dm zoned: return NULL if dmz_get_zone_for_reclaim() fails to find a zone

The only case where dmz_get_zone_for_reclaim() cannot return a zone is
if the respective lists are empty. So we should just return a simple
NULL value here as we really don't have an error code which would make
sense.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-zoned-metadata.c

@@ -1845,7 +1845,7 @@ static struct dm_zone *dmz_get_rnd_zone_for_reclaim(struct dmz_metadata *zmd)
 			return dzone;
 	}
 
-	return ERR_PTR(-EBUSY);
+	return NULL;
 }
 
 /*
@@ -1865,7 +1865,7 @@ static struct dm_zone *dmz_get_seq_zone_for_reclaim(struct dmz_metadata *zmd)
 			return zone;
 	}
 
-	return ERR_PTR(-EBUSY);
+	return NULL;
 }
 
 /*

drivers/md/dm-zoned-reclaim.c

@@ -352,8 +352,8 @@ static int dmz_do_reclaim(struct dmz_reclaim *zrc)
 
 	/* Get a data zone */
 	dzone = dmz_get_zone_for_reclaim(zmd);
-	if (IS_ERR(dzone))
-		return PTR_ERR(dzone);
+	if (!dzone)
+		return -EBUSY;
 
 	start = jiffies;
 	if (dmz_is_rnd(dzone)) {