ide: improve handling of Power Management requests

Index: b/drivers/ide/ide-io.c
===================================================================
@@ -466,10 +466,14 @@ void do_ide_request(struct request_queue
 
 	if (!ide_lock_port(hwif)) {
 		ide_hwif_t *prev_port;
-
-		WARN_ON_ONCE(hwif->rq);
 repeat:
 		prev_port = hwif->host->cur_port;
+
+		if (drive->dev_flags & IDE_DFLAG_BLOCKED)
+			rq = hwif->rq;
+		else
+			WARN_ON_ONCE(hwif->rq);
+
 		if (drive->dev_flags & IDE_DFLAG_SLEEPING &&
 		    time_after(drive->sleep, jiffies)) {
 			ide_unlock_port(hwif);

@@ -496,43 +500,29 @@ repeat:
 		hwif->cur_dev = drive;
 		drive->dev_flags &= ~(IDE_DFLAG_SLEEPING | IDE_DFLAG_PARKED);
 
-		spin_unlock_irq(&hwif->lock);
-		spin_lock_irq(q->queue_lock);
-		/*
-		 * we know that the queue isn't empty, but this can happen
-		 * if the q->prep_rq_fn() decides to kill a request
-		 */
-		if (!rq)
+		if (rq == NULL) {
+			spin_unlock_irq(&hwif->lock);
+			spin_lock_irq(q->queue_lock);
+			/*
+			 * we know that the queue isn't empty, but this can
+			 * happen if ->prep_rq_fn() decides to kill a request
+			 */
 			rq = blk_fetch_request(drive->queue);
+			spin_unlock_irq(q->queue_lock);
+			spin_lock_irq(&hwif->lock);
 
-		spin_unlock_irq(q->queue_lock);
-		spin_lock_irq(&hwif->lock);
-
-		if (!rq) {
-			ide_unlock_port(hwif);
-			goto out;
+			if (rq == NULL) {
+				ide_unlock_port(hwif);
+				goto out;
+			}
 		}
 
 		/*
 		 * Sanity: don't accept a request that isn't a PM request
-		 * if we are currently power managed. This is very important as
-		 * blk_stop_queue() doesn't prevent the blk_fetch_request()
-		 * above to return us whatever is in the queue. Since we call
-		 * ide_do_request() ourselves, we end up taking requests while
-		 * the queue is blocked...
-		 * 
-		 * We let requests forced at head of queue with ide-preempt
-		 * though. I hope that doesn't happen too much, hopefully not
-		 * unless the subdriver triggers such a thing in its own PM
-		 * state machine.
+		 * if we are currently power managed.
 		 */
-		if ((drive->dev_flags & IDE_DFLAG_BLOCKED) &&
-		    blk_pm_request(rq) == 0 &&
-		    (rq->cmd_flags & REQ_PREEMPT) == 0) {
-			/* there should be no pending command at this point */
-			ide_unlock_port(hwif);
-			goto plug_device;
-		}
+		BUG_ON((drive->dev_flags & IDE_DFLAG_BLOCKED) &&
+		       blk_pm_request(rq) == 0);
 
 		hwif->rq = rq;