From 0b020e85bdd5765aac2440848e7a927069f5f83c Mon Sep 17 00:00:00 2001
From: Song Liu <songliubraving@fb.com>
Date: Thu, 3 Sep 2015 23:00:35 -0700
Subject: skip match_mddev_units check for special roles

match_mddev_units is used to check whether 2 RAID arrays share
same disk(s). Arrays that share disk(s) will not do resync at the
same time for better performance (fewer HDD seek). However, this
check should not apply to Spare, Faulty, and Journal disks, as
they do not paticipate in resync.

In this patch, match_mddev_units skips check for disks with flag
"Faulty" or "Journal" or raid_disk < 0.

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

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 89149ac..fe67272 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1935,13 +1935,23 @@ static int match_mddev_units(struct mddev *mddev1, struct mddev *mddev2)
 	struct md_rdev *rdev, *rdev2;
 
 	rcu_read_lock();
-	rdev_for_each_rcu(rdev, mddev1)
-		rdev_for_each_rcu(rdev2, mddev2)
+	rdev_for_each_rcu(rdev, mddev1) {
+		if (test_bit(Faulty, &rdev->flags) ||
+		    test_bit(Journal, &rdev->flags) ||
+		    rdev->raid_disk == -1)
+			continue;
+		rdev_for_each_rcu(rdev2, mddev2) {
+			if (test_bit(Faulty, &rdev2->flags) ||
+			    test_bit(Journal, &rdev2->flags) ||
+			    rdev2->raid_disk == -1)
+				continue;
 			if (rdev->bdev->bd_contains ==
 			    rdev2->bdev->bd_contains) {
 				rcu_read_unlock();
 				return 1;
 			}
+		}
+	}
 	rcu_read_unlock();
 	return 0;
 }
-- 
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