md/raid10: factor out dereference_rdev_and_rrdev()

[ Upstream commit b99f8fd2d91eb734f13098aa1cf337edaca454b7 ]

Factor out a helper to get 'rdev' and 'replacement' from config->mirrors.
Just to make code cleaner and prepare to fix the bug of io loss while
'replacement' replace 'rdev'.

There is no functional change.

Signed-off-by: Li Nan <linan122@huawei.com>
Link: https://lore.kernel.org/r/20230701080529.2684932-3-linan666@huaweicloud.com
Signed-off-by: Song Liu <song@kernel.org>
Stable-dep-of: 673643490b9a ("md/raid10: use dereference_rdev_and_rrdev() to get devices")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index d2098fcd6a270a60351a9d6a12fbc00eba464191..49bb79f48f362d826fe45ac4a71b89911dbd3eed 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1317,6 +1317,25 @@ static void raid10_write_one_disk(struct mddev *mddev, struct r10bio *r10_bio,
        }
 }
 
+static struct md_rdev *dereference_rdev_and_rrdev(struct raid10_info *mirror,
+                                                 struct md_rdev **prrdev)
+{
+       struct md_rdev *rdev, *rrdev;
+
+       rrdev = rcu_dereference(mirror->replacement);
+       /*
+        * Read replacement first to prevent reading both rdev and
+        * replacement as NULL during replacement replace rdev.
+        */
+       smp_mb();
+       rdev = rcu_dereference(mirror->rdev);
+       if (rdev == rrdev)
+               rrdev = NULL;
+
+       *prrdev = rrdev;
+       return rdev;
+}
+
 static void wait_blocked_dev(struct mddev *mddev, struct r10bio *r10_bio)
 {
        int i;
@@ -1460,15 +1479,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
                int d = r10_bio->devs[i].devnum;
                struct md_rdev *rdev, *rrdev;
 
-               rrdev = rcu_dereference(conf->mirrors[d].replacement);
-               /*
-                * Read replacement first to prevent reading both rdev and
-                * replacement as NULL during replacement replace rdev.
-                */
-               smp_mb();
-               rdev = rcu_dereference(conf->mirrors[d].rdev);
-               if (rdev == rrdev)
-                       rrdev = NULL;
+               rdev = dereference_rdev_and_rrdev(&conf->mirrors[d], &rrdev);
                if (rdev && (test_bit(Faulty, &rdev->flags)))
                        rdev = NULL;
                if (rrdev && (test_bit(Faulty, &rrdev->flags)))