linux-kernel - [PATCH] md/raid1: fix data lost for writemostly rdev

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Message-Id: <20250903014140.3690499-1-yukuai1@huaweicloud.com>
Date: Wed,  3 Sep 2025 09:41:40 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: song@...nel.org,
	ian@...are.dropbear.id.au
Cc: linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH] md/raid1: fix data lost for writemostly rdev

From: Yu Kuai <yukuai3@...wei.com>

If writemostly is enabled, alloc_behind_master_bio() will allocate a new
bio for rdev, with bi_opf set to 0. Later, raid1_write_request() will
clone from this bio, hence bi_opf is still 0 for the cloned bio. Submit
this cloned bio will end up to be read, causing write data lost.

Fix this problem by inheriting bi_opf from original bio for
behind_mast_bio.

Fixes: e879a0d9cb08 ("md/raid1,raid10: don't ignore IO flags")
Reported-and-tested-by: Ian Dall <ian@...are.dropbear.id.au>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220507
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/md/raid1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index f8434049f9b1..f391fd56d67f 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1225,7 +1225,7 @@ static void alloc_behind_master_bio(struct r1bio *r1_bio,
 	int i = 0;
 	struct bio *behind_bio = NULL;
 
-	behind_bio = bio_alloc_bioset(NULL, vcnt, 0, GFP_NOIO,
+	behind_bio = bio_alloc_bioset(NULL, vcnt, bio->bi_opf, GFP_NOIO,
 				      &r1_bio->mddev->bio_set);
 
 	/* discard op, we don't support writezero/writesame yet */
-- 
2.39.2