md: Don't use remove_and_add_spares to remove failed devices from a read-only array

remove_and_add_spares is called in two places where the needs really
are very different.
remove_and_add_spares should not be called on an array which is about
to be reshaped as some extra devices might have been manually added
and that would remove them.  However if the array is 'read-auto',
that will currently happen, which is bad.

So in the 'ro != 0' case don't call remove_and_add_spares but simply
remove the failed devices as the comment suggests is needed.
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -7027,7 +7027,7 @@ static int remove_and_add_spares(mddev_t *mddev)
 			}
 		}
 
-	if (mddev->degraded && ! mddev->ro && !mddev->recovery_disabled) {
+	if (mddev->degraded && !mddev->recovery_disabled) {
 		list_for_each_entry(rdev, &mddev->disks, same_set) {
 			if (rdev->raid_disk >= 0 &&
 			    !test_bit(In_sync, &rdev->flags) &&
@@ -7150,7 +7150,20 @@ void md_check_recovery(mddev_t *mddev)
 			/* Only thing we do on a ro array is remove
 			 * failed devices.
 			 */
-			remove_and_add_spares(mddev);
+			mdk_rdev_t *rdev;
+			list_for_each_entry(rdev, &mddev->disks, same_set)
+				if (rdev->raid_disk >= 0 &&
+				    !test_bit(Blocked, &rdev->flags) &&
+				    test_bit(Faulty, &rdev->flags) &&
+				    atomic_read(&rdev->nr_pending)==0) {
+					if (mddev->pers->hot_remove_disk(
+						    mddev, rdev->raid_disk)==0) {
+						char nm[20];
+						sprintf(nm,"rd%d", rdev->raid_disk);
+						sysfs_remove_link(&mddev->kobj, nm);
+						rdev->raid_disk = -1;
+					}
+				}
 			clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 			goto unlock;
 		}