dm raid: fix discard support regression

Commit ecbfb9f118 ("dm raid: add raid level takeover support") moved the
configure_discard_support() call from raid_ctr() to raid_preresume().

Enabling/disabling discard _must_ happen during table load (through the
.ctr hook).  Fix this regression by moving the
configure_discard_support() call back to raid_ctr().

Fixes: ecbfb9f118 ("dm raid: add raid level takeover support")
Cc: stable@vger.kernel.org # 4.8+
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-raid.c

@@ -2999,6 +2999,9 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		}
 	}
 
+	/* Disable/enable discard support on raid set. */
+	configure_discard_support(rs);
+
 	mddev_unlock(&rs->md);
 	return 0;
 
@@ -3585,12 +3588,6 @@ static int raid_preresume(struct dm_target *ti)
 	if (test_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags))
 		rs_update_sbs(rs);
 
-	/*
-	 * Disable/enable discard support on raid set after any
-	 * conversion, because devices can have been added
-	 */
-	configure_discard_support(rs);
-
 	/* Load the bitmap from disk unless raid0 */
 	r = __load_dirty_region_bitmap(rs);
 	if (r)