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Commit a488e749 authored by Jens Axboe's avatar Jens Axboe
Browse files

scsi: convert to blk_delay_queue() 



It was always abuse to reuse the plugging infrastructure for this,
convert it to the (new) real API for delaying queueing a bit. A
default delay of 3 msec is defined, to match the previous
behaviour.

Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 0a41e90b

drivers/scsi/scsi_lib.c

+19 −25
Original line number Original line Diff line number Diff line
@@ -67,6 +67,13 @@ static struct scsi_host_sg_pool scsi_sg_pools[] = { 




struct kmem_cache *scsi_sdb_cache;

struct kmem_cache *scsi_sdb_cache;





/*

 * When to reinvoke queueing after a resource shortage. It's 3 msecs to

 * not change behaviour from the previous unplug mechanism, experimentation

 * may prove this needs changing.

 */

#define SCSI_QUEUE_DELAY	3



static void scsi_run_queue(struct request_queue *q);

static void scsi_run_queue(struct request_queue *q);





/*

/*
@@ -149,13 +156,6 @@ static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy) 
	/*

	/*

	 * Requeue this command.  It will go before all other commands

	 * Requeue this command.  It will go before all other commands

	 * that are already in the queue.

	 * that are already in the queue.

	 *

	 * NOTE: there is magic here about the way the queue is plugged if

	 * we have no outstanding commands.

	 * 

	 * Although we *don't* plug the queue, we call the request

	 * function.  The SCSI request function detects the blocked condition

	 * and plugs the queue appropriately.

	 */

	 */

	spin_lock_irqsave(q->queue_lock, flags);

	spin_lock_irqsave(q->queue_lock, flags);

	blk_requeue_request(q, cmd->request);

	blk_requeue_request(q, cmd->request);
@@ -1194,11 +1194,11 @@ int scsi_prep_return(struct request_queue *q, struct request *req, int ret) 
	case BLKPREP_DEFER:

	case BLKPREP_DEFER:

		/*

		/*

		 * If we defer, the blk_peek_request() returns NULL, but the

		 * If we defer, the blk_peek_request() returns NULL, but the

		 * queue must be restarted, so we plug here if no returning

		 * queue must be restarted, so we schedule a callback to happen

		 * command will automatically do that.

		 * shortly.

		 */

		 */

		if (sdev->device_busy == 0)

		if (sdev->device_busy == 0)

			blk_plug_device(q);

			blk_delay_queue(q, SCSI_QUEUE_DELAY);

		break;

		break;

	default:

	default:

		req->cmd_flags |= REQ_DONTPREP;

		req->cmd_flags |= REQ_DONTPREP;
@@ -1237,7 +1237,7 @@ static inline int scsi_dev_queue_ready(struct request_queue *q, 
				   sdev_printk(KERN_INFO, sdev,

				   sdev_printk(KERN_INFO, sdev,

				   "unblocking device at zero depth\n"));

				   "unblocking device at zero depth\n"));

		} else {

		} else {

			blk_plug_device(q);

			blk_delay_queue(q, SCSI_QUEUE_DELAY);

			return 0;

			return 0;

		}

		}

	}

	}
@@ -1467,7 +1467,7 @@ static void scsi_request_fn(struct request_queue *q) 
	 * the host is no longer able to accept any more requests.

	 * the host is no longer able to accept any more requests.

	 */

	 */

	shost = sdev->host;

	shost = sdev->host;

	while (!blk_queue_plugged(q)) {

	for (;;) {

		int rtn;

		int rtn;

		/*

		/*

		 * get next queueable request.  We do this early to make sure

		 * get next queueable request.  We do this early to make sure
@@ -1546,15 +1546,8 @@ static void scsi_request_fn(struct request_queue *q) 
		 */

		 */

		rtn = scsi_dispatch_cmd(cmd);

		rtn = scsi_dispatch_cmd(cmd);

		spin_lock_irq(q->queue_lock);

		spin_lock_irq(q->queue_lock);

		if(rtn) {

		if (rtn)

			/* we're refusing the command; because of

			goto out_delay;

			 * the way locks get dropped, we need to 

			 * check here if plugging is required */

			if(sdev->device_busy == 0)

				blk_plug_device(q);



			break;

		}

	}

	}





	goto out;

	goto out;
@@ -1573,8 +1566,9 @@ static void scsi_request_fn(struct request_queue *q) 
	spin_lock_irq(q->queue_lock);

	spin_lock_irq(q->queue_lock);

	blk_requeue_request(q, req);

	blk_requeue_request(q, req);

	sdev->device_busy--;

	sdev->device_busy--;

out_delay:

	if (sdev->device_busy == 0)

	if (sdev->device_busy == 0)

		blk_plug_device(q);

		blk_delay_queue(q, SCSI_QUEUE_DELAY);

out:

out:

	/* must be careful here...if we trigger the ->remove() function

	/* must be careful here...if we trigger the ->remove() function

	 * we cannot be holding the q lock */

	 * we cannot be holding the q lock */