dm: rearrange dm_wq_work

Refactor dm_wq_work() to make later patch more readable.
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm.c

@@ -1437,17 +1437,18 @@ static void dm_wq_work(struct work_struct *work)
 
 	down_write(&md->io_lock);
 
-next_bio:
+	while (1) {
 		spin_lock_irq(&md->deferred_lock);
 		c = bio_list_pop(&md->deferred);
 		spin_unlock_irq(&md->deferred_lock);
 
-	if (c) {
-		__split_and_process_bio(md, c);
-		goto next_bio;
+		if (!c) {
+			clear_bit(DMF_BLOCK_IO, &md->flags);
+			break;
 		}
 
-	clear_bit(DMF_BLOCK_IO, &md->flags);
+		__split_and_process_bio(md, c);
+	}
 
 	up_write(&md->io_lock);
 }