linux-btrfs.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: 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, 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, Ming Lei <ming.lei@redhat.com>
Subject: [PATCH V13 02/19] block: don't use bio->bi_vcnt to figure out segment number
Date: Fri, 11 Jan 2019 19:01:10 +0800	[thread overview]
Message-ID: <20190111110127.21664-3-ming.lei@redhat.com> (raw)
In-Reply-To: <20190111110127.21664-1-ming.lei@redhat.com>

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: Omar Sandoval <osandov@fb.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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 71e9ac03f621..f85d878f313d 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


  parent reply	other threads:[~2019-01-11 11:02 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-11 11:01 [PATCH V13 00/19] block: support multi-page bvec Ming Lei
2019-01-11 11:01 ` [PATCH V13 01/19] btrfs: look at bi_size for repair decisions Ming Lei
2019-01-11 11:01 ` Ming Lei [this message]
2019-01-11 11:01 ` [PATCH V13 03/19] block: remove bvec_iter_rewind() Ming Lei
2019-01-11 11:01 ` [PATCH V13 04/19] block: rename bvec helpers Ming Lei
2019-01-11 11:01 ` [PATCH V13 05/19] block: introduce multi-page " Ming Lei
2019-01-11 11:01 ` [PATCH V13 06/19] block: introduce bio_for_each_bvec() and rq_for_each_bvec() Ming Lei
2019-01-11 11:01 ` [PATCH V13 07/19] block: use bio_for_each_bvec() to compute multi-page bvec count Ming Lei
2019-01-11 11:01 ` [PATCH V13 08/19] block: use bio_for_each_bvec() to map sg Ming Lei
2019-01-11 11:01 ` [PATCH V13 09/19] block: introduce bvec_last_segment() Ming Lei
2019-01-11 11:01 ` [PATCH V13 10/19] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2019-01-11 11:01 ` [PATCH V13 11/19] btrfs: use bvec_last_segment to get bio's last page Ming Lei
2019-01-11 11:01 ` [PATCH V13 12/19] block: loop: pass multi-page bvec to iov_iter Ming Lei
2019-01-11 11:01 ` [PATCH V13 13/19] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2019-01-11 11:01 ` [PATCH V13 14/19] block: allow bio_for_each_segment_all() to iterate over multi-page bvec Ming Lei
2019-01-11 11:01 ` [PATCH V13 15/19] block: enable multipage bvecs Ming Lei
2019-01-11 11:01 ` [PATCH V13 16/19] block: always define BIO_MAX_PAGES as 256 Ming Lei
2019-01-11 11:01 ` [PATCH V13 17/19] block: document usage of bio iterator helpers Ming Lei
2019-01-11 11:01 ` [PATCH V13 18/19] block: kill QUEUE_FLAG_NO_SG_MERGE Ming Lei
2019-01-11 11:01 ` [PATCH V13 19/19] block: kill BLK_MQ_F_SG_MERGE Ming Lei
2019-01-15  3:44 ` [PATCH V13 00/19] block: support multi-page bvec Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190111110127.21664-3-ming.lei@redhat.com \
    --to=ming.lei@redhat.com \
    --cc=axboe@kernel.dk \
    --cc=cluster-devel@redhat.com \
    --cc=colyli@suse.de \
    --cc=darrick.wong@oracle.com \
    --cc=dchinner@redhat.com \
    --cc=dm-devel@redhat.com \
    --cc=dsterba@suse.com \
    --cc=gaoxiang25@huawei.com \
    --cc=hch@lst.de \
    --cc=kent.overstreet@gmail.com \
    --cc=linux-bcache@vger.kernel.org \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-raid@vger.kernel.org \
    --cc=linux-xfs@vger.kernel.org \
    --cc=ooo@electrozaur.com \
    --cc=osandov@fb.com \
    --cc=rpeterso@redhat.com \
    --cc=sagi@grimberg.me \
    --cc=snitzer@redhat.com \
    --cc=tytso@mit.edu \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).