From: NeilBrown <neilb@suse.com>
Date: Thu, 2 Jun 2016 06:19:52 +0000 (+1000)
Subject: md/raid5: add rcu protection to rdev accesses in want_replace
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=3f232d6a95fc0fe539e0855ee7f3854b03c8104e;p=linux-beck.git

md/raid5: add rcu protection to rdev accesses in want_replace

Being in the middle of resync is no longer protection against failed
rdevs disappearing.  So add rcu protection.

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

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e56c7e0627fa..198b2a9eef98 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3239,15 +3239,16 @@ static int want_replace(struct stripe_head *sh, int disk_idx)
 {
 	struct md_rdev *rdev;
 	int rv = 0;
-	/* Doing recovery so rcu locking not required */
-	rdev = sh->raid_conf->disks[disk_idx].replacement;
+
+	rcu_read_lock();
+	rdev = rcu_dereference(sh->raid_conf->disks[disk_idx].replacement);
 	if (rdev
 	    && !test_bit(Faulty, &rdev->flags)
 	    && !test_bit(In_sync, &rdev->flags)
 	    && (rdev->recovery_offset <= sh->sector
 		|| rdev->mddev->recovery_cp <= sh->sector))
 		rv = 1;
-
+	rcu_read_unlock();
 	return rv;
 }