fix queue run on returning I/O [axboe@suse.de]

On returning I/O, need to unplug the queue before we call the queue_fn. 
This fixes a problem in 2.5.48 where the aic7xxx driver hangs under e2fsck.

drivers/block/ll_rw_blk.c

@@ -1037,6 +1037,16 @@ void blk_stop_queue(request_queue_t *q)
 	spin_unlock_irqrestore(q->queue_lock, flags);
 }
 
+/**
+ * blk_run_queue - run a single device queue
+ * @q	The queue to run
+ */
+void __blk_run_queue(request_queue_t *q)
+{
+	blk_remove_plug(q);
+	q->request_fn(q);
+}
+
 /**
  * blk_run_queues - fire all plugged queues
  *
@@ -2198,4 +2208,5 @@ EXPORT_SYMBOL(blk_queue_invalidate_tags);
 EXPORT_SYMBOL(blk_start_queue);
 EXPORT_SYMBOL(blk_stop_queue);
 EXPORT_SYMBOL(__blk_stop_queue);
+EXPORT_SYMBOL(__blk_run_queue);
 EXPORT_SYMBOL(blk_run_queues);

drivers/scsi/scsi_error.c

@@ -1479,8 +1479,6 @@ static void scsi_restart_operations(struct Scsi_Host *shost)
 	 */
 	spin_lock_irqsave(shost->host_lock, flags);
 	for (sdev = shost->host_queue; sdev; sdev = sdev->next) {
-		request_queue_t *q = &sdev->request_queue;
-
 		if ((shost->can_queue > 0 &&
 		     (shost->host_busy >= shost->can_queue))
 		    || (shost->host_blocked)
@@ -1488,7 +1486,7 @@ static void scsi_restart_operations(struct Scsi_Host *shost)
 			break;
 		}
 
-		q->request_fn(q);
+		__blk_run_queue(&sdev->request_queue);
 	}
 	spin_unlock_irqrestore(shost->host_lock, flags);
 }

drivers/scsi/scsi_lib.c

@@ -227,7 +227,7 @@ void scsi_queue_next_request(request_queue_t * q, Scsi_Cmnd * SCpnt)
 	/*
 	 * Just hit the requeue function for the queue.
 	 */
-	q->request_fn(q);
+	__blk_run_queue(q);
 
 	SDpnt = (Scsi_Device *) q->queuedata;
 	SHpnt = SDpnt->host;
@@ -240,8 +240,6 @@ void scsi_queue_next_request(request_queue_t * q, Scsi_Cmnd * SCpnt)
 	 * use function pointers to pick the right one.
 	 */
 	if (SDpnt->single_lun && blk_queue_empty(q) && SDpnt->device_busy ==0) {
-		request_queue_t *q;
-
 		for (SDpnt = SHpnt->host_queue; SDpnt; SDpnt = SDpnt->next) {
 			if (((SHpnt->can_queue > 0)
 			     && (SHpnt->host_busy >= SHpnt->can_queue))
@@ -251,8 +249,7 @@ void scsi_queue_next_request(request_queue_t * q, Scsi_Cmnd * SCpnt)
 				break;
 			}
 
-			q = &SDpnt->request_queue;
-			q->request_fn(q);
+			__blk_run_queue(&SDpnt->request_queue);
 		}
 	}
 
@@ -267,7 +264,6 @@ void scsi_queue_next_request(request_queue_t * q, Scsi_Cmnd * SCpnt)
 	all_clear = 1;
 	if (SHpnt->some_device_starved) {
 		for (SDpnt = SHpnt->host_queue; SDpnt; SDpnt = SDpnt->next) {
-			request_queue_t *q;
 			if ((SHpnt->can_queue > 0 && (SHpnt->host_busy >= SHpnt->can_queue))
 			    || (SHpnt->host_blocked) 
 			    || (SHpnt->host_self_blocked)) {
@@ -276,8 +272,7 @@ void scsi_queue_next_request(request_queue_t * q, Scsi_Cmnd * SCpnt)
 			if (SDpnt->device_blocked || !SDpnt->starved) {
 				continue;
 			}
-			q = &SDpnt->request_queue;
-			q->request_fn(q);
+			__blk_run_queue(&SDpnt->request_queue);
 			all_clear = 0;
 		}
 		if (SDpnt == NULL && all_clear) {

include/linux/blkdev.h

@@ -321,6 +321,7 @@ extern int scsi_cmd_ioctl(struct block_device *, unsigned int, unsigned long);
 extern void blk_start_queue(request_queue_t *q);
 extern void blk_stop_queue(request_queue_t *q);
 extern void __blk_stop_queue(request_queue_t *q);
+extern void __blk_run_queue(request_queue_t *q);
 
 static inline request_queue_t *bdev_get_queue(struct block_device *bdev)
 {