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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: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Webb Scales <webbnh@hp.com> Acked-by: Jens Axboe <axboe@kernel.dk> Tested-by: Bart Van Assche <bvanassche@acm.org> Tested-by: Robert Elliott <elliott@hp.com>
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cd9070c9c5
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2ccbb00808
1 changed files with 18 additions and 10 deletions
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@ -295,7 +295,8 @@ void scsi_device_unbusy(struct scsi_device *sdev)
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unsigned long flags;
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atomic_dec(&shost->host_busy);
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atomic_dec(&starget->target_busy);
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if (starget->can_queue > 0)
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atomic_dec(&starget->target_busy);
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if (unlikely(scsi_host_in_recovery(shost) &&
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(shost->host_failed || shost->host_eh_scheduled))) {
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@ -364,11 +365,12 @@ static inline bool scsi_device_is_busy(struct scsi_device *sdev)
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static inline bool scsi_target_is_busy(struct scsi_target *starget)
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{
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if (starget->can_queue > 0 &&
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atomic_read(&starget->target_busy) >= starget->can_queue)
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return true;
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if (atomic_read(&starget->target_blocked) > 0)
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return true;
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if (starget->can_queue > 0) {
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if (atomic_read(&starget->target_busy) >= starget->can_queue)
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return true;
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if (atomic_read(&starget->target_blocked) > 0)
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return true;
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}
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return false;
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}
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@ -1309,6 +1311,9 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
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spin_unlock_irq(shost->host_lock);
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}
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if (starget->can_queue <= 0)
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return 1;
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busy = atomic_inc_return(&starget->target_busy) - 1;
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if (atomic_read(&starget->target_blocked) > 0) {
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if (busy)
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@ -1324,7 +1329,7 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
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"unblocking target at zero depth\n"));
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}
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if (starget->can_queue > 0 && busy >= starget->can_queue)
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if (busy >= starget->can_queue)
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goto starved;
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return 1;
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@ -1334,7 +1339,8 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
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list_move_tail(&sdev->starved_entry, &shost->starved_list);
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spin_unlock_irq(shost->host_lock);
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out_dec:
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atomic_dec(&starget->target_busy);
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if (starget->can_queue > 0)
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atomic_dec(&starget->target_busy);
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return 0;
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}
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@ -1455,7 +1461,8 @@ static void scsi_kill_request(struct request *req, struct request_queue *q)
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*/
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atomic_inc(&sdev->device_busy);
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atomic_inc(&shost->host_busy);
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atomic_inc(&starget->target_busy);
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if (starget->can_queue > 0)
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atomic_inc(&starget->target_busy);
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blk_complete_request(req);
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}
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@ -1624,7 +1631,8 @@ static void scsi_request_fn(struct request_queue *q)
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return;
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host_not_ready:
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atomic_dec(&scsi_target(sdev)->target_busy);
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if (scsi_target(sdev)->can_queue > 0)
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atomic_dec(&scsi_target(sdev)->target_busy);
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not_ready:
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/*
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* lock q, handle tag, requeue req, and decrement device_busy. We
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