [PATCH V12 12/20] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2018-11-26 2:17 ` [PATCH V12 13/20] block: loop: pass multi-page bvec to iov_iter Ming Lei
2018-11-26 22:39 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 14/20] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2018-11-26 22:40 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 15/20] block: allow bio_for_each_segment_all() to iterate over multi-page bvec Ming Lei
2018-11-26 22:42 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 16/20] block: enable multipage bvecs Ming Lei
2018-11-26 12:58 ` Christoph Hellwig
2018-11-27 2:25 ` Ming Lei
2018-11-26 22:56 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 17/20] block: always define BIO_MAX_PAGES as 256 Ming Lei
2018-11-26 22:44 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 18/20] block: document usage of bio iterator helpers Ming Lei
2018-11-26 12:59 ` Christoph Hellwig
2018-11-26 22:43 ` Omar Sandoval
2018-11-26 2:17 ` [PATCH V12 19/20] block: kill QUEUE_FLAG_NO_SG_MERGE Ming Lei
2018-11-26 2:17 ` [PATCH V12 20/20] block: kill BLK_MQ_F_SG_MERGE Ming Lei
2018-11-28 13:44 ` [PATCH V12 00/20] block: support multi-page bvec Jens Axboe
2018-11-29 1:30 ` Ming Lei
2018-11-29 2:20 ` Jens Axboe
2018-11-29 3:30 ` Ming Lei
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