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 --- drivers/scsi/scsi.c | 21 ++++++------ drivers/scsi/scsi_lib.c | 82 +++++++++++++++++++++----------------------- drivers/scsi/scsi_sysfs.c | 10 +++++- include/scsi/scsi_device.h | 7 ++-- include/scsi/scsi_host.h | 7 ++-- 5 files changed, 64 insertions(+), 63 deletions(-) diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index a0b5e6f..0e8a077 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -752,17 +752,16 @@ void scsi_finish_command(struct scsi_cmnd *cmd) scsi_device_unbusy(sdev); - /* - * Clear the flags which say that the device/host is no longer - * capable of accepting new commands. These are set in scsi_queue.c - * for both the queue full condition on a device, and for a - * host full condition on the host. - * - * XXX(hch): What about locking? - */ - shost->host_blocked = 0; - starget->target_blocked = 0; - sdev->device_blocked = 0; + /* + * Clear the flags which say that the device/target/host is no longer + * capable of accepting new commands. + */ + if (atomic_read(&shost->host_blocked)) + atomic_set(&shost->host_blocked, 0); + if (atomic_read(&starget->target_blocked)) + atomic_set(&starget->target_blocked, 0); + if (atomic_read(&sdev->device_blocked)) + atomic_set(&sdev->device_blocked, 0); /* * If we have valid sense information, then some kind of recovery diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 6281595..a23e8c3 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -113,14 +113,16 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy) */ 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; } @@ -340,30 +342,39 @@ 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) - return 1; - if (sdev->device_blocked) - return 1; + return true; + if (atomic_read(&sdev->device_blocked) > 0) + return true; return 0; } -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) { + if (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; + if (shost->can_queue > 0) { + if (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 0; + return false; } static void scsi_starved_list_run(struct Scsi_Host *shost) @@ -1256,11 +1267,8 @@ static inline int scsi_dev_queue_ready(struct request_queue *q, unsigned int busy; busy = atomic_inc_return(&sdev->device_busy) - 1; - if (busy == 0 && sdev->device_blocked) { - /* - * unblock after device_blocked iterates to zero - */ - if (--sdev->device_blocked != 0) { + if (busy == 0 && atomic_read(&sdev->device_blocked) > 0) { + if (atomic_dec_return(&sdev->device_blocked) > 0) { blk_delay_queue(q, SCSI_QUEUE_DELAY); goto out_dec; } @@ -1270,7 +1278,7 @@ static inline int scsi_dev_queue_ready(struct request_queue *q, if (busy >= sdev->queue_depth) goto out_dec; - if (sdev->device_blocked) + if (atomic_read(&sdev->device_blocked) > 0) goto out_dec; return 1; @@ -1301,16 +1309,9 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, } busy = atomic_inc_return(&starget->target_busy) - 1; - if (busy == 0 && starget->target_blocked) { - /* - * 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 (busy == 0 && atomic_read(&starget->target_blocked) > 0) { + 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")); @@ -1318,7 +1319,7 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, if (starget->can_queue > 0 && busy >= starget->can_queue) goto starved; - if (starget->target_blocked) + if (atomic_read(&starget->target_blocked) > 0) goto starved; return 1; @@ -1347,16 +1348,9 @@ static inline int scsi_host_queue_ready(struct request_queue *q, return 0; busy = atomic_inc_return(&shost->host_busy) - 1; - if (busy == 0 && shost->host_blocked) { - /* - * 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 (busy == 0 && atomic_read(&shost->host_blocked) > 0) { + if (atomic_dec_return(&shost->host_blocked) > 0) goto out_dec; - } - spin_unlock_irq(shost->host_lock); SCSI_LOG_MLQUEUE(3, printk("scsi%d unblocking host at zero depth\n", @@ -1365,7 +1359,9 @@ static inline int scsi_host_queue_ready(struct request_queue *q, if (shost->can_queue > 0 && busy >= shost->can_queue) goto starved; - if (shost->host_blocked || shost->host_self_blocked) + if (atomic_read(&shost->host_blocked) > 0) + goto starved; + if (shost->host_self_blocked) goto starved; /* We're OK to process the command, so we can't be starved */ diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index c59e146..707a10c 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -585,7 +585,6 @@ static int scsi_sdev_check_buf_bit(const char *buf) /* * Create the actual show/store functions and data structures. */ -sdev_rd_attr (device_blocked, "%d\n"); sdev_rd_attr (queue_depth, "%d\n"); sdev_rd_attr (type, "%d\n"); sdev_rd_attr (scsi_level, "%d\n"); @@ -602,6 +601,15 @@ sdev_show_device_busy(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR(device_busy, S_IRUGO, sdev_show_device_busy, NULL); +static ssize_t +sdev_show_device_blocked(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct scsi_device *sdev = to_scsi_device(dev); + return snprintf(buf, 20, "%d\n", atomic_read(&sdev->device_blocked)); +} +static DEVICE_ATTR(device_blocked, S_IRUGO, sdev_show_device_blocked, NULL); + /* * TODO: can we make these symlinks to the block layer ones? */ diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index 7bb39e4..d72c842 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -82,6 +82,8 @@ struct scsi_device { struct list_head same_target_siblings; /* just the devices sharing same target id */ atomic_t device_busy; /* commands actually active on LLDD */ + atomic_t device_blocked; /* Device returned QUEUE_FULL. */ + spinlock_t list_lock; struct list_head cmd_list; /* queue of in use SCSI Command structures */ struct list_head starved_entry; @@ -173,8 +175,6 @@ struct scsi_device { struct list_head event_list; /* asserted events */ struct work_struct event_work; - unsigned int device_blocked; /* Device returned QUEUE_FULL. */ - unsigned int max_device_blocked; /* what device_blocked counts down from */ #define SCSI_DEFAULT_DEVICE_BLOCKED 3 @@ -272,12 +272,13 @@ struct scsi_target { * the same target will also. */ /* commands actually active on LLD. */ atomic_t target_busy; + atomic_t target_blocked; + /* * LLDs should set this in the slave_alloc host template callout. * If set to zero then there is not limit. */ unsigned int can_queue; - unsigned int target_blocked; unsigned int max_target_blocked; #define SCSI_DEFAULT_TARGET_BLOCKED 3 diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index 590e1af..c4e4875 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -604,6 +604,8 @@ struct Scsi_Host { struct blk_queue_tag *bqt; atomic_t host_busy; /* commands actually active on low-level */ + atomic_t host_blocked; + unsigned int host_failed; /* commands that failed. protected by host_lock */ unsigned int host_eh_scheduled; /* EH scheduled without command */ @@ -703,11 +705,6 @@ struct Scsi_Host { struct workqueue_struct *tmf_work_q; /* - * Host has rejected a command because it was busy. - */ - unsigned int host_blocked; - - /* * Value host_blocked counts down from */ unsigned int max_host_blocked; -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/