scsi_dh_alua: Use workqueue for RTPG
The current ALUA device_handler has two drawbacks:
- We're sending a 'SET TARGET PORT GROUP' command to every LUN,
disregarding the fact that several LUNs might be in a port group
and will be automatically switched whenever _any_ LUN within
that port group receives the command.
- Whenever a LUN is in 'transitioning' mode we cannot block I/O
to that LUN, instead the controller has to abort the command.
This leads to increased traffic across the wire and heavy load
on the controller during switchover.
With this patch the RTPG handling is moved to a per-portgroup
workqueue. This reduces the number of 'REPORT TARGET PORT GROUP'
and 'SET TARGET PORT GROUPS' sent to the controller as we're sending
them now per port group, and not per device as previously.
It also allows us to block I/O to any LUN / port group found to be
in 'transitioning' ALUA mode, as the workqueue item will be requeued
until the controller moves out of transitioning.
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 7a351cf..8318852 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -59,10 +59,15 @@
#define ALUA_RTPG_SIZE 128
#define ALUA_FAILOVER_TIMEOUT 60
#define ALUA_FAILOVER_RETRIES 5
+#define ALUA_RTPG_DELAY_MSECS 5
/* device handler flags */
-#define ALUA_OPTIMIZE_STPG 1
-#define ALUA_RTPG_EXT_HDR_UNSUPP 2
+#define ALUA_OPTIMIZE_STPG 0x01
+#define ALUA_RTPG_EXT_HDR_UNSUPP 0x02
+/* State machine flags */
+#define ALUA_PG_RUN_RTPG 0x10
+#define ALUA_PG_RUN_STPG 0x20
+#define ALUA_PG_RUNNING 0x40
static uint optimize_stpg;
module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
@@ -70,9 +75,11 @@
static LIST_HEAD(port_group_list);
static DEFINE_SPINLOCK(port_group_lock);
+static struct workqueue_struct *kaluad_wq;
struct alua_port_group {
struct kref kref;
+ struct rcu_head rcu;
struct list_head node;
unsigned char device_id_str[256];
int device_id_len;
@@ -82,12 +89,25 @@
int pref;
unsigned flags; /* used for optimizing STPG */
unsigned char transition_tmo;
+ unsigned long expiry;
+ unsigned long interval;
+ struct delayed_work rtpg_work;
+ spinlock_t lock;
+ struct list_head rtpg_list;
+ struct scsi_device *rtpg_sdev;
};
struct alua_dh_data {
struct alua_port_group *pg;
int group_id;
+ spinlock_t pg_lock;
struct scsi_device *sdev;
+ int init_error;
+ struct mutex init_mutex;
+};
+
+struct alua_queue_data {
+ struct list_head entry;
activate_complete callback_fn;
void *callback_data;
};
@@ -95,18 +115,22 @@
#define ALUA_POLICY_SWITCH_CURRENT 0
#define ALUA_POLICY_SWITCH_ALL 1
-static int alua_rtpg(struct scsi_device *, struct alua_port_group *);
-static char print_alua_state(int);
+static void alua_rtpg_work(struct work_struct *work);
+static void alua_rtpg_queue(struct alua_port_group *pg,
+ struct scsi_device *sdev,
+ struct alua_queue_data *qdata);
static void release_port_group(struct kref *kref)
{
struct alua_port_group *pg;
pg = container_of(kref, struct alua_port_group, kref);
+ if (pg->rtpg_sdev)
+ flush_delayed_work(&pg->rtpg_work);
spin_lock(&port_group_lock);
list_del(&pg->node);
spin_unlock(&port_group_lock);
- kfree(pg);
+ kfree_rcu(pg, rcu);
}
/*
@@ -225,6 +249,10 @@
if (optimize_stpg)
pg->flags |= ALUA_OPTIMIZE_STPG;
kref_init(&pg->kref);
+ INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
+ INIT_LIST_HEAD(&pg->rtpg_list);
+ INIT_LIST_HEAD(&pg->node);
+ spin_lock_init(&pg->lock);
spin_lock(&port_group_lock);
tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
@@ -304,6 +332,7 @@
int tpgs)
{
int rel_port = -1, group_id;
+ struct alua_port_group *pg, *old_pg = NULL;
group_id = scsi_vpd_tpg_id(sdev, &rel_port);
if (group_id < 0) {
@@ -318,18 +347,30 @@
return SCSI_DH_DEV_UNSUPP;
}
- h->pg = alua_alloc_pg(sdev, group_id, tpgs);
- if (IS_ERR(h->pg)) {
- if (PTR_ERR(h->pg) == -ENOMEM)
+ pg = alua_alloc_pg(sdev, group_id, tpgs);
+ if (IS_ERR(pg)) {
+ if (PTR_ERR(pg) == -ENOMEM)
return SCSI_DH_NOMEM;
return SCSI_DH_DEV_UNSUPP;
}
sdev_printk(KERN_INFO, sdev,
"%s: device %s port group %x rel port %x\n",
- ALUA_DH_NAME, h->pg->device_id_str,
- h->group_id, rel_port);
+ ALUA_DH_NAME, pg->device_id_str, group_id, rel_port);
- return alua_rtpg(sdev, h->pg);
+ /* Check for existing port group references */
+ spin_lock(&h->pg_lock);
+ old_pg = h->pg;
+ if (old_pg != pg) {
+ /* port group has changed. Update to new port group */
+ rcu_assign_pointer(h->pg, pg);
+ }
+ alua_rtpg_queue(h->pg, sdev, NULL);
+ spin_unlock(&h->pg_lock);
+
+ if (old_pg)
+ kref_put(&old_pg->kref, release_port_group);
+
+ return SCSI_DH_OK;
}
static char print_alua_state(int state)
@@ -423,14 +464,17 @@
int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
unsigned char *ucp, *buff;
unsigned err, retval;
- unsigned long expiry, interval = 0;
unsigned int tpg_desc_tbl_off;
unsigned char orig_transition_tmo;
- if (!pg->transition_tmo)
- expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
- else
- expiry = round_jiffies_up(jiffies + pg->transition_tmo * HZ);
+ if (!pg->expiry) {
+ unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
+
+ if (pg->transition_tmo)
+ transition_tmo = pg->transition_tmo * HZ;
+
+ pg->expiry = round_jiffies_up(jiffies + transition_tmo);
+ }
buff = kzalloc(bufflen, GFP_KERNEL);
if (!buff)
@@ -473,16 +517,18 @@
err = SCSI_DH_RETRY;
else if (sense_hdr.sense_key == UNIT_ATTENTION)
err = SCSI_DH_RETRY;
- if (err == SCSI_DH_RETRY && time_before(jiffies, expiry)) {
+ if (err == SCSI_DH_RETRY &&
+ pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
ALUA_DH_NAME);
scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
- goto retry;
+ return err;
}
sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
ALUA_DH_NAME);
scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
kfree(buff);
+ pg->expiry = 0;
return SCSI_DH_IO;
}
@@ -497,6 +543,7 @@
sdev_printk(KERN_WARNING, sdev,
"%s: kmalloc buffer failed\n",__func__);
/* Temporary failure, bypass */
+ pg->expiry = 0;
return SCSI_DH_DEV_TEMP_BUSY;
}
goto retry;
@@ -512,7 +559,7 @@
sdev_printk(KERN_INFO, sdev,
"%s: transition timeout set to %d seconds\n",
ALUA_DH_NAME, pg->transition_tmo);
- expiry = jiffies + pg->transition_tmo * HZ;
+ pg->expiry = jiffies + pg->transition_tmo * HZ;
}
if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
@@ -546,23 +593,26 @@
switch (pg->state) {
case TPGS_STATE_TRANSITIONING:
- if (time_before(jiffies, expiry)) {
+ if (time_before(jiffies, pg->expiry)) {
/* State transition, retry */
- interval += 2000;
- msleep(interval);
- goto retry;
+ pg->interval = 2;
+ err = SCSI_DH_RETRY;
+ } else {
+ /* Transitioning time exceeded, set port to standby */
+ err = SCSI_DH_IO;
+ pg->state = TPGS_STATE_STANDBY;
+ pg->expiry = 0;
}
- /* Transitioning time exceeded, set port to standby */
- err = SCSI_DH_RETRY;
- pg->state = TPGS_STATE_STANDBY;
break;
case TPGS_STATE_OFFLINE:
/* Path unusable */
err = SCSI_DH_DEV_OFFLINED;
+ pg->expiry = 0;
break;
default:
/* Useable path if active */
err = SCSI_DH_OK;
+ pg->expiry = 0;
break;
}
kfree(buff);
@@ -627,6 +677,107 @@
return SCSI_DH_RETRY;
}
+static void alua_rtpg_work(struct work_struct *work)
+{
+ struct alua_port_group *pg =
+ container_of(work, struct alua_port_group, rtpg_work.work);
+ struct scsi_device *sdev;
+ LIST_HEAD(qdata_list);
+ int err = SCSI_DH_OK;
+ struct alua_queue_data *qdata, *tmp;
+ unsigned long flags;
+
+ spin_lock_irqsave(&pg->lock, flags);
+ sdev = pg->rtpg_sdev;
+ if (!sdev) {
+ WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
+ WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
+ spin_unlock_irqrestore(&pg->lock, flags);
+ return;
+ }
+ pg->flags |= ALUA_PG_RUNNING;
+ if (pg->flags & ALUA_PG_RUN_RTPG) {
+ pg->flags &= ~ALUA_PG_RUN_RTPG;
+ spin_unlock_irqrestore(&pg->lock, flags);
+ err = alua_rtpg(sdev, pg);
+ spin_lock_irqsave(&pg->lock, flags);
+ if (err == SCSI_DH_RETRY) {
+ pg->flags &= ~ALUA_PG_RUNNING;
+ pg->flags |= ALUA_PG_RUN_RTPG;
+ spin_unlock_irqrestore(&pg->lock, flags);
+ queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+ pg->interval * HZ);
+ return;
+ }
+ if (err != SCSI_DH_OK)
+ pg->flags &= ~ALUA_PG_RUN_STPG;
+ }
+ if (pg->flags & ALUA_PG_RUN_STPG) {
+ pg->flags &= ~ALUA_PG_RUN_STPG;
+ spin_unlock_irqrestore(&pg->lock, flags);
+ err = alua_stpg(sdev, pg);
+ spin_lock_irqsave(&pg->lock, flags);
+ if (err == SCSI_DH_RETRY) {
+ pg->flags |= ALUA_PG_RUN_RTPG;
+ pg->interval = 0;
+ pg->flags &= ~ALUA_PG_RUNNING;
+ spin_unlock_irqrestore(&pg->lock, flags);
+ queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+ pg->interval * HZ);
+ return;
+ }
+ }
+
+ list_splice_init(&pg->rtpg_list, &qdata_list);
+ pg->rtpg_sdev = NULL;
+ spin_unlock_irqrestore(&pg->lock, flags);
+
+ list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
+ list_del(&qdata->entry);
+ if (qdata->callback_fn)
+ qdata->callback_fn(qdata->callback_data, err);
+ kfree(qdata);
+ }
+ spin_lock_irqsave(&pg->lock, flags);
+ pg->flags &= ~ALUA_PG_RUNNING;
+ spin_unlock_irqrestore(&pg->lock, flags);
+ scsi_device_put(sdev);
+ kref_put(&pg->kref, release_port_group);
+}
+
+static void alua_rtpg_queue(struct alua_port_group *pg,
+ struct scsi_device *sdev,
+ struct alua_queue_data *qdata)
+{
+ int start_queue = 0;
+ unsigned long flags;
+
+ if (!pg)
+ return;
+
+ spin_lock_irqsave(&pg->lock, flags);
+ if (qdata) {
+ list_add_tail(&qdata->entry, &pg->rtpg_list);
+ pg->flags |= ALUA_PG_RUN_STPG;
+ }
+ if (pg->rtpg_sdev == NULL) {
+ pg->interval = 0;
+ pg->flags |= ALUA_PG_RUN_RTPG;
+ kref_get(&pg->kref);
+ pg->rtpg_sdev = sdev;
+ scsi_device_get(sdev);
+ start_queue = 1;
+ }
+ spin_unlock_irqrestore(&pg->lock, flags);
+
+ if (start_queue &&
+ !queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+ msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS))) {
+ scsi_device_put(sdev);
+ kref_put(&pg->kref, release_port_group);
+ }
+}
+
/*
* alua_initialize - Initialize ALUA state
* @sdev: the device to be initialized
@@ -638,10 +789,12 @@
{
int err = SCSI_DH_DEV_UNSUPP, tpgs;
+ mutex_lock(&h->init_mutex);
tpgs = alua_check_tpgs(sdev);
if (tpgs != TPGS_MODE_NONE)
err = alua_check_vpd(sdev, h, tpgs);
-
+ h->init_error = err;
+ mutex_unlock(&h->init_mutex);
return err;
}
/*
@@ -656,10 +809,11 @@
static int alua_set_params(struct scsi_device *sdev, const char *params)
{
struct alua_dh_data *h = sdev->handler_data;
- struct alua_port_group *pg = NULL;
+ struct alua_port_group __rcu *pg = NULL;
unsigned int optimize = 0, argc;
const char *p = params;
int result = SCSI_DH_OK;
+ unsigned long flags;
if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
return -EINVAL;
@@ -669,14 +823,19 @@
if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
return -EINVAL;
- pg = h->pg;
- if (!pg)
+ rcu_read_lock();
+ pg = rcu_dereference(h->pg);
+ if (!pg) {
+ rcu_read_unlock();
return -ENXIO;
-
+ }
+ spin_lock_irqsave(&pg->lock, flags);
if (optimize)
pg->flags |= ALUA_OPTIMIZE_STPG;
else
pg->flags &= ~ALUA_OPTIMIZE_STPG;
+ spin_unlock_irqrestore(&pg->lock, flags);
+ rcu_read_unlock();
return result;
}
@@ -696,21 +855,33 @@
{
struct alua_dh_data *h = sdev->handler_data;
int err = SCSI_DH_OK;
+ struct alua_queue_data *qdata;
+ struct alua_port_group __rcu *pg;
- if (!h->pg)
- goto out;
-
- kref_get(&h->pg->kref);
-
- err = alua_rtpg(sdev, h->pg);
- if (err != SCSI_DH_OK) {
- kref_put(&h->pg->kref, release_port_group);
+ qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
+ if (!qdata) {
+ err = SCSI_DH_RES_TEMP_UNAVAIL;
goto out;
}
- err = alua_stpg(sdev, h->pg);
- if (err == SCSI_DH_RETRY)
- err = alua_rtpg(sdev, h->pg);
- kref_put(&h->pg->kref, release_port_group);
+ qdata->callback_fn = fn;
+ qdata->callback_data = data;
+
+ mutex_lock(&h->init_mutex);
+ rcu_read_lock();
+ pg = rcu_dereference(h->pg);
+ if (!pg || !kref_get_unless_zero(&pg->kref)) {
+ rcu_read_unlock();
+ kfree(qdata);
+ err = h->init_error;
+ mutex_unlock(&h->init_mutex);
+ goto out;
+ }
+ fn = NULL;
+ rcu_read_unlock();
+ mutex_unlock(&h->init_mutex);
+
+ alua_rtpg_queue(pg, sdev, qdata);
+ kref_put(&pg->kref, release_port_group);
out:
if (fn)
fn(data, err);
@@ -726,14 +897,15 @@
static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
{
struct alua_dh_data *h = sdev->handler_data;
- int state;
+ struct alua_port_group __rcu *pg;
+ int state = TPGS_STATE_OPTIMIZED;
int ret = BLKPREP_OK;
- if (!h->pg)
- return ret;
- kref_get(&h->pg->kref);
- state = h->pg->state;
- kref_put(&h->pg->kref, release_port_group);
+ rcu_read_lock();
+ pg = rcu_dereference(h->pg);
+ if (pg)
+ state = pg->state;
+ rcu_read_unlock();
if (state == TPGS_STATE_TRANSITIONING)
ret = BLKPREP_DEFER;
else if (state != TPGS_STATE_OPTIMIZED &&
@@ -758,9 +930,12 @@
h = kzalloc(sizeof(*h) , GFP_KERNEL);
if (!h)
return -ENOMEM;
- h->pg = NULL;
+ spin_lock_init(&h->pg_lock);
+ rcu_assign_pointer(h->pg, NULL);
+ h->init_error = SCSI_DH_OK;
h->sdev = sdev;
+ mutex_init(&h->init_mutex);
err = alua_initialize(sdev, h);
if (err == SCSI_DH_NOMEM)
ret = -ENOMEM;
@@ -781,11 +956,16 @@
static void alua_bus_detach(struct scsi_device *sdev)
{
struct alua_dh_data *h = sdev->handler_data;
+ struct alua_port_group *pg;
- if (h->pg) {
- kref_put(&h->pg->kref, release_port_group);
- h->pg = NULL;
- }
+ spin_lock(&h->pg_lock);
+ pg = h->pg;
+ rcu_assign_pointer(h->pg, NULL);
+ h->sdev = NULL;
+ spin_unlock(&h->pg_lock);
+ if (pg)
+ kref_put(&pg->kref, release_port_group);
+
sdev->handler_data = NULL;
kfree(h);
}
@@ -805,16 +985,24 @@
{
int r;
+ kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
+ if (!kaluad_wq) {
+ /* Temporary failure, bypass */
+ return SCSI_DH_DEV_TEMP_BUSY;
+ }
r = scsi_register_device_handler(&alua_dh);
- if (r != 0)
+ if (r != 0) {
printk(KERN_ERR "%s: Failed to register scsi device handler",
ALUA_DH_NAME);
+ destroy_workqueue(kaluad_wq);
+ }
return r;
}
static void __exit alua_exit(void)
{
scsi_unregister_device_handler(&alua_dh);
+ destroy_workqueue(kaluad_wq);
}
module_init(alua_init);