From cd9070c9c512ff7995f9019392e0ae548df3a088 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 23 Jan 2014 12:07:41 +0100 Subject: scsi: fix the {host,target,device}_blocked counter mess Seems like these counters are missing any sort of synchronization for updates, as a over 10 year old comment from me noted. Fix this by using atomic counters, and while we're at it also make sure they are in the same cacheline as the _busy counters and not needlessly stored to in every I/O completion. With the new model the _busy counters can temporarily go negative, so all the readers are updated to check for > 0 values. Longer term every successful I/O completion will reset the counters to zero, so the temporarily negative values will not cause any harm. Signed-off-by: Christoph Hellwig Reviewed-by: Martin K. Petersen Reviewed-by: Webb Scales Acked-by: Jens Axboe Tested-by: Bart Van Assche Tested-by: Robert Elliott --- drivers/scsi/scsi_lib.c | 66 ++++++++++++++++++++++++------------------------- 1 file changed, 33 insertions(+), 33 deletions(-) (limited to 'drivers/scsi/scsi_lib.c') diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 1ddf0fb43b59..69da4cb5cb13 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -99,14 +99,16 @@ scsi_set_blocked(struct scsi_cmnd *cmd, int reason) */ switch (reason) { case SCSI_MLQUEUE_HOST_BUSY: - host->host_blocked = host->max_host_blocked; + atomic_set(&host->host_blocked, host->max_host_blocked); break; case SCSI_MLQUEUE_DEVICE_BUSY: case SCSI_MLQUEUE_EH_RETRY: - device->device_blocked = device->max_device_blocked; + atomic_set(&device->device_blocked, + device->max_device_blocked); break; case SCSI_MLQUEUE_TARGET_BUSY: - starget->target_blocked = starget->max_target_blocked; + atomic_set(&starget->target_blocked, + starget->max_target_blocked); break; } } @@ -351,29 +353,35 @@ static void scsi_single_lun_run(struct scsi_device *current_sdev) spin_unlock_irqrestore(shost->host_lock, flags); } -static inline int scsi_device_is_busy(struct scsi_device *sdev) +static inline bool scsi_device_is_busy(struct scsi_device *sdev) { - if (atomic_read(&sdev->device_busy) >= sdev->queue_depth || - sdev->device_blocked) - return 1; - return 0; + if (atomic_read(&sdev->device_busy) >= sdev->queue_depth) + return true; + if (atomic_read(&sdev->device_blocked) > 0) + return true; + return false; } -static inline int scsi_target_is_busy(struct scsi_target *starget) +static inline bool scsi_target_is_busy(struct scsi_target *starget) { - return ((starget->can_queue > 0 && - atomic_read(&starget->target_busy) >= starget->can_queue) || - starget->target_blocked); + if (starget->can_queue > 0 && + atomic_read(&starget->target_busy) >= starget->can_queue) + return true; + if (atomic_read(&starget->target_blocked) > 0) + return true; + return false; } -static inline int scsi_host_is_busy(struct Scsi_Host *shost) +static inline bool scsi_host_is_busy(struct Scsi_Host *shost) { - if ((shost->can_queue > 0 && - atomic_read(&shost->host_busy) >= shost->can_queue) || - shost->host_blocked || shost->host_self_blocked) - return 1; - - return 0; + if (shost->can_queue > 0 && + atomic_read(&shost->host_busy) >= shost->can_queue) + return true; + if (atomic_read(&shost->host_blocked) > 0) + return true; + if (shost->host_self_blocked) + return true; + return false; } static void scsi_starved_list_run(struct Scsi_Host *shost) @@ -1256,14 +1264,14 @@ static inline int scsi_dev_queue_ready(struct request_queue *q, unsigned int busy; busy = atomic_inc_return(&sdev->device_busy) - 1; - if (sdev->device_blocked) { + if (atomic_read(&sdev->device_blocked)) { if (busy) goto out_dec; /* * unblock after device_blocked iterates to zero */ - if (--sdev->device_blocked != 0) { + if (atomic_dec_return(&sdev->device_blocked) > 0) { blk_delay_queue(q, SCSI_QUEUE_DELAY); goto out_dec; } @@ -1302,19 +1310,15 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, } busy = atomic_inc_return(&starget->target_busy) - 1; - if (starget->target_blocked) { + if (atomic_read(&starget->target_blocked) > 0) { if (busy) goto starved; /* * unblock after target_blocked iterates to zero */ - spin_lock_irq(shost->host_lock); - if (--starget->target_blocked != 0) { - spin_unlock_irq(shost->host_lock); + if (atomic_dec_return(&starget->target_blocked) > 0) goto out_dec; - } - spin_unlock_irq(shost->host_lock); SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget, "unblocking target at zero depth\n")); @@ -1349,19 +1353,15 @@ static inline int scsi_host_queue_ready(struct request_queue *q, return 0; busy = atomic_inc_return(&shost->host_busy) - 1; - if (shost->host_blocked) { + if (atomic_read(&shost->host_blocked) > 0) { if (busy) goto starved; /* * unblock after host_blocked iterates to zero */ - spin_lock_irq(shost->host_lock); - if (--shost->host_blocked != 0) { - spin_unlock_irq(shost->host_lock); + if (atomic_dec_return(&shost->host_blocked) > 0) goto out_dec; - } - spin_unlock_irq(shost->host_lock); SCSI_LOG_MLQUEUE(3, shost_printk(KERN_INFO, shost, -- cgit v1.2.3