md/raid1: Avoid raid1 resync getting stuck

close_sync() needs to set conf->next_resync to a large, but safe value
below MaxSector and use it to determine whether or not to set
start_next_window in wait_barrier()

Solution suggested by Neil Brown.
Reported-by: Nate Dailey <nate.dailey@stratus.com>
Tested-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>

drivers/md/raid1.c

@@ -881,8 +881,7 @@ static sector_t wait_barrier(struct r1conf *conf, struct bio *bio)
 	}
 
 	if (bio && bio_data_dir(bio) == WRITE) {
-		if (bio->bi_iter.bi_sector >=
-		    conf->mddev->curr_resync_completed) {
+		if (bio->bi_iter.bi_sector >= conf->next_resync) {
 			if (conf->start_next_window == MaxSector)
 				conf->start_next_window =
 					conf->next_resync +
@@ -1516,7 +1515,7 @@ static void close_sync(struct r1conf *conf)
 	conf->r1buf_pool = NULL;
 
 	spin_lock_irq(&conf->resync_lock);
-	conf->next_resync = 0;
+	conf->next_resync = MaxSector - 2 * NEXT_NORMALIO_DISTANCE;
 	conf->start_next_window = MaxSector;
 	conf->current_window_requests +=
 		conf->next_window_requests;