md-cluster: protect md_find_rdev_nr_rcu with rcu lock

We need to use rcu_read_lock/unlock to avoid potential
race.

Reported-by: Shaohua Li <shli@fb.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 67a7358..b4dc211 100644 (file)
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -489,9 +489,10 @@ static void process_metadata_update(struct mddev *mddev, struct cluster_msg *msg
 
 static void process_remove_disk(struct mddev *mddev, struct cluster_msg *msg)
 {
-       struct md_rdev *rdev = md_find_rdev_nr_rcu(mddev,
-                                                  le32_to_cpu(msg->raid_slot));
+       struct md_rdev *rdev;
 
+       rcu_read_lock();
+       rdev = md_find_rdev_nr_rcu(mddev, le32_to_cpu(msg->raid_slot));
        if (rdev) {
                set_bit(ClusterRemove, &rdev->flags);
                set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
@@ -500,18 +501,21 @@ static void process_remove_disk(struct mddev *mddev, struct cluster_msg *msg)
        else
                pr_warn("%s: %d Could not find disk(%d) to REMOVE\n",
                        __func__, __LINE__, le32_to_cpu(msg->raid_slot));
+       rcu_read_unlock();
 }
 
 static void process_readd_disk(struct mddev *mddev, struct cluster_msg *msg)
 {
-       struct md_rdev *rdev = md_find_rdev_nr_rcu(mddev,
-                                                  le32_to_cpu(msg->raid_slot));
+       struct md_rdev *rdev;
 
+       rcu_read_lock();
+       rdev = md_find_rdev_nr_rcu(mddev, le32_to_cpu(msg->raid_slot));
        if (rdev && test_bit(Faulty, &rdev->flags))
                clear_bit(Faulty, &rdev->flags);
        else
                pr_warn("%s: %d Could not find disk(%d) which is faulty",
                        __func__, __LINE__, le32_to_cpu(msg->raid_slot));
+       rcu_read_unlock();
 }
 
 static int process_recvd_msg(struct mddev *mddev, struct cluster_msg *msg)