md: ensure resync is prioritized over recovery

If a new disk is added during resync, the resync process is interrupted,
and recovery is triggered, causing the previous resync to be lost. In
reality, disk addition should not terminate resync, fix it.

Steps to reproduce the issue:
  mdadm -CR /dev/md0 -l1 -n3 -x1 /dev/sd[abcd]
  mdadm --fail /dev/md0 /dev/sdc

Fixes: 24dd469 ("[PATCH] md: allow a manual resync with md")
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/linux-raid/20250213131530.3698600-1-linan666@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Author: Li Nan

drivers/md/md.c

@@ -9460,6 +9460,13 @@ static bool md_choose_sync_action(struct mddev *mddev, int *spares)
 		return true;
 	}
 
+	/* Check if resync is in progress. */
+	if (mddev->recovery_cp < MaxSector) {
+		set_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+		clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
+		return true;
+	}
+
 	/*
 	 * Remove any failed drives, then add spares if possible. Spares are
 	 * also removed and re-added, to allow the personality to fail the
@@ -9476,13 +9483,6 @@ static bool md_choose_sync_action(struct mddev *mddev, int *spares)
 		return true;
 	}
 
-	/* Check if recovery is in progress. */
-	if (mddev->recovery_cp < MaxSector) {
-		set_bit(MD_RECOVERY_SYNC, &mddev->recovery);
-		clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
-		return true;
-	}
-
 	/* Delay to choose resync/check/repair in md_do_sync(). */
 	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
 		return true;