dm raid1: fix error count

Always increase the error count when I/O on a leg of a mirror fails.

The error count is used to decide whether to select an alternative
mirror leg. If the target doesn't use the "handle_errors" feature, the
error count is not updated and the bio can get requeued forever by the
read callback.

Fix it by increasing error_count before the handle_errors feature
checking.

Cc: [e-mail]
Signed-off-by: Milan Broz <[e-mail]>
Signed-off-by: Jonathan Brassow <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm-raid1.c

···
 	struct mirror_set *ms = m->ms;
 	struct mirror *new;
 
-	if (!errors_handled(ms))
-		return;
-
 	/*
 	 * error_count is used for nothing more than a
 	 * simple way to tell if a device has encountered
···
 	atomic_inc(&m->error_count);
 
 	if (test_and_set_bit(error_type, &m->error_type))
+		return;
+
+	if (!errors_handled(ms))
 		return;
 
 	if (m != get_default_mirror(ms))