diff options
| author | Christoph Hellwig <hch@lst.de> | 2014-03-26 13:35:00 +0400 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2014-07-26 01:16:05 +0400 |
| commit | 2ccbb00808465338b57c39f38c0b1e7ce69e2bb1 (patch) | |
| tree | e7a6e51c60b86d546a114441cc4e4dc6c46252d1 /drivers/scsi/scsi_lib.c | |
| parent | cd9070c9c512ff7995f9019392e0ae548df3a088 (diff) | |
| download | linux-2ccbb00808465338b57c39f38c0b1e7ce69e2bb1.tar.xz | |
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>
Diffstat (limited to 'drivers/scsi/scsi_lib.c')
| -rw-r--r-- | drivers/scsi/scsi_lib.c | 28 |
1 files changed, 18 insertions, 10 deletions
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 69da4cb5cb13..a643353584b5 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -295,7 +295,8 @@ void scsi_device_unbusy(struct scsi_device *sdev) unsigned long flags; atomic_dec(&shost->host_busy); - atomic_dec(&starget->target_busy); + if (starget->can_queue > 0) + atomic_dec(&starget->target_busy); if (unlikely(scsi_host_in_recovery(shost) && (shost->host_failed || shost->host_eh_scheduled))) { @@ -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) - return true; - if (atomic_read(&starget->target_blocked) > 0) - return true; + 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; @@ -1334,7 +1339,8 @@ starved: list_move_tail(&sdev->starved_entry, &shost->starved_list); spin_unlock_irq(shost->host_lock); out_dec: - atomic_dec(&starget->target_busy); + if (starget->can_queue > 0) + atomic_dec(&starget->target_busy); return 0; } @@ -1455,7 +1461,8 @@ static void scsi_kill_request(struct request *req, struct request_queue *q) */ atomic_inc(&sdev->device_busy); atomic_inc(&shost->host_busy); - atomic_inc(&starget->target_busy); + if (starget->can_queue > 0) + atomic_inc(&starget->target_busy); blk_complete_request(req); } @@ -1624,7 +1631,8 @@ static void scsi_request_fn(struct request_queue *q) return; host_not_ready: - atomic_dec(&scsi_target(sdev)->target_busy); + if (scsi_target(sdev)->can_queue > 0) + atomic_dec(&scsi_target(sdev)->target_busy); not_ready: /* * lock q, handle tag, requeue req, and decrement device_busy. We |