target: simplify command to task linkage

Now that we only have a single task per command we can use a direct pointer
to it instead of list.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 44 insertions, 83 deletions

diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index f015839aef89..98204d06cdf6 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -321,13 +321,11 @@ static void core_tmr_drain_task_list(
                         cmd->se_tfo->get_cmd_state(cmd), cmd->t_state,
                         cmd->t_task_cdb[0]);
                 pr_debug("LUN_RESET: ITT[0x%08x] - pr_res_key: 0x%016Lx"
-                        " t_task_cdbs: %d t_task_cdbs_left: %d"
-                        " t_task_cdbs_sent: %d -- CMD_T_ACTIVE: %d"
+                        " t_task_cdbs_left: %d"
+                        " -- CMD_T_ACTIVE: %d"
                         " CMD_T_STOP: %d CMD_T_SENT: %d\n",
                         cmd->se_tfo->get_task_tag(cmd), cmd->pr_res_key,
-                        cmd->t_task_list_num,
                         atomic_read(&cmd->t_task_cdbs_left),
-                        atomic_read(&cmd->t_task_cdbs_sent),
                         (cmd->transport_state & CMD_T_ACTIVE) != 0,
                         (cmd->transport_state & CMD_T_STOP) != 0,
                         (cmd->transport_state & CMD_T_SENT) != 0);
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 5267198688fe..a2246359e6f4 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -453,9 +453,10 @@ static void transport_all_task_dev_remove_state(struct se_cmd *cmd)
         if (!dev)
                 return;
 
-        list_for_each_entry(task, &cmd->t_task_list, t_list) {
+        task = cmd->t_task;
+        if (task) {
                 if (task->task_flags & TF_ACTIVE)
-                        continue;
+                        return;
 
                 spin_lock_irqsave(&dev->execute_task_lock, flags);
                 if (task->t_state_active) {
@@ -675,8 +676,7 @@ static void transport_remove_cmd_from_queue(struct se_cmd *cmd)
  */
 void transport_complete_sync_cache(struct se_cmd *cmd, int good)
 {
-        struct se_task *task = list_entry(cmd->t_task_list.next,
-                                struct se_task, t_list);
+        struct se_task *task = cmd->t_task;
 
         if (good) {
                 cmd->scsi_status = SAM_STAT_GOOD;
@@ -774,8 +774,7 @@ EXPORT_SYMBOL(transport_complete_task);
 
 void target_complete_cmd(struct se_cmd *cmd, u8 scsi_status)
 {
-        struct se_task *task = list_entry(cmd->t_task_list.next,
-                                struct se_task, t_list);
+        struct se_task *task = cmd->t_task;
 
         task->task_scsi_status = scsi_status;
         transport_complete_task(task, scsi_status == GOOD);
@@ -791,7 +790,6 @@ EXPORT_SYMBOL(target_complete_cmd);
  */
 static inline int transport_add_task_check_sam_attr(
         struct se_task *task,
-        struct se_task *task_prev,
         struct se_device *dev)
 {
         /*
@@ -805,14 +803,10 @@ static inline int transport_add_task_check_sam_attr(
         /*
          * HEAD_OF_QUEUE attribute for received CDB, which means
          * the first task that is associated with a struct se_cmd goes to
-         * head of the struct se_device->execute_task_list, and task_prev
-         * after that for each subsequent task
+         * head of the struct se_device->execute_task_list.
          */
         if (task->task_se_cmd->sam_task_attr == MSG_HEAD_TAG) {
-                list_add(&task->t_execute_list,
-                                (task_prev != NULL) ?
-                                &task_prev->t_execute_list :
-                                &dev->execute_task_list);
+                list_add(&task->t_execute_list, &dev->execute_task_list);
 
                 pr_debug("Set HEAD_OF_QUEUE for task CDB: 0x%02x"
                                 " in execution queue\n",
@@ -834,12 +828,11 @@ static inline int transport_add_task_check_sam_attr(
  */
 static void __transport_add_task_to_execute_queue(
         struct se_task *task,
-        struct se_task *task_prev,
         struct se_device *dev)
 {
         int head_of_queue;
 
-        head_of_queue = transport_add_task_check_sam_attr(task, task_prev, dev);
+        head_of_queue = transport_add_task_check_sam_attr(task, dev);
         atomic_inc(&dev->execute_tasks);
 
         if (task->t_state_active)
@@ -850,9 +843,7 @@ static void __transport_add_task_to_execute_queue(
          * will always return head_of_queue == 0 here
          */
         if (head_of_queue)
-                list_add(&task->t_state_list, (task_prev) ?
-                                &task_prev->t_state_list :
-                                &dev->state_task_list);
+                list_add(&task->t_state_list, &dev->state_task_list);
         else
                 list_add_tail(&task->t_state_list, &dev->state_task_list);
 
@@ -870,7 +861,11 @@ static void transport_add_tasks_to_state_queue(struct se_cmd *cmd)
         unsigned long flags;
 
         spin_lock_irqsave(&cmd->t_state_lock, flags);
-        list_for_each_entry(task, &cmd->t_task_list, t_list) {
+        task = cmd->t_task;
+        if (task) {
+                if (task->task_flags & TF_ACTIVE)
+                        goto out;
+
                 spin_lock(&dev->execute_task_lock);
                 if (!task->t_state_active) {
                         list_add_tail(&task->t_state_list,
@@ -883,24 +878,17 @@ static void transport_add_tasks_to_state_queue(struct se_cmd *cmd)
                 }
                 spin_unlock(&dev->execute_task_lock);
         }
+out:
         spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 }
 
 static void __transport_add_tasks_from_cmd(struct se_cmd *cmd)
 {
-        struct se_device *dev = cmd->se_dev;
-        struct se_task *task, *task_prev = NULL;
+        struct se_task *task;
 
-        list_for_each_entry(task, &cmd->t_task_list, t_list) {
-                if (!list_empty(&task->t_execute_list))
-                        continue;
-                /*
-                 * __transport_add_task_to_execute_queue() handles the
-                 * SAM Task Attribute emulation if enabled
-                 */
-                __transport_add_task_to_execute_queue(task, task_prev, dev);
-                task_prev = task;
-        }
+        task = cmd->t_task;
+        if (task && list_empty(&task->t_execute_list))
+                __transport_add_task_to_execute_queue(task, cmd->se_dev);
 }
 
 static void transport_add_tasks_from_cmd(struct se_cmd *cmd)
@@ -1494,7 +1482,6 @@ void transport_init_se_cmd(
         INIT_LIST_HEAD(&cmd->se_qf_node);
         INIT_LIST_HEAD(&cmd->se_queue_node);
         INIT_LIST_HEAD(&cmd->se_cmd_list);
-        INIT_LIST_HEAD(&cmd->t_task_list);
         init_completion(&cmd->transport_lun_fe_stop_comp);
         init_completion(&cmd->transport_lun_stop_comp);
         init_completion(&cmd->t_transport_stop_comp);
@@ -1895,7 +1882,7 @@ bool target_stop_task(struct se_task *task, unsigned long *flags)
 
 static int transport_stop_tasks_for_cmd(struct se_cmd *cmd)
 {
-        struct se_task *task, *task_tmp;
+        struct se_task *task;
         unsigned long flags;
         int ret = 0;
 
@@ -1906,8 +1893,8 @@ static int transport_stop_tasks_for_cmd(struct se_cmd *cmd)
          * No tasks remain in the execution queue
          */
         spin_lock_irqsave(&cmd->t_state_lock, flags);
-        list_for_each_entry_safe(task, task_tmp,
-                                &cmd->t_task_list, t_list) {
+        task = cmd->t_task;
+        if (task) {
                 pr_debug("Processing task %p\n", task);
                 /*
                  * If the struct se_task has not been sent and is not active,
@@ -1921,7 +1908,7 @@ static int transport_stop_tasks_for_cmd(struct se_cmd *cmd)
 
                         pr_debug("Task %p removed from execute queue\n", task);
                         spin_lock_irqsave(&cmd->t_state_lock, flags);
-                        continue;
+                        goto out;
                 }
 
                 if (!target_stop_task(task, &flags)) {
@@ -1929,8 +1916,8 @@ static int transport_stop_tasks_for_cmd(struct se_cmd *cmd)
                         ret++;
                 }
         }
+out:
         spin_unlock_irqrestore(&cmd->t_state_lock, flags);
-
         return ret;
 }
 
@@ -1947,12 +1934,10 @@ void transport_generic_request_failure(struct se_cmd *cmd)
         pr_debug("-----[ i_state: %d t_state: %d scsi_sense_reason: %d\n",
                 cmd->se_tfo->get_cmd_state(cmd),
                 cmd->t_state, cmd->scsi_sense_reason);
-        pr_debug("-----[ t_tasks: %d t_task_cdbs_left: %d"
-                " t_task_cdbs_sent: %d t_task_cdbs_ex_left: %d --"
+        pr_debug("-----[ t_task_cdbs_left: %d"
+                " t_task_cdbs_ex_left: %d --"
                 " CMD_T_ACTIVE: %d CMD_T_STOP: %d CMD_T_SENT: %d\n",
-                cmd->t_task_list_num,
                 atomic_read(&cmd->t_task_cdbs_left),
-                atomic_read(&cmd->t_task_cdbs_sent),
                 atomic_read(&cmd->t_task_cdbs_ex_left),
                 (cmd->transport_state & CMD_T_ACTIVE) != 0,
                 (cmd->transport_state & CMD_T_STOP) != 0,
@@ -2212,11 +2197,7 @@ check_depth:
         cmd = task->task_se_cmd;
         spin_lock_irqsave(&cmd->t_state_lock, flags);
         task->task_flags |= (TF_ACTIVE | TF_SENT);
-        atomic_inc(&cmd->t_task_cdbs_sent);
-
-        if (atomic_read(&cmd->t_task_cdbs_sent) ==
-            cmd->t_task_list_num)
-                cmd->transport_state |= CMD_T_SENT;
+        cmd->transport_state |= CMD_T_SENT;
 
         spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 
@@ -2458,7 +2439,7 @@ static int transport_get_sense_data(struct se_cmd *cmd)
 {
         unsigned char *buffer = cmd->sense_buffer, *sense_buffer = NULL;
         struct se_device *dev = cmd->se_dev;
-        struct se_task *task = NULL, *task_tmp;
+        struct se_task *task = NULL;
         unsigned long flags;
         u32 offset = 0;
 
@@ -2473,15 +2454,15 @@ static int transport_get_sense_data(struct se_cmd *cmd)
                 return 0;
         }
 
-        list_for_each_entry_safe(task, task_tmp,
-                                &cmd->t_task_list, t_list) {
+        task = cmd->t_task;
+        if (task) {
                 if (!(task->task_flags & TF_HAS_SENSE))
-                        continue;
+                        goto out;
 
                 if (!dev->transport->get_sense_buffer) {
                         pr_err("dev->transport->get_sense_buffer"
                                         " is NULL\n");
-                        continue;
+                        goto out;
                 }
 
                 sense_buffer = dev->transport->get_sense_buffer(task);
@@ -2489,7 +2470,7 @@ static int transport_get_sense_data(struct se_cmd *cmd)
                         pr_err("ITT[0x%08x]_TASK[%p]: Unable to locate"
                                 " sense buffer for task with sense\n",
                                 cmd->se_tfo->get_task_tag(cmd), task);
-                        continue;
+                        goto out;
                 }
                 spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 
@@ -2509,8 +2490,8 @@ static int transport_get_sense_data(struct se_cmd *cmd)
                                 cmd->scsi_status);
                 return 0;
         }
+out:
         spin_unlock_irqrestore(&cmd->t_state_lock, flags);
-
         return -1;
 }
 
@@ -3429,24 +3410,11 @@ queue_full:
 
 static void transport_free_dev_tasks(struct se_cmd *cmd)
 {
-        struct se_task *task, *task_tmp;
-        unsigned long flags;
-        LIST_HEAD(dispose_list);
-
-        spin_lock_irqsave(&cmd->t_state_lock, flags);
-        list_for_each_entry_safe(task, task_tmp,
-                                &cmd->t_task_list, t_list) {
-                if (!(task->task_flags & TF_ACTIVE))
-                        list_move_tail(&task->t_list, &dispose_list);
-        }
-        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
-
-        while (!list_empty(&dispose_list)) {
-                task = list_first_entry(&dispose_list, struct se_task, t_list);
+        struct se_task *task;
 
-                list_del(&task->t_list);
+        task = cmd->t_task;
+        if (task && !(task->task_flags & TF_ACTIVE))
                 cmd->se_dev->transport->free_task(task);
-        }
 }
 
 static inline void transport_free_sgl(struct scatterlist *sgl, int nents)
@@ -3690,7 +3658,6 @@ int transport_generic_new_cmd(struct se_cmd *cmd)
 {
         struct se_device *dev = cmd->se_dev;
         struct se_task *task;
-        unsigned long flags;
         int ret = 0;
 
         /*
@@ -3742,7 +3709,6 @@ int transport_generic_new_cmd(struct se_cmd *cmd)
                 goto out_fail;
         }
 
-        INIT_LIST_HEAD(&task->t_list);
         INIT_LIST_HEAD(&task->t_execute_list);
         INIT_LIST_HEAD(&task->t_state_list);
         init_completion(&task->task_stop_comp);
@@ -3751,16 +3717,13 @@ int transport_generic_new_cmd(struct se_cmd *cmd)
         task->task_sg = cmd->t_data_sg;
         task->task_sg_nents = cmd->t_data_nents;
 
-        spin_lock_irqsave(&cmd->t_state_lock, flags);
-        list_add_tail(&task->t_list, &cmd->t_task_list);
-        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+        cmd->t_task = task;
 
         atomic_inc(&cmd->t_fe_count);
         atomic_inc(&cmd->t_se_count);
 
-        cmd->t_task_list_num = 1;
-        atomic_set(&cmd->t_task_cdbs_left, cmd->t_task_list_num);
-        atomic_set(&cmd->t_task_cdbs_ex_left, cmd->t_task_list_num);
+        atomic_set(&cmd->t_task_cdbs_left, 1);
+        atomic_set(&cmd->t_task_cdbs_ex_left, 1);
 
         /*
          * For WRITEs, let the fabric know its buffer is ready..
@@ -4026,8 +3989,8 @@ static int transport_lun_wait_for_tasks(struct se_cmd *cmd, struct se_lun *lun)
 
         ret = transport_stop_tasks_for_cmd(cmd);
 
-        pr_debug("ConfigFS: cmd: %p t_tasks: %d stop tasks ret:"
-                        " %d\n", cmd, cmd->t_task_list_num, ret);
+        pr_debug("ConfigFS: cmd: %p stop tasks ret:"
+                        " %d\n", cmd, ret);
         if (!ret) {
                 pr_debug("ConfigFS: ITT[0x%08x] - stopping cmd....\n",
                                 cmd->se_tfo->get_task_tag(cmd));