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

@@ -1437,18 +1437,19 @@ static void dm_wq_work(struct work_struct *work)
 
 	down_write(&md->io_lock);
 
-next_bio:
-	spin_lock_irq(&md->deferred_lock);
-	c = bio_list_pop(&md->deferred);
-	spin_unlock_irq(&md->deferred_lock);
+	while (1) {
+		spin_lock_irq(&md->deferred_lock);
+		c = bio_list_pop(&md->deferred);
+		spin_unlock_irq(&md->deferred_lock);
+
+		if (!c) {
+			clear_bit(DMF_BLOCK_IO, &md->flags);
+			break;
+		}
 
-	if (c) {
 		__split_and_process_bio(md, c);
-		goto next_bio;
 	}
 
-	clear_bit(DMF_BLOCK_IO, &md->flags);
-
 	up_write(&md->io_lock);
 }