Re: [PATCH -next] md/raid1: don't split discard io for write behind
From: Song Liu <song@kernel.org>
Date: 2023-10-09 23:33:40
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On Fri, Oct 6, 2023 at 8:24 PM Yu Kuai [off-list ref] wrote:
From: Yu Kuai <redacted> Currently, discad io is treated the same as normal write io, and for write behind case, io size is limited to: BIO_MAX_VECS * (PAGE_SIZE >> 9) For 0.5KB sector size and 4KB PAGE_SIZE, this is just 1MB. For consequence, if 'WriteMostly' is set to one of the underlying disks, then diskcard io will be splited into 1MB and it will take a long time for the diskcard to finish. Fix this problem by disable write behind for discard io. Reported-by: Roman Mamedov <redacted> Closes: https://lore.kernel.org/all/6a1165f7-c792-c054-b8f0-1ad4f7b8ae01@ultracoder.org/ (local) Reported-and-tested-by: Kirill Kirilenko <redacted> Signed-off-by: Yu Kuai <redacted>
Applied to md-next. Thanks! Song
quoted hunk ↗ jump to hunk
--- drivers/md/raid1.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 3a78f79ee6d5..35d12948e0a9 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c@@ -1345,6 +1345,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, int first_clone; int max_sectors; bool write_behind = false; + bool is_discard = (bio_op(bio) == REQ_OP_DISCARD); if (mddev_is_clustered(mddev) && md_cluster_ops->area_resyncing(mddev, WRITE,@@ -1405,7 +1406,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, * write-mostly, which means we could allocate write behind * bio later. */ - if (rdev && test_bit(WriteMostly, &rdev->flags)) + if (!is_discard && rdev && test_bit(WriteMostly, &rdev->flags)) write_behind = true; if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) { --2.39.2