[v4] scsi: tcmu: avoid cmd/qfull timers updated whenever a new cmd comes

Commit Message

Xiubo Li Nov. 23, 2018, 1:15 a.m. UTC

From: Xiubo Li <[e-mail]>

Currently there has one cmd timeout timer and one qfull timer for
each udev, and whenever there has any new coming cmd it will update
the cmd timer or qfull timer. And for some corner case the timers
are always working only for the ringbuffer's and full queue's newest
cmd. That's to say the timer won't be fired even there has one cmd
stuck for a very long time and the deadline is reached.

This fix will keep the cmd/qfull timers to be pended for the oldest
cmd in ringbuffer and full queue, and will update them with the next
cmd's deadline only when the old cmd's deadline is reached or removed
from the ringbuffer and full queue.

Signed-off-by: Xiubo Li <[e-mail]>
---

Changed in V4:
- Addressed all the new comments.

Changed in V3:
- Add inflight queue support, thanks Mike.

Changed in V2:
- Add qfull timer
- Addressed all the comments from Mike, thanks.

 drivers/target/target_core_user.c | 88 +++++++++++++++++++++++++++------------
 1 file changed, 61 insertions(+), 27 deletions(-)

Comments

Mike Christie Jan. 11, 2019, 7:58 p.m. UTC | #1

On 11/22/2018 07:15 PM, [e-mail] wrote:
> From: Xiubo Li <[e-mail]>
> 
> Currently there has one cmd timeout timer and one qfull timer for
> each udev, and whenever there has any new coming cmd it will update
> the cmd timer or qfull timer. And for some corner case the timers
> are always working only for the ringbuffer's and full queue's newest
> cmd. That's to say the timer won't be fired even there has one cmd
> stuck for a very long time and the deadline is reached.
> 
> This fix will keep the cmd/qfull timers to be pended for the oldest
> cmd in ringbuffer and full queue, and will update them with the next
> cmd's deadline only when the old cmd's deadline is reached or removed
> from the ringbuffer and full queue.
> 
> Signed-off-by: Xiubo Li <[e-mail]>

Work ok for me.

Acked-by: Mike Christie <[e-mail]>

Martin K. Petersen Jan. 12, 2019, 2:06 a.m. UTC | #2

Xiubo,

> This fix will keep the cmd/qfull timers to be pended for the oldest
> cmd in ringbuffer and full queue, and will update them with the next
> cmd's deadline only when the old cmd's deadline is reached or removed
> from the ringbuffer and full queue.

Applied to 5.0/scsi-fixes. Thank you!

Patch

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 9cd404a..ac76201 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -148,7 +148,7 @@  struct tcmu_dev {
 	size_t ring_size;
 
 	struct mutex cmdr_lock;
-	struct list_head cmdr_queue;
+	struct list_head qfull_queue;
 
 	uint32_t dbi_max;
 	uint32_t dbi_thresh;
@@ -159,6 +159,7 @@  struct tcmu_dev {
 
 	struct timer_list cmd_timer;
 	unsigned int cmd_time_out;
+	struct list_head inflight_queue;
 
 	struct timer_list qfull_timer;
 	int qfull_time_out;
@@ -179,7 +180,7 @@  struct tcmu_dev {
 struct tcmu_cmd {
 	struct se_cmd *se_cmd;
 	struct tcmu_dev *tcmu_dev;
-	struct list_head cmdr_queue_entry;
+	struct list_head queue_entry;
 
 	uint16_t cmd_id;
 
@@ -192,6 +193,7 @@  struct tcmu_cmd {
 	unsigned long deadline;
 
 #define TCMU_CMD_BIT_EXPIRED 0
+#define TCMU_CMD_BIT_INFLIGHT 1
 	unsigned long flags;
 };
 /*
@@ -586,7 +588,7 @@  static struct tcmu_cmd *tcmu_alloc_cmd(struct se_cmd *se_cmd)
 	if (!tcmu_cmd)
 		return NULL;
 
-	INIT_LIST_HEAD(&tcmu_cmd->cmdr_queue_entry);
+	INIT_LIST_HEAD(&tcmu_cmd->queue_entry);
 	tcmu_cmd->se_cmd = se_cmd;
 	tcmu_cmd->tcmu_dev = udev;
 
@@ -915,11 +917,13 @@  static int tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd, unsigned int tmo,
 		return 0;
 
 	tcmu_cmd->deadline = round_jiffies_up(jiffies + msecs_to_jiffies(tmo));
-	mod_timer(timer, tcmu_cmd->deadline);
+	if (!timer_pending(timer))
+		mod_timer(timer, tcmu_cmd->deadline);
+
 	return 0;
 }
 
-static int add_to_cmdr_queue(struct tcmu_cmd *tcmu_cmd)
+static int add_to_qfull_queue(struct tcmu_cmd *tcmu_cmd)
 {
 	struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
 	unsigned int tmo;
@@ -942,7 +946,7 @@  static int add_to_cmdr_queue(struct tcmu_cmd *tcmu_cmd)
 	if (ret)
 		return ret;
 
-	list_add_tail(&tcmu_cmd->cmdr_queue_entry, &udev->cmdr_queue);
+	list_add_tail(&tcmu_cmd->queue_entry, &udev->qfull_queue);
 	pr_debug("adding cmd %u on dev %s to ring space wait queue\n",
 		 tcmu_cmd->cmd_id, udev->name);
 	return 0;
@@ -999,7 +1003,7 @@  static sense_reason_t queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, int *scsi_err)
 	base_command_size = tcmu_cmd_get_base_cmd_size(tcmu_cmd->dbi_cnt);
 	command_size = tcmu_cmd_get_cmd_size(tcmu_cmd, base_command_size);
 
-	if (!list_empty(&udev->cmdr_queue))
+	if (!list_empty(&udev->qfull_queue))
 		goto queue;
 
 	mb = udev->mb_addr;
@@ -1096,13 +1100,16 @@  static sense_reason_t queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, int *scsi_err)
 	UPDATE_HEAD(mb->cmd_head, command_size, udev->cmdr_size);
 	tcmu_flush_dcache_range(mb, sizeof(*mb));
 
+	list_add_tail(&tcmu_cmd->queue_entry, &udev->inflight_queue);
+	set_bit(TCMU_CMD_BIT_INFLIGHT, &tcmu_cmd->flags);
+
 	/* TODO: only if FLUSH and FUA? */
 	uio_event_notify(&udev->uio_info);
 
 	return 0;
 
 queue:
-	if (add_to_cmdr_queue(tcmu_cmd)) {
+	if (add_to_qfull_queue(tcmu_cmd)) {
 		*scsi_err = TCM_OUT_OF_RESOURCES;
 		return -1;
 	}
@@ -1145,6 +1152,8 @@  static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *
 	if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags))
 		goto out;
 
+	list_del_init(&cmd->queue_entry);
+
 	tcmu_cmd_reset_dbi_cur(cmd);
 
 	if (entry->hdr.uflags & TCMU_UFLAG_UNKNOWN_OP) {
@@ -1194,9 +1203,29 @@  static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *
 	tcmu_free_cmd(cmd);
 }
 
+static void tcmu_set_next_deadline(struct list_head *queue,
+				   struct timer_list *timer)
+{
+	struct tcmu_cmd *tcmu_cmd, *tmp_cmd;
+	unsigned long deadline = 0;
+
+	list_for_each_entry_safe(tcmu_cmd, tmp_cmd, queue, queue_entry) {
+		if (!time_after(jiffies, tcmu_cmd->deadline)) {
+			deadline = tcmu_cmd->deadline;
+			break;
+		}
+	}
+
+	if (deadline)
+		mod_timer(timer, deadline);
+	else
+		del_timer(timer);
+}
+
 static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 {
 	struct tcmu_mailbox *mb;
+	struct tcmu_cmd *cmd;
 	int handled = 0;
 
 	if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags)) {
@@ -1210,7 +1239,6 @@  static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 	while (udev->cmdr_last_cleaned != READ_ONCE(mb->cmd_tail)) {
 
 		struct tcmu_cmd_entry *entry = (void *) mb + CMDR_OFF + udev->cmdr_last_cleaned;
-		struct tcmu_cmd *cmd;
 
 		tcmu_flush_dcache_range(entry, sizeof(*entry));
 
@@ -1243,7 +1271,7 @@  static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 		/* no more pending commands */
 		del_timer(&udev->cmd_timer);
 
-		if (list_empty(&udev->cmdr_queue)) {
+		if (list_empty(&udev->qfull_queue)) {
 			/*
 			 * no more pending or waiting commands so try to
 			 * reclaim blocks if needed.
@@ -1252,6 +1280,8 @@  static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 			    tcmu_global_max_blocks)
 				schedule_delayed_work(&tcmu_unmap_work, 0);
 		}
+	} else if (udev->cmd_time_out) {
+		tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);
 	}
 
 	return handled;
@@ -1271,7 +1301,7 @@  static int tcmu_check_expired_cmd(int id, void *p, void *data)
 	if (!time_after(jiffies, cmd->deadline))
 		return 0;
 
-	is_running = list_empty(&cmd->cmdr_queue_entry);
+	is_running = test_bit(TCMU_CMD_BIT_INFLIGHT, &cmd->flags);
 	se_cmd = cmd->se_cmd;
 
 	if (is_running) {
@@ -1288,12 +1318,11 @@  static int tcmu_check_expired_cmd(int id, void *p, void *data)
 		 */
 		scsi_status = SAM_STAT_CHECK_CONDITION;
 	} else {
-		list_del_init(&cmd->cmdr_queue_entry);
-
 		idr_remove(&udev->commands, id);
 		tcmu_free_cmd(cmd);
 		scsi_status = SAM_STAT_TASK_SET_FULL;
 	}
+	list_del_init(&cmd->queue_entry);
 
 	pr_debug("Timing out cmd %u on dev %s that is %s.\n",
 		 id, udev->name, is_running ? "inflight" : "queued");
@@ -1372,7 +1401,8 @@  static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 
 	INIT_LIST_HEAD(&udev->node);
 	INIT_LIST_HEAD(&udev->timedout_entry);
-	INIT_LIST_HEAD(&udev->cmdr_queue);
+	INIT_LIST_HEAD(&udev->qfull_queue);
+	INIT_LIST_HEAD(&udev->inflight_queue);
 	idr_init(&udev->commands);
 
 	timer_setup(&udev->qfull_timer, tcmu_qfull_timedout, 0);
@@ -1383,7 +1413,7 @@  static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 	return &udev->se_dev;
 }
 
-static bool run_cmdr_queue(struct tcmu_dev *udev, bool fail)
+static bool run_qfull_queue(struct tcmu_dev *udev, bool fail)
 {
 	struct tcmu_cmd *tcmu_cmd, *tmp_cmd;
 	LIST_HEAD(cmds);
@@ -1391,15 +1421,15 @@  static bool run_cmdr_queue(struct tcmu_dev *udev, bool fail)
 	sense_reason_t scsi_ret;
 	int ret;
 
-	if (list_empty(&udev->cmdr_queue))
+	if (list_empty(&udev->qfull_queue))
 		return true;
 
 	pr_debug("running %s's cmdr queue forcefail %d\n", udev->name, fail);
 
-	list_splice_init(&udev->cmdr_queue, &cmds);
+	list_splice_init(&udev->qfull_queue, &cmds);
 
-	list_for_each_entry_safe(tcmu_cmd, tmp_cmd, &cmds, cmdr_queue_entry) {
-		list_del_init(&tcmu_cmd->cmdr_queue_entry);
+	list_for_each_entry_safe(tcmu_cmd, tmp_cmd, &cmds, queue_entry) {
+		list_del_init(&tcmu_cmd->queue_entry);
 
 	        pr_debug("removing cmd %u on dev %s from queue\n",
 		         tcmu_cmd->cmd_id, udev->name);
@@ -1437,14 +1467,13 @@  static bool run_cmdr_queue(struct tcmu_dev *udev, bool fail)
 			 * cmd was requeued, so just put all cmds back in
 			 * the queue
 			 */
-			list_splice_tail(&cmds, &udev->cmdr_queue);
+			list_splice_tail(&cmds, &udev->qfull_queue);
 			drained = false;
-			goto done;
+			break;
 		}
 	}
-	if (list_empty(&udev->cmdr_queue))
-		del_timer(&udev->qfull_timer);
-done:
+
+	tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);
 	return drained;
 }
 
@@ -1454,7 +1483,7 @@  static int tcmu_irqcontrol(struct uio_info *info, s32 irq_on)
 
 	mutex_lock(&udev->cmdr_lock);
 	tcmu_handle_completions(udev);
-	run_cmdr_queue(udev, false);
+	run_qfull_queue(udev, false);
 	mutex_unlock(&udev->cmdr_lock);
 
 	return 0;
@@ -1982,7 +2011,7 @@  static void tcmu_block_dev(struct tcmu_dev *udev)
 	/* complete IO that has executed successfully */
 	tcmu_handle_completions(udev);
 	/* fail IO waiting to be queued */
-	run_cmdr_queue(udev, true);
+	run_qfull_queue(udev, true);
 
 unlock:
 	mutex_unlock(&udev->cmdr_lock);
@@ -1997,7 +2026,7 @@  static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)
 	mutex_lock(&udev->cmdr_lock);
 
 	idr_for_each_entry(&udev->commands, cmd, i) {
-		if (!list_empty(&cmd->cmdr_queue_entry))
+		if (!test_bit(TCMU_CMD_BIT_INFLIGHT, &cmd->flags))
 			continue;
 
 		pr_debug("removing cmd %u on dev %s from ring (is expired %d)\n",
@@ -2006,6 +2035,7 @@  static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)
 
 		idr_remove(&udev->commands, i);
 		if (!test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
+			list_del_init(&cmd->queue_entry);
 			if (err_level == 1) {
 				/*
 				 * Userspace was not able to start the
@@ -2666,6 +2696,10 @@  static void check_timedout_devices(void)
 
 		mutex_lock(&udev->cmdr_lock);
 		idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);
+
+		tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);
+		tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);
+
 		mutex_unlock(&udev->cmdr_lock);
 
 		spin_lock_bh(&timed_out_udevs_lock);