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scsi: convert host_busy to atomic_t 

Avoid taking the host-wide host_lock to check the per-host queue limit.
Instead we do an atomic_inc_return early on to grab our slot in the queue,
and if necessary decrement it after finishing all checks.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
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>
This commit is contained in:
Christoph Hellwig 2014-01-22 15:29:29 +01:00
parent 7ae65c0f96
commit 7466501608
9 changed files with 69 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/scsi/advansys.c
View File

@ -2512,7 +2512,7 @@ static void asc_prt_scsi_host(struct Scsi_Host *s)
printk("Scsi_Host at addr 0x%p, device %s\n", s, dev_name(boardp->dev));
printk(" host_busy %u, host_no %d,\n",
s->host_busy, s->host_no);
atomic_read(&s->host_busy), s->host_no);
printk(" base 0x%lx, io_port 0x%lx, irq %d,\n",
(ulong)s->base, (ulong)s->io_port, boardp->irq);
@ -3346,7 +3346,7 @@ static void asc_prt_driver_conf(struct seq_file *m, struct Scsi_Host *shost)
seq_printf(m,
" host_busy %u, max_id %u, max_lun %llu, max_channel %u\n",
shost->host_busy, shost->max_id,
atomic_read(&shost->host_busy), shost->max_id,
shost->max_lun, shost->max_channel);
seq_printf(m,

4
drivers/scsi/libiscsi.c
View File

@ -2971,7 +2971,7 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
*/
for (;;) {
spin_lock_irqsave(session->host->host_lock, flags);
if (!session->host->host_busy) { /* OK for ERL == 0 */
if (!atomic_read(&session->host->host_busy)) { /* OK for ERL == 0 */
spin_unlock_irqrestore(session->host->host_lock, flags);
break;
}
@ -2979,7 +2979,7 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
msleep_interruptible(500);
iscsi_conn_printk(KERN_INFO, conn, "iscsi conn_destroy(): "
"host_busy %d host_failed %d\n",
session->host->host_busy,
atomic_read(&session->host->host_busy),
session->host->host_failed);
/*
* force eh_abort() to unblock

5
drivers/scsi/libsas/sas_scsi_host.c
View File

@ -813,7 +813,7 @@ retry:
spin_unlock_irq(shost->host_lock);
SAS_DPRINTK("Enter %s busy: %d failed: %d\n",
__func__, shost->host_busy, shost->host_failed);
__func__, atomic_read(&shost->host_busy), shost->host_failed);
/*
* Deal with commands that still have SAS tasks (i.e. they didn't
* complete via the normal sas_task completion mechanism),
@ -858,7 +858,8 @@ out:
goto retry;
SAS_DPRINTK("--- Exit %s: busy: %d failed: %d tries: %d\n",
__func__, shost->host_busy, shost->host_failed, tries);
__func__, atomic_read(&shost->host_busy),
shost->host_failed, tries);
}
enum blk_eh_timer_return sas_scsi_timed_out(struct scsi_cmnd *cmd)

2
drivers/scsi/qlogicpti.c
View File

@ -959,7 +959,7 @@ static inline void update_can_queue(struct Scsi_Host *host, u_int in_ptr, u_int
/* Temporary workaround until bug is found and fixed (one bug has been found
already, but fixing it makes things even worse) -jj */
int num_free = QLOGICPTI_REQ_QUEUE_LEN - REQ_QUEUE_DEPTH(in_ptr, out_ptr) - 64;
host->can_queue = host->host_busy + num_free;
host->can_queue = atomic_read(&host->host_busy) + num_free;
host->sg_tablesize = QLOGICPTI_MAX_SG(num_free);
}

2
drivers/scsi/scsi.c
View File

@ -600,7 +600,7 @@ void scsi_log_completion(struct scsi_cmnd *cmd, int disposition)
if (level > 3)
scmd_printk(KERN_INFO, cmd,
"scsi host busy %d failed %d\n",
cmd->device->host->host_busy,
atomic_read(&cmd->device->host->host_busy),
cmd->device->host->host_failed);
}
}

7
drivers/scsi/scsi_error.c
View File

@ -59,7 +59,7 @@ static int scsi_try_to_abort_cmd(struct scsi_host_template *,
/* called with shost->host_lock held */
void scsi_eh_wakeup(struct Scsi_Host *shost)
{
if (shost->host_busy == shost->host_failed) {
if (atomic_read(&shost->host_busy) == shost->host_failed) {
trace_scsi_eh_wakeup(shost);
wake_up_process(shost->ehandler);
SCSI_LOG_ERROR_RECOVERY(5, shost_printk(KERN_INFO, shost,
@ -2164,7 +2164,7 @@ int scsi_error_handler(void *data)
while (!kthread_should_stop()) {
set_current_state(TASK_INTERRUPTIBLE);
if ((shost->host_failed == 0 && shost->host_eh_scheduled == 0) ||
shost->host_failed != shost->host_busy) {
shost->host_failed != atomic_read(&shost->host_busy)) {
SCSI_LOG_ERROR_RECOVERY(1,
shost_printk(KERN_INFO, shost,
"scsi_eh_%d: sleeping\n",
@ -2178,7 +2178,8 @@ int scsi_error_handler(void *data)
shost_printk(KERN_INFO, shost,
"scsi_eh_%d: waking up %d/%d/%d\n",
shost->host_no, shost->host_eh_scheduled,
shost->host_failed, shost->host_busy));
shost->host_failed,
atomic_read(&shost->host_busy)));
/*
* We have a host that is failing for some reason. Figure out

74
drivers/scsi/scsi_lib.c
View File

@ -292,14 +292,17 @@ void scsi_device_unbusy(struct scsi_device *sdev)
struct scsi_target *starget = scsi_target(sdev);
unsigned long flags;
spin_lock_irqsave(shost->host_lock, flags);
shost->host_busy--;
atomic_dec(&shost->host_busy);
atomic_dec(&starget->target_busy);
if (unlikely(scsi_host_in_recovery(shost) &&
(shost->host_failed || shost->host_eh_scheduled)))
(shost->host_failed || shost->host_eh_scheduled))) {
spin_lock_irqsave(shost->host_lock, flags);
scsi_eh_wakeup(shost);
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
spin_unlock_irqrestore(shost->host_lock, flags);
}
spin_lock_irqsave(sdev->request_queue->queue_lock, flags);
sdev->device_busy--;
spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
}
@ -367,7 +370,8 @@ static inline int scsi_target_is_busy(struct scsi_target *starget)
static inline int scsi_host_is_busy(struct Scsi_Host *shost)
{
if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
if ((shost->can_queue > 0 &&
atomic_read(&shost->host_busy) >= shost->can_queue) ||
shost->host_blocked || shost->host_self_blocked)
return 1;
@ -1334,38 +1338,54 @@ static inline int scsi_host_queue_ready(struct request_queue *q,
struct Scsi_Host *shost,
struct scsi_device *sdev)
{
int ret = 0;
spin_lock_irq(shost->host_lock);
unsigned int busy;
if (scsi_host_in_recovery(shost))
goto out;
if (shost->host_busy == 0 && shost->host_blocked) {
return 0;
busy = atomic_inc_return(&shost->host_busy) - 1;
if (shost->host_blocked) {
if (busy)
goto starved;
/*
* unblock after host_blocked iterates to zero
*/
if (--shost->host_blocked != 0)
goto out;
spin_lock_irq(shost->host_lock);
if (--shost->host_blocked != 0) {
spin_unlock_irq(shost->host_lock);
goto out_dec;
}
spin_unlock_irq(shost->host_lock);
SCSI_LOG_MLQUEUE(3,
shost_printk(KERN_INFO, shost,
"unblocking host at zero depth\n"));
}
if (scsi_host_is_busy(shost)) {
if (list_empty(&sdev->starved_entry))
list_add_tail(&sdev->starved_entry, &shost->starved_list);
goto out;
}
if (shost->can_queue > 0 && busy >= shost->can_queue)
goto starved;
if (shost->host_self_blocked)
goto starved;
/* We're OK to process the command, so we can't be starved */
if (!list_empty(&sdev->starved_entry))
list_del_init(&sdev->starved_entry);
if (!list_empty(&sdev->starved_entry)) {
spin_lock_irq(shost->host_lock);
if (!list_empty(&sdev->starved_entry))
list_del_init(&sdev->starved_entry);
spin_unlock_irq(shost->host_lock);
}
shost->host_busy++;
ret = 1;
out:
return 1;
starved:
spin_lock_irq(shost->host_lock);
if (list_empty(&sdev->starved_entry))
list_add_tail(&sdev->starved_entry, &shost->starved_list);
spin_unlock_irq(shost->host_lock);
return ret;
out_dec:
atomic_dec(&shost->host_busy);
return 0;
}
/*
@ -1429,12 +1449,8 @@ static void scsi_kill_request(struct request *req, struct request_queue *q)
* with the locks as normal issue path does.
*/
sdev->device_busy++;
spin_unlock(sdev->request_queue->queue_lock);
spin_lock(shost->host_lock);
shost->host_busy++;
atomic_inc(&shost->host_busy);
atomic_inc(&starget->target_busy);
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
blk_complete_request(req);
}

9
drivers/scsi/scsi_sysfs.c
View File

@ -334,7 +334,6 @@ store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline);
shost_rd_attr(unique_id, "%u\n");
shost_rd_attr(host_busy, "%hu\n");
shost_rd_attr(cmd_per_lun, "%hd\n");
shost_rd_attr(can_queue, "%hd\n");
shost_rd_attr(sg_tablesize, "%hu\n");
@ -344,6 +343,14 @@ shost_rd_attr(prot_capabilities, "%u\n");
shost_rd_attr(prot_guard_type, "%hd\n");
shost_rd_attr2(proc_name, hostt->proc_name, "%s\n");
static ssize_t
show_host_busy(struct device *dev, struct device_attribute *attr, char *buf)
{
struct Scsi_Host *shost = class_to_shost(dev);
return snprintf(buf, 20, "%d\n", atomic_read(&shost->host_busy));
}
static DEVICE_ATTR(host_busy, S_IRUGO, show_host_busy, NULL);
static struct attribute *scsi_sysfs_shost_attrs[] = {
&dev_attr_unique_id.attr,
&dev_attr_host_busy.attr,

10
include/scsi/scsi_host.h
View File

@ -582,13 +582,9 @@ struct Scsi_Host {
*/
struct blk_queue_tag *bqt;
/*
* The following two fields are protected with host_lock;
* however, eh routines can safely access during eh processing
* without acquiring the lock.
*/
unsigned int host_busy; /* commands actually active on low-level */
unsigned int host_failed; /* commands that failed. */
atomic_t host_busy; /* commands actually active on low-level */
unsigned int host_failed; /* commands that failed.
protected by host_lock */
unsigned int host_eh_scheduled; /* EH scheduled without command */
unsigned int host_no; /* Used for IOCTL_GET_IDLUN, /proc/scsi et al. */