Re: [PATCH 16/17] tcmu: make ring buffer timer configurable

[Mike Christie <mchristi@redhat.com>]

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On 10/18/2017 02:14 AM, Mike Christie wrote:
> 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.
> 

Sent a bad patch. This version of the patch had a bug when
cmd_time_out=0 and qfull_time_out > 0. I have attached a version 2 which
fixes this.





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From 8830f5f390181125e1e614f19e0c48524da31bb9 Mon Sep 17 00:00:00 2001
From: Mike Christie <mchristi@redhat.com>
Date: Wed, 18 Oct 2017 03:02:22 -0500
Subject: [PATCH] tcmu: make ring buffer timer configurable v2

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.

v2:
Fix bug where if cmd_time_out=0 and qfull_time_out > 0
then inflight commands might timeout after qfull_time_out secs.
---
 drivers/target/target_core_user.c | 104 +++++++++++++++++++++++++++++---------
 1 file changed, 81 insertions(+), 23 deletions(-)

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 09d0b5b..f9f0677 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;
+	unsigned int qfull_time_out;
+
 	struct list_head timedout_entry;
 
 	spinlock_t nl_cmd_lock;
@@ -766,18 +770,14 @@ 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) {
@@ -786,14 +786,15 @@ 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;
 }
 
@@ -802,7 +803,8 @@ static int add_to_cmdr_queue(struct tcmu_cmd *tcmu_cmd)
 	struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
 	int ret;
 
-	ret = tcmu_setup_cmd_timer(tcmu_cmd);
+	ret = tcmu_setup_cmd_timer(tcmu_cmd, udev->qfull_time_out,
+				   &udev->qfull_timer);
 	if (ret)
 		return ret;
 
@@ -938,7 +940,8 @@ 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);
 		*scsi_err = TCM_OUT_OF_RESOURCES;
@@ -971,6 +974,11 @@ static sense_reason_t queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, int *scsi_err)
 	return 0;
 
 queue:
+	if (!udev->qfull_time_out) {
+		*scsi_err = TCM_OUT_OF_RESOURCES;
+		return -1;
+	}
+
 	if (add_to_cmdr_queue(tcmu_cmd)) {
 		*scsi_err = TCM_OUT_OF_RESOURCES;
 		return -1;
@@ -1085,7 +1093,7 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 	}
 
 	if (mb->cmd_tail == mb->cmd_head && list_empty(&udev->cmdr_queue))
-		del_timer(&udev->timeout); /* no more pending or waiting cmds */
+		del_timer(&udev->cmd_timer); /* no more pending or waiting cmds */
 
 	return handled;
 }
@@ -1105,13 +1113,15 @@ 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
@@ -1131,6 +1141,12 @@ 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;
 }
@@ -1139,7 +1155,7 @@ static void tcmu_device_timedout(unsigned long data)
 {
 	struct tcmu_dev *udev = (struct tcmu_dev *)data;
 
-	pr_debug("%s cmd timeout has expired\n", udev->name);
+	pr_debug("%s cmd/qfull timeout has expired\n", udev->name);
 
 	spin_lock(&timed_out_udevs_lock);
 	if (list_empty(&udev->timedout_entry))
@@ -1186,6 +1202,8 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 
 	udev->hba = hba;
 	udev->cmd_time_out = TCMU_TIME_OUT;
+	/* for backwards compat use the cmd_time_out */
+	udev->qfull_time_out = TCMU_TIME_OUT;
 
 	mutex_init(&udev->cmdr_lock);
 
@@ -1194,7 +1212,10 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 	INIT_LIST_HEAD(&udev->waiter);
 	idr_init(&udev->commands);
 
-	setup_timer(&udev->timeout, tcmu_device_timedout,
+	setup_timer(&udev->qfull_timer, tcmu_device_timedout,
+		(unsigned long)udev);
+
+	setup_timer(&udev->cmd_timer, tcmu_device_timedout,
 		(unsigned long)udev);
 
 	init_waitqueue_head(&udev->nl_cmd_wq);
@@ -1250,6 +1271,8 @@ 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;
 }
@@ -1777,7 +1800,8 @@ 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);
@@ -1962,6 +1986,39 @@ 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, "%lu\n",
+			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),
@@ -2107,6 +2164,7 @@ static ssize_t tcmu_emulate_write_cache_store(struct config_item *item,
 
 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,
-- 
1.8.3.1