tcmu: make ring buffer timer configurable

This adds a timer, qfull_time_out, that controls how long a
device will wait for ring buffer space to open before
failing the commands in the queue. It is useful to separate
this timer from the cmd_time_out and default 30 sec one,
because for HA setups cmd_time_out may be disbled and 30
seconds is too long to wait when some OSs like ESX will
timeout commands after as little as 8 - 15 seconds.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 115 insertions, 34 deletions

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 52fc1d440d23..c6a0c3198ccc 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -142,8 +142,12 @@ struct tcmu_dev {
 
         struct idr commands;
 
-        struct timer_list timeout;
+        struct timer_list cmd_timer;
         unsigned int cmd_time_out;
+
+        struct timer_list qfull_timer;
+        int qfull_time_out;
+
         struct list_head timedout_entry;
 
         spinlock_t nl_cmd_lock;
@@ -741,18 +745,14 @@ static inline size_t tcmu_cmd_get_cmd_size(struct tcmu_cmd *tcmu_cmd,
         return command_size;
 }
 
-static int tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd)
+static int tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd, unsigned int tmo,
+                                struct timer_list *timer)
 {
         struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
-        unsigned long tmo = udev->cmd_time_out;
         int cmd_id;
 
-        /*
-         * If it was on the cmdr queue waiting we do not reset the timer
-         * for requeues and when it is finally sent to userspace.
-         */
         if (tcmu_cmd->cmd_id)
-                return 0;
+                goto setup_timer;
 
         cmd_id = idr_alloc(&udev->commands, tcmu_cmd, 1, USHRT_MAX, GFP_NOWAIT);
         if (cmd_id < 0) {
@@ -761,23 +761,38 @@ static int tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd)
         }
         tcmu_cmd->cmd_id = cmd_id;
 
-        if (!tmo)
-                tmo = TCMU_TIME_OUT;
-
         pr_debug("allocated cmd %u for dev %s tmo %lu\n", tcmu_cmd->cmd_id,
                  udev->name, tmo / MSEC_PER_SEC);
 
+setup_timer:
+        if (!tmo)
+                return 0;
+
         tcmu_cmd->deadline = round_jiffies_up(jiffies + msecs_to_jiffies(tmo));
-        mod_timer(&udev->timeout, tcmu_cmd->deadline);
+        mod_timer(timer, tcmu_cmd->deadline);
         return 0;
 }
 
 static int add_to_cmdr_queue(struct tcmu_cmd *tcmu_cmd)
 {
         struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
+        unsigned int tmo;
         int ret;
 
-        ret = tcmu_setup_cmd_timer(tcmu_cmd);
+        /*
+         * For backwards compat if qfull_time_out is not set use
+         * cmd_time_out and if that's not set use the default time out.
+         */
+        if (!udev->qfull_time_out)
+                return -ETIMEDOUT;
+        else if (udev->qfull_time_out > 0)
+                tmo = udev->qfull_time_out;
+        else if (udev->cmd_time_out)
+                tmo = udev->cmd_time_out;
+        else
+                tmo = TCMU_TIME_OUT;
+
+        ret = tcmu_setup_cmd_timer(tcmu_cmd, tmo, &udev->qfull_timer);
         if (ret)
                 return ret;
 
@@ -901,7 +916,8 @@ static sense_reason_t queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, int *scsi_err)
         }
         entry->req.iov_bidi_cnt = iov_cnt;
 
-        ret = tcmu_setup_cmd_timer(tcmu_cmd);
+        ret = tcmu_setup_cmd_timer(tcmu_cmd, udev->cmd_time_out,
+                                   &udev->cmd_timer);
         if (ret) {
                 tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
                 mutex_unlock(&udev->cmdr_lock);
@@ -1049,14 +1065,19 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
                 handled++;
         }
 
-        if (mb->cmd_tail == mb->cmd_head && list_empty(&udev->cmdr_queue)) {
-                del_timer(&udev->timeout);
-                /*
-                 * not more pending or waiting commands so try to reclaim
-                 * blocks if needed.
-                 */
-                if (atomic_read(&global_db_count) > TCMU_GLOBAL_MAX_BLOCKS)
-                        schedule_delayed_work(&tcmu_unmap_work, 0);
+        if (mb->cmd_tail == mb->cmd_head) {
+                /* no more pending commands */
+                del_timer(&udev->cmd_timer);
+
+                if (list_empty(&udev->cmdr_queue)) {
+                        /*
+                         * no more pending or waiting commands so try to
+                         * reclaim blocks if needed.
+                         */
+                        if (atomic_read(&global_db_count) >
+                            TCMU_GLOBAL_MAX_BLOCKS)
+                                schedule_delayed_work(&tcmu_unmap_work, 0);
+                }
         }
 
         return handled;
@@ -1077,13 +1098,15 @@ static int tcmu_check_expired_cmd(int id, void *p, void *data)
                 return 0;
 
         is_running = list_empty(&cmd->cmdr_queue_entry);
-        pr_debug("Timing out cmd %u on dev %s that is %s.\n",
-                 id, udev->name, is_running ? "inflight" : "queued");
-
-        se_cmd = cmd->se_cmd;
-        cmd->se_cmd = NULL;
 
         if (is_running) {
+                /*
+                 * If cmd_time_out is disabled but qfull is set deadline
+                 * will only reflect the qfull timeout. Ignore it.
+                 */
+                if (!udev->cmd_time_out)
+                        return 0;
+
                 set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
                 /*
                  * target_complete_cmd will translate this to LUN COMM FAILURE
@@ -1096,16 +1119,18 @@ static int tcmu_check_expired_cmd(int id, void *p, void *data)
                 tcmu_free_cmd(cmd);
                 scsi_status = SAM_STAT_TASK_SET_FULL;
         }
+
+        pr_debug("Timing out cmd %u on dev %s that is %s.\n",
+                 id, udev->name, is_running ? "inflight" : "queued");
+
+        se_cmd = cmd->se_cmd;
+        cmd->se_cmd = NULL;
         target_complete_cmd(se_cmd, scsi_status);
         return 0;
 }
 
-static void tcmu_device_timedout(struct timer_list *t)
+static void tcmu_device_timedout(struct tcmu_dev *udev)
 {
-        struct tcmu_dev *udev = from_timer(udev, t, timeout);
-
-        pr_debug("%s cmd timeout has expired\n", udev->name);
-
         spin_lock(&timed_out_udevs_lock);
         if (list_empty(&udev->timedout_entry))
                 list_add_tail(&udev->timedout_entry, &timed_out_udevs);
@@ -1114,6 +1139,22 @@ static void tcmu_device_timedout(struct timer_list *t)
         schedule_delayed_work(&tcmu_unmap_work, 0);
 }
 
+static void tcmu_cmd_timedout(struct timer_list *t)
+{
+        struct tcmu_dev *udev = from_timer(udev, t, cmd_timer);
+
+        pr_debug("%s cmd timeout has expired\n", udev->name);
+        tcmu_device_timedout(udev);
+}
+
+static void tcmu_qfull_timedout(struct timer_list *t)
+{
+        struct tcmu_dev *udev = from_timer(udev, t, qfull_timer);
+
+        pr_debug("%s qfull timeout has expired\n", udev->name);
+        tcmu_device_timedout(udev);
+}
+
 static int tcmu_attach_hba(struct se_hba *hba, u32 host_id)
 {
         struct tcmu_hba *tcmu_hba;
@@ -1151,6 +1192,7 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 
         udev->hba = hba;
         udev->cmd_time_out = TCMU_TIME_OUT;
+        udev->qfull_time_out = -1;
 
         mutex_init(&udev->cmdr_lock);
 
@@ -1158,7 +1200,8 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
         INIT_LIST_HEAD(&udev->cmdr_queue);
         idr_init(&udev->commands);
 
-        timer_setup(&udev->timeout, tcmu_device_timedout, 0);
+        timer_setup(&udev->qfull_timer, tcmu_qfull_timedout, 0);
+        timer_setup(&udev->cmd_timer, tcmu_cmd_timedout, 0);
 
         init_waitqueue_head(&udev->nl_cmd_wq);
         spin_lock_init(&udev->nl_cmd_lock);
@@ -1213,6 +1256,8 @@ static bool run_cmdr_queue(struct tcmu_dev *udev)
                         goto done;
                 }
         }
+        if (list_empty(&udev->cmdr_queue))
+                del_timer(&udev->qfull_timer);
 done:
         return drained;
 }
@@ -1712,7 +1757,8 @@ static void tcmu_destroy_device(struct se_device *dev)
 {
         struct tcmu_dev *udev = TCMU_DEV(dev);
 
-        del_timer_sync(&udev->timeout);
+        del_timer_sync(&udev->cmd_timer);
+        del_timer_sync(&udev->qfull_timer);
 
         mutex_lock(&root_udev_mutex);
         list_del(&udev->node);
@@ -1893,6 +1939,40 @@ static ssize_t tcmu_cmd_time_out_store(struct config_item *item, const char *pag
 }
 CONFIGFS_ATTR(tcmu_, cmd_time_out);
 
+static ssize_t tcmu_qfull_time_out_show(struct config_item *item, char *page)
+{
+        struct se_dev_attrib *da = container_of(to_config_group(item),
+                                                struct se_dev_attrib, da_group);
+        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
+
+        return snprintf(page, PAGE_SIZE, "%ld\n", udev->qfull_time_out <= 0 ?
+                        udev->qfull_time_out :
+                        udev->qfull_time_out / MSEC_PER_SEC);
+}
+
+static ssize_t tcmu_qfull_time_out_store(struct config_item *item,
+                                         const char *page, size_t count)
+{
+        struct se_dev_attrib *da = container_of(to_config_group(item),
+                                        struct se_dev_attrib, da_group);
+        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
+        s32 val;
+        int ret;
+
+        ret = kstrtos32(page, 0, &val);
+        if (ret < 0)
+                return ret;
+
+        if (val >= 0) {
+                udev->qfull_time_out = val * MSEC_PER_SEC;
+        } else {
+                printk(KERN_ERR "Invalid qfull timeout value %d\n", val);
+                return -EINVAL;
+        }
+        return count;
+}
+CONFIGFS_ATTR(tcmu_, qfull_time_out);
+
 static ssize_t tcmu_dev_config_show(struct config_item *item, char *page)
 {
         struct se_dev_attrib *da = container_of(to_config_group(item),
@@ -2038,6 +2118,7 @@ CONFIGFS_ATTR(tcmu_, emulate_write_cache);
 
 static struct configfs_attribute *tcmu_attrib_attrs[] = {
         &tcmu_attr_cmd_time_out,
+        &tcmu_attr_qfull_time_out,
         &tcmu_attr_dev_config,
         &tcmu_attr_dev_size,
         &tcmu_attr_emulate_write_cache,