linux-kernel - [PATCH v2 3/3] md/raid10: use dereference_rdev_and

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Message-Id: <20230701080529.2684932-4-linan666@huaweicloud.com>
Date:   Sat,  1 Jul 2023 16:05:29 +0800
From:   linan666@...weicloud.com
To:     song@...nel.org, guoqing.jiang@...ud.ionos.com, xni@...hat.com,
        colyli@...e.de
Cc:     linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        linan122@...wei.com, yukuai3@...wei.com, yi.zhang@...wei.com,
        houtao1@...wei.com, yangerkun@...wei.com
Subject: [PATCH v2 3/3] md/raid10: use dereference_rdev_and_rrdev() to get devices

From: Li Nan <linan122@...wei.com>

Commit 2ae6aaf76912 ("md/raid10: fix io loss while replacement replace
rdev") reads replacement first to prevent io loss. However, there are same
issue in wait_blocked_dev() and raid10_handle_discard(), too. Fix it by
using dereference_rdev_and_rrdev() to get devices.

Fixes: d30588b2731f ("md/raid10: improve raid10 discard request")
Fixes: f2e7e269a752 ("md/raid10: pull the code that wait for blocked dev into one function")
Signed-off-by: Li Nan <linan122@...wei.com>
---
 drivers/md/raid10.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index a6c3806be903..cbaec6fce1d7 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1375,11 +1375,9 @@ static void wait_blocked_dev(struct mddev *mddev, struct r10bio *r10_bio)
 	blocked_rdev = NULL;
 	rcu_read_lock();
 	for (i = 0; i < conf->copies; i++) {
-		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
-		struct md_rdev *rrdev = rcu_dereference(
-			conf->mirrors[i].replacement);
-		if (rdev == rrdev)
-			rrdev = NULL;
+		struct md_rdev *rdev, *rrdev;
+
+		rdev = dereference_rdev_and_rrdev(&conf->mirrors[i], &rrdev);
 		if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
 			atomic_inc(&rdev->nr_pending);
 			blocked_rdev = rdev;
@@ -1815,15 +1813,12 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 	 */
 	rcu_read_lock();
 	for (disk = 0; disk < geo->raid_disks; disk++) {
-		struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev);
-		struct md_rdev *rrdev = rcu_dereference(
-			conf->mirrors[disk].replacement);
+		struct md_rdev *rdev, *rrdev;
 
+		rdev = dereference_rdev_and_rrdev(&conf->mirrors[disk], &rrdev);
 		r10_bio->devs[disk].bio = NULL;
 		r10_bio->devs[disk].repl_bio = NULL;
 
-		if (rdev == rrdev)
-			rrdev = NULL;
 		if (rdev && (test_bit(Faulty, &rdev->flags)))
 			rdev = NULL;
 		if (rrdev && (test_bit(Faulty, &rrdev->flags)))
-- 
2.39.2