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From:   linan666@huaweicloud.com
To:     song@kernel.org
Cc:     linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
        linan122@huawei.com, yukuai3@huawei.com, yi.zhang@huawei.com,
        houtao1@huawei.com, yangerkun@huawei.com
Subject: [PATCH v2] md/raid1: prioritize adding disk to 'removed' mirror
Date:   Tue, 27 Jun 2023 09:43:32 +0800
Message-Id: <20230627014332.3810102-1-linan666@huaweicloud.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Li Nan <linan122@huawei.com>

New disk should be added to "removed" position first instead of to be a
replacement. Commit 6090368abcb4 ("md/raid10: prioritize adding disk to
'removed' mirror") has fixed this issue for raid10. Fix it for raid1 now.

Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
---
Changes in v2:
 - improve commit log.

 drivers/md/raid1.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 68a9e2d9985b..320bede4bfab 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1782,7 +1782,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
 {
 	struct r1conf *conf = mddev->private;
 	int err = -EEXIST;
-	int mirror = 0;
+	int mirror = 0, repl_slot = -1;
 	struct raid1_info *p;
 	int first = 0;
 	int last = conf->raid_disks - 1;
@@ -1825,17 +1825,21 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
 			break;
 		}
 		if (test_bit(WantReplacement, &p->rdev->flags) &&
-		    p[conf->raid_disks].rdev == NULL) {
-			/* Add this device as a replacement */
-			clear_bit(In_sync, &rdev->flags);
-			set_bit(Replacement, &rdev->flags);
-			rdev->raid_disk = mirror;
-			err = 0;
-			conf->fullsync = 1;
-			rcu_assign_pointer(p[conf->raid_disks].rdev, rdev);
-			break;
-		}
+		    p[conf->raid_disks].rdev == NULL && repl_slot < 0)
+			repl_slot = mirror;
 	}
+
+	if (err && repl_slot >= 0) {
+		/* Add this device as a replacement */
+		p = conf->mirrors + repl_slot;
+		clear_bit(In_sync, &rdev->flags);
+		set_bit(Replacement, &rdev->flags);
+		rdev->raid_disk = repl_slot;
+		err = 0;
+		conf->fullsync = 1;
+		rcu_assign_pointer(p[conf->raid_disks].rdev, rdev);
+	}
+
 	print_conf(conf);
 	return err;
 }
-- 
2.39.2