ide: use per-device request queue locks (v2)

* Move hack for flush requests from choose_drive() to do_ide_request().

* Add ide_plug_device() helper and convert core IDE code from using
  per-hwgroup lock as a request lock to use the ->queue_lock instead.

* Remove no longer needed:
  - choose_drive() function
  - WAKEUP() macro
  - 'sleeping' flag from ide_hwif_t
  - 'service_{start,time}' fields from ide_drive_t

This patch results in much simpler and more maintainable code
(besides being a scalability improvement).

v2:
* Fixes/improvements based on review from Elias:
  - take as many requests off the queue as possible
  - remove now redundant BUG_ON()

Cc: Elias Oltmanns <eo@nebensachen.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-park.c

@@ -16,16 +16,19 @@ static void issue_park_cmd(ide_drive_t *drive, unsigned long timeout)
 	spin_lock_irq(&hwgroup->lock);
 	if (drive->dev_flags & IDE_DFLAG_PARKED) {
 		int reset_timer = time_before(timeout, drive->sleep);
+		int start_queue = 0;
 
 		drive->sleep = timeout;
 		wake_up_all(&ide_park_wq);
-		if (reset_timer && hwgroup->sleeping &&
-		    del_timer(&hwgroup->timer)) {
-			hwgroup->sleeping = 0;
-			ide_unlock_hwgroup(hwgroup);
+		if (reset_timer && del_timer(&hwgroup->timer))
+			start_queue = 1;
+		spin_unlock_irq(&hwgroup->lock);
+
+		if (start_queue) {
+			spin_lock_irq(q->queue_lock);
 			blk_start_queueing(q);
+			spin_unlock_irq(q->queue_lock);
 		}
-		spin_unlock_irq(&hwgroup->lock);
 		return;
 	}
 	spin_unlock_irq(&hwgroup->lock);

drivers/ide/ide-probe.c

@@ -881,8 +881,7 @@ static int ide_init_queue(ide_drive_t *drive)
 	 *	do not.
 	 */
 
-	q = blk_init_queue_node(do_ide_request, &hwif->hwgroup->lock,
-				hwif_to_node(hwif));
+	q = blk_init_queue_node(do_ide_request, NULL, hwif_to_node(hwif));
 	if (!q)
 		return 1;
 

include/linux/ide.h

@@ -603,8 +603,6 @@ struct ide_drive_s {
 	unsigned long dev_flags;
 
 	unsigned long sleep;		/* sleep until this time */
-	unsigned long service_start;	/* time we started last request */
-	unsigned long service_time;	/* service time of last request */
 	unsigned long timeout;		/* max time to wait for irq */
 
 	special_t	special;	/* special action flags */
@@ -872,8 +870,6 @@ typedef struct hwgroup_s {
 
 		/* BOOL: protects all fields below */
 	volatile int busy;
-		/* BOOL: wake us up on timer expiry */
-	unsigned int sleeping	: 1;
 		/* BOOL: polling active & poll_timeout field valid */
 	unsigned int polling	: 1;