md/multipath: add rcu protection to rdev access in multipath_status.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index dd483bb2e111..69244de2036b 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -141,17 +141,19 @@ static void multipath_make_request(struct mddev *mddev, struct bio * bio)
         return;
 }
 
-static void multipath_status (struct seq_file *seq, struct mddev *mddev)
+static void multipath_status(struct seq_file *seq, struct mddev *mddev)
 {
         struct mpconf *conf = mddev->private;
         int i;
 
         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
                     conf->raid_disks - mddev->degraded);
-        for (i = 0; i < conf->raid_disks; i++)
-                seq_printf (seq, "%s",
-                               conf->multipaths[i].rdev &&
-                               test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
+        rcu_read_lock();
+        for (i = 0; i < conf->raid_disks; i++) {
+                struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
+                seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
+        }
+        rcu_read_unlock();
         seq_printf (seq, "]");
 }