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[SCSI] libsas: introduce sas_drain_work()

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When an lldd invokes ->notify_port_event() it can trigger a chain of libsas
events to:

  1/ form the port and find the direct attached device

  2/ if the attached device is an expander perform domain discovery

A call to flush_workqueue() will only flush the initial port formation work.
Currently libsas users need to call scsi_flush_work() up to the max depth of
chain (which will grow from 2 to 3 when ata discovery is moved to its own
discovery event).  Instead of open coding multiple calls switch to use
drain_workqueue() to flush sas work.

drain_workqueue() does not handle new work submitted during the drain so
libsas needs a bit of infrastructure to hold off unchained work submissions
while a drain is in flight.  A lldd ->notify() event is considered 'unchained'
while a sas_discover_event() is 'chained'.  As Tejun notes:

  "For now, I think it would be best to add private wrapper in libsas to
   support deferring unchained work items while draining."

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Dan Williams
2011-12-19 16:42:34 -08:00
committed by James Bottomley
parent f8daa6e6d8
commit b1124cd3ec
9 changed files with 93 additions and 26 deletions
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55
drivers/scsi/libsas/sas_event.c
View File

@@ -22,10 +22,65 @@
*
*/
#include <linux/export.h>
#include <scsi/scsi_host.h>
#include "sas_internal.h"
#include "sas_dump.h"
static void sas_queue_work(struct sas_ha_struct *ha, struct work_struct *work)
{
if (!test_bit(SAS_HA_REGISTERED, &ha->state))
return;
if (test_bit(SAS_HA_DRAINING, &ha->state))
list_add(&work->entry, &ha->defer_q);
else
scsi_queue_work(ha->core.shost, work);
}
static void sas_queue_event(int event, unsigned long *pending,
struct work_struct *work,
struct sas_ha_struct *ha)
{
if (!test_and_set_bit(event, pending)) {
unsigned long flags;
spin_lock_irqsave(&ha->state_lock, flags);
sas_queue_work(ha, work);
spin_unlock_irqrestore(&ha->state_lock, flags);
}
}
int sas_drain_work(struct sas_ha_struct *ha)
{
struct workqueue_struct *wq = ha->core.shost->work_q;
struct work_struct *w, *_w;
int err;
err = mutex_lock_interruptible(&ha->drain_mutex);
if (err)
return err;
set_bit(SAS_HA_DRAINING, &ha->state);
/* flush submitters */
spin_lock_irq(&ha->state_lock);
spin_unlock_irq(&ha->state_lock);
drain_workqueue(wq);
spin_lock_irq(&ha->state_lock);
clear_bit(SAS_HA_DRAINING, &ha->state);
list_for_each_entry_safe(w, _w, &ha->defer_q, entry) {
list_del_init(&w->entry);
sas_queue_work(ha, w);
}
spin_unlock_irq(&ha->state_lock);
mutex_unlock(&ha->drain_mutex);
return 0;
}
EXPORT_SYMBOL_GPL(sas_drain_work);
static void notify_ha_event(struct sas_ha_struct *sas_ha, enum ha_event event)
{
BUG_ON(event >= HA_NUM_EVENTS);