md: don't clear MD_RECOVERY_FROZEN for new dm-raid until resume

After commit 9dbd1aa ("dm raid: add reshaping support to the
target") raid_ctr() will set MD_RECOVERY_FROZEN before md_run() and
expect to keep array frozen until resume. However, md_run() will clear
the flag by setting mddev->recovery to 0.

Before commit 1baae05 ("md: Don't ignore suspended array in
md_check_recovery()"), dm-raid actually relied on suspending to prevent
starting new sync_thread.

Fix this problem by keeping 'MD_RECOVERY_FROZEN' for dm-raid in
md_run().

Fixes: 1baae05 ("md: Don't ignore suspended array in md_check_recovery()")
Fixes: 9dbd1aa ("dm raid: add reshaping support to the target")
Cc: stable@vger.kernel.org # v6.7+
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Xiao Ni <xni@redhat.com>
Acked-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240305072306.2562024-2-yukuai1@huaweicloud.com

Author: YuKuai-huawei

drivers/md/md.c

@@ -6062,7 +6062,10 @@ int md_run(struct mddev *mddev)
 			pr_warn("True protection against single-disk failure might be compromised.\n");
 	}
 
-	mddev->recovery = 0;
+	/* dm-raid expect sync_thread to be frozen until resume */
+	if (mddev->gendisk)
+		mddev->recovery = 0;
+
 	/* may be over-ridden by personality */
 	mddev->resync_max_sectors = mddev->dev_sectors;