md: don't call spare_active in md_reap_sync_thread if all member devices can't work

[ Upstream commit 0d8ed0e9bf9643f27f4816dca61081784dedb38d ]

When add one disk to array, the md_reap_sync_thread is responsible
to activate the spare and set In_sync flag for the new member in
spare_active().

But if raid1 has one member disk A, and disk B is added to the array.
Then we offline A before all the datas are synchronized from A to B,
obviously B doesn't have the latest data as A, but B is still marked
with In_sync flag.

So let's not call spare_active under the condition, otherwise B is
still showed with 'U' state which is not correct.

Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/md/md.c

@@ -8948,7 +8948,8 @@ void md_reap_sync_thread(struct mddev *mddev)
 	/* resync has finished, collect result */
 	md_unregister_thread(&mddev->sync_thread);
 	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
-	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
+	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
+	    mddev->degraded != mddev->raid_disks) {
 		/* success...*/
 		/* activate any spares */
 		if (mddev->pers->spare_active(mddev)) {