linux-block.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>
Cc: linux-block@vger.kernel.org, Ming Lei <ming.lei@redhat.com>,
	Wang Shanker <shankerwangmiao@gmail.com>
Subject: [PATCH 1/2] block: fix discard request merge
Date: Wed,  9 Jun 2021 08:45:55 +0800	[thread overview]
Message-ID: <20210609004556.46928-2-ming.lei@redhat.com> (raw)
In-Reply-To: <20210609004556.46928-1-ming.lei@redhat.com>

ll_new_hw_segment() is reached only in case of single range discard
merge, and we don't have max discard segment size limit actually, so
it is wrong to run the following check:

if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))

it may be always false since req->nr_phys_segments is initialized as
one, and bio's segment count is still 1, blk_rq_get_max_segments(reg)
is 1 too.

Fix the issue by not doing the check and bypassing the calculation of
discard request's nr_phys_segments.

Based on analysis from Wang Shanker.

Reported-by: Wang Shanker <shankerwangmiao@gmail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-merge.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 4d97fb6dd226..bcdff1879c34 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -559,10 +559,14 @@ static inline unsigned int blk_rq_get_max_segments(struct request *rq)
 static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
 		unsigned int nr_phys_segs)
 {
-	if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
+	if (blk_integrity_merge_bio(req->q, req, bio) == false)
 		goto no_merge;
 
-	if (blk_integrity_merge_bio(req->q, req, bio) == false)
+	/* discard request merge won't add new segment */
+	if (req_op(req) == REQ_OP_DISCARD)
+		return 1;
+
+	if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
 		goto no_merge;
 
 	/*
-- 
2.31.1


  reply	other threads:[~2021-06-09  0:46 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-09  0:45 [PATCH 0/2] block: discard merge fix & improvement Ming Lei
2021-06-09  0:45 ` Ming Lei [this message]
2021-06-22  6:53   ` [PATCH 1/2] block: fix discard request merge Christoph Hellwig
2021-06-22  7:51     ` Ming Lei
2021-06-09  0:45 ` [PATCH 2/2] block: support bio merge for multi-range discard Ming Lei
2021-06-09  3:05   ` Wang Shanker
2021-06-09  6:12     ` Ming Lei
2021-06-09  6:57       ` Wang Shanker
2021-06-22  6:55   ` Christoph Hellwig
2021-06-22  8:35     ` Miao Wang
2021-06-14 22:00 ` [PATCH 0/2] block: discard merge fix & improvement Ming Lei
2021-06-22  3:53   ` Ming Lei

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=20210609004556.46928-2-ming.lei@redhat.com \
    --to=ming.lei@redhat.com \
    --cc=axboe@kernel.dk \
    --cc=hch@lst.de \
    --cc=linux-block@vger.kernel.org \
    --cc=shankerwangmiao@gmail.com \
    --subject='Re: [PATCH 1/2] block: fix discard request merge' \
    /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

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).