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Commit 2ccbb008 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

scsi: only maintain target_blocked if the driver has a target queue limit 



This saves us an atomic operation for each I/O submission and completion
for the usual case where the driver doesn't set a per-target can_queue
value.  Only a few iscsi hardware offload drivers set the per-target
can_queue value at the moment.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: default avatarWebb Scales <webbnh@hp.com>
Acked-by: default avatarJens Axboe <axboe@kernel.dk>
Tested-by: default avatarBart Van Assche <bvanassche@acm.org>
Tested-by: default avatarRobert Elliott <elliott@hp.com>
parent cd9070c9

drivers/scsi/scsi_lib.c

+18 −10
Original line number Diff line number Diff line
@@ -295,6 +295,7 @@ void scsi_device_unbusy(struct scsi_device *sdev) 
	unsigned long flags;



	atomic_dec(&shost->host_busy);

	if (starget->can_queue > 0)

		atomic_dec(&starget->target_busy);



	if (unlikely(scsi_host_in_recovery(shost) &&
@@ -364,11 +365,12 @@ static inline bool scsi_device_is_busy(struct scsi_device *sdev) 


static inline bool scsi_target_is_busy(struct scsi_target *starget)

{

	if (starget->can_queue > 0 &&

	    atomic_read(&starget->target_busy) >= starget->can_queue)

	if (starget->can_queue > 0) {

		if (atomic_read(&starget->target_busy) >= starget->can_queue)

			return true;

		if (atomic_read(&starget->target_blocked) > 0)

			return true;

	}

	return false;

}
@@ -1309,6 +1311,9 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, 
		spin_unlock_irq(shost->host_lock);

	}



	if (starget->can_queue <= 0)

		return 1;



	busy = atomic_inc_return(&starget->target_busy) - 1;

	if (atomic_read(&starget->target_blocked) > 0) {

		if (busy)
@@ -1324,7 +1329,7 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, 
				 "unblocking target at zero depth\n"));

	}



	if (starget->can_queue > 0 && busy >= starget->can_queue)

	if (busy >= starget->can_queue)

		goto starved;



	return 1;
@@ -1334,6 +1339,7 @@ starved: 
	list_move_tail(&sdev->starved_entry, &shost->starved_list);

	spin_unlock_irq(shost->host_lock);

out_dec:

	if (starget->can_queue > 0)

		atomic_dec(&starget->target_busy);

	return 0;

}
@@ -1455,6 +1461,7 @@ static void scsi_kill_request(struct request *req, struct request_queue *q) 
	 */

	atomic_inc(&sdev->device_busy);

	atomic_inc(&shost->host_busy);

	if (starget->can_queue > 0)

		atomic_inc(&starget->target_busy);



	blk_complete_request(req);
@@ -1624,6 +1631,7 @@ static void scsi_request_fn(struct request_queue *q) 
	return;



 host_not_ready:

	if (scsi_target(sdev)->can_queue > 0)

		atomic_dec(&scsi_target(sdev)->target_busy);

 not_ready:

	/*