[PATCH v3 01/14] libsas: introduce sas_drain_work()

Dan Williams
2012-01-06T00:59:05Z

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."

Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/scsi/aic94xx/aic94xx_init.c | 2 +
drivers/scsi/isci/host.c | 8 ++---
drivers/scsi/libsas/sas_discover.c | 21 +++++++++++++
drivers/scsi/libsas/sas_event.c | 55 +++++++++++++++++++++++++++++++++++
drivers/scsi/libsas/sas_init.c | 9 ++++--
drivers/scsi/libsas/sas_internal.h | 14 ---------
drivers/scsi/mvsas/mv_sas.c | 2 +
drivers/scsi/pm8001/pm8001_sas.c | 4 ++-
include/scsi/libsas.h | 4 +++
9 files changed, 93 insertions(+), 26 deletions(-)

diff --git a/drivers/scsi/aic94xx/aic94xx_init.c b/drivers/scsi/aic94xx/aic94xx_init.c
index 8db4e72..2b3717f 100644
--- a/drivers/scsi/aic94xx/aic94xx_init.c
+++ b/drivers/scsi/aic94xx/aic94xx_init.c
@@ -971,7 +971,7 @@ static int asd_scan_finished(struct Scsi_Host *shost, unsigned long time)
if (time < HZ)
return 0;
/* Wait for discovery to finish */
- scsi_flush_work(shost);
+ sas_drain_work(SHOST_TO_SAS_HA(shost));
return 1;
}

diff --git a/drivers/scsi/isci/host.c b/drivers/scsi/isci/host.c
index e7fe9c4..e7e5d06 100644
--- a/drivers/scsi/isci/host.c
+++ b/drivers/scsi/isci/host.c
@@ -650,15 +650,13 @@ static void isci_host_start_complete(struct isci_host *ihost, enum sci_status co

int isci_host_scan_finished(struct Scsi_Host *shost, unsigned long time)
{
- struct isci_host *ihost = SHOST_TO_SAS_HA(shost)->lldd_ha;
+ struct sas_ha_struct *ha = SHOST_TO_SAS_HA(shost);
+ struct isci_host *ihost = ha->lldd_ha;

if (test_bit(IHOST_START_PENDING, &ihost->flags))
return 0;

- /* todo: use sas_flush_discovery once it is upstream */
- scsi_flush_work(shost);
-
- scsi_flush_work(shost);
+ sas_drain_work(ha);

dev_dbg(&ihost->pdev->dev,
"%s: ihost->status = %d, time = %ld\n",
diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
index ed04118..32e0117 100644
--- a/drivers/scsi/libsas/sas_discover.c
+++ b/drivers/scsi/libsas/sas_discover.c
@@ -367,6 +367,25 @@ static void sas_revalidate_domain(struct work_struct *work)

/* ---------- Events ---------- */

+static void sas_chain_work(struct sas_ha_struct *ha, struct work_struct *work)
+{
+ /* chained work is not subject to SA_HA_DRAINING or SAS_HA_REGISTERED */
+ scsi_queue_work(ha->core.shost, work);
+}
+
+static void sas_chain_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_chain_work(ha, work);
+ spin_unlock_irqrestore(&ha->state_lock, flags);
+ }
+}
+
int sas_discover_event(struct asd_sas_port *port, enum discover_event ev)
{
struct sas_discovery *disc;
@@ -377,7 +396,7 @@ int sas_discover_event(struct asd_sas_port *port, enum discover_event ev)

BUG_ON(ev >= DISC_NUM_EVENTS);

- sas_queue_event(ev, &disc->pending, &disc->disc_work[ev].work, port->ha);
+ sas_chain_event(ev, &disc->pending, &disc->disc_work[ev].work, port->ha);

return 0;
}
diff --git a/drivers/scsi/libsas/sas_event.c b/drivers/scsi/libsas/sas_event.c
index 9c084bc..e5035aa 100644
--- a/drivers/scsi/libsas/sas_event.c
+++ b/drivers/scsi/libsas/sas_event.c
@@ -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);
diff --git a/drivers/scsi/libsas/sas_init.c b/drivers/scsi/libsas/sas_init.c
index da244e6..572b943 100644
--- a/drivers/scsi/libsas/sas_init.c
+++ b/drivers/scsi/libsas/sas_init.c
@@ -114,6 +114,8 @@ int sas_register_ha(struct sas_ha_struct *sas_ha)

set_bit(SAS_HA_REGISTERED, &sas_ha->state);
spin_lock_init(&sas_ha->state_lock);
+ mutex_init(&sas_ha->drain_mutex);
+ INIT_LIST_HEAD(&sas_ha->defer_q);

error = sas_register_phys(sas_ha);
if (error) {
@@ -157,12 +159,13 @@ int sas_unregister_ha(struct sas_ha_struct *sas_ha)
{
unsigned long flags;

- /* Set the state to unregistered to avoid further
- * events to be queued */
+ /* Set the state to unregistered to avoid further unchained
+ * events to be queued
+ */
spin_lock_irqsave(&sas_ha->state_lock, flags);
clear_bit(SAS_HA_REGISTERED, &sas_ha->state);
spin_unlock_irqrestore(&sas_ha->state_lock, flags);
- scsi_flush_work(sas_ha->core.shost);
+ sas_drain_work(sas_ha);

sas_unregister_ports(sas_ha);

diff --git a/drivers/scsi/libsas/sas_internal.h b/drivers/scsi/libsas/sas_internal.h
index 1fd84b3..948ea64 100644
--- a/drivers/scsi/libsas/sas_internal.h
+++ b/drivers/scsi/libsas/sas_internal.h
@@ -92,20 +92,6 @@ static inline int sas_smp_host_handler(struct Scsi_Host *shost,
}
#endif

-static inline void sas_queue_event(int event, unsigned long *pending,
- struct work_struct *work,
- struct sas_ha_struct *sas_ha)
-{
- if (!test_and_set_bit(event, pending)) {
- unsigned long flags;
-
- spin_lock_irqsave(&sas_ha->state_lock, flags);
- if (test_bit(SAS_HA_REGISTERED, &sas_ha->state))
- scsi_queue_work(sas_ha->core.shost, work);
- spin_unlock_irqrestore(&sas_ha->state_lock, flags);
- }
-}
-
static inline void sas_fill_in_rphy(struct domain_device *dev,
struct sas_rphy *rphy)
{
diff --git a/drivers/scsi/mvsas/mv_sas.c b/drivers/scsi/mvsas/mv_sas.c
index a4884a5..b118e63 100644
--- a/drivers/scsi/mvsas/mv_sas.c
+++ b/drivers/scsi/mvsas/mv_sas.c
@@ -308,7 +308,7 @@ int mvs_scan_finished(struct Scsi_Host *shost, unsigned long time)
if (mvs_prv->scan_finished == 0)
return 0;

- scsi_flush_work(shost);
+ sas_drain_work(sha);
return 1;
}

diff --git a/drivers/scsi/pm8001/pm8001_sas.c b/drivers/scsi/pm8001/pm8001_sas.c
index fb3dc99..13811c7 100644
--- a/drivers/scsi/pm8001/pm8001_sas.c
+++ b/drivers/scsi/pm8001/pm8001_sas.c
@@ -234,12 +234,14 @@ void pm8001_scan_start(struct Scsi_Host *shost)

int pm8001_scan_finished(struct Scsi_Host *shost, unsigned long time)
{
+ struct sas_ha_struct *ha = SHOST_TO_SAS_HA(shost);
+
/* give the phy enabling interrupt event time to come in (1s
* is empirically about all it takes) */
if (time < HZ)
return 0;
/* Wait for discovery to finish */
- scsi_flush_work(shost);
+ sas_drain_work(ha);
return 1;
}

diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index 8e402d5..42900fa 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -330,6 +330,7 @@ struct sas_ha_event {

enum sas_ha_state {
SAS_HA_REGISTERED,
+ SAS_HA_DRAINING,
};

struct sas_ha_struct {
@@ -337,6 +338,8 @@ struct sas_ha_struct {
struct sas_ha_event ha_events[HA_NUM_EVENTS];
unsigned long pending;

+ struct list_head defer_q; /* work queued while draining */
+ struct mutex drain_mutex;
unsigned long state;
spinlock_t state_lock;

@@ -657,6 +660,7 @@ int sas_eh_bus_reset_handler(struct scsi_cmnd *cmd);
extern void sas_target_destroy(struct scsi_target *);
extern int sas_slave_alloc(struct scsi_device *);
extern int sas_ioctl(struct scsi_device *sdev, int cmd, void __user *arg);
+extern int sas_drain_work(struct sas_ha_struct *ha);

extern int sas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
struct request *req);