target: Add TMR_ABORT_TASK task management support

This patch adds initial support for TMR_ABORT_TASK ops for se_cmd
descriptors using se_sess->sess_cmd_list and se_cmd->cmd_kref counting.

It will perform an explict abort for all outstanding se_cmd ops based
upon tmr->ref_task_tag that have not been set CMD_T_COMPLETE.
It will cancel se_cmd->work and wait for backing I/O to complete before
attempting to send SAM_STAT_TASK_ABORTED and perform
target_put_sess_cmd() to release the referenced descriptor.

It also adds a CMD_T_ABORTED check into transport_complete_task() to
catch the completion from backend I/O that has been aborted, and
updates transport_wait_for_tasks() to allow CMD_T_ABORTED usage with
core_tmr_abort_task() context.
Reported-by: Roland Dreier <roland@purestorage.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_internal.h

@@ -75,6 +75,8 @@ struct se_hba *core_alloc_hba(const char *, u32, u32);
 int	core_delete_hba(struct se_hba *);
 
 /* target_core_tmr.c */
+void	core_tmr_abort_task(struct se_device *, struct se_tmr_req *,
+			struct se_session *);
 int	core_tmr_lun_reset(struct se_device *, struct se_tmr_req *,
 		struct list_head *, struct se_cmd *);
 

drivers/target/target_core_tmr.c

@@ -118,6 +118,70 @@ static int target_check_cdb_and_preempt(struct list_head *list,
 	return 1;
 }
 
+void core_tmr_abort_task(
+	struct se_device *dev,
+	struct se_tmr_req *tmr,
+	struct se_session *se_sess)
+{
+	struct se_cmd *se_cmd, *tmp_cmd;
+	unsigned long flags;
+	int ref_tag;
+
+	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
+	list_for_each_entry_safe(se_cmd, tmp_cmd,
+			&se_sess->sess_cmd_list, se_cmd_list) {
+
+		if (dev != se_cmd->se_dev)
+			continue;
+		ref_tag = se_cmd->se_tfo->get_task_tag(se_cmd);
+		if (tmr->ref_task_tag != ref_tag)
+			continue;
+
+		printk("ABORT_TASK: Found referenced %s task_tag: %u\n",
+			se_cmd->se_tfo->get_fabric_name(), ref_tag);
+
+		spin_lock_irq(&se_cmd->t_state_lock);
+		if (se_cmd->transport_state & CMD_T_COMPLETE) {
+			printk("ABORT_TASK: ref_tag: %u already complete, skipping\n", ref_tag);
+			spin_unlock_irq(&se_cmd->t_state_lock);
+			spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+			goto out;
+		}
+		se_cmd->transport_state |= CMD_T_ABORTED;
+		spin_unlock_irq(&se_cmd->t_state_lock);
+
+		list_del_init(&se_cmd->se_cmd_list);
+		kref_get(&se_cmd->cmd_kref);
+		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+
+		cancel_work_sync(&se_cmd->work);
+		transport_wait_for_tasks(se_cmd);
+		/*
+		 * Now send SAM_STAT_TASK_ABORTED status for the referenced
+		 * se_cmd descriptor..
+		 */
+		transport_send_task_abort(se_cmd);
+		/*
+		 * Also deal with possible extra acknowledge reference..
+		 */
+		if (se_cmd->se_cmd_flags & SCF_ACK_KREF)
+			target_put_sess_cmd(se_sess, se_cmd);
+
+		target_put_sess_cmd(se_sess, se_cmd);
+
+		printk("ABORT_TASK: Sending TMR_FUNCTION_COMPLETE for"
+				" ref_tag: %d\n", ref_tag);
+		tmr->response = TMR_FUNCTION_COMPLETE;
+		return;
+	}
+	spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+
+out:
+	printk("ABORT_TASK: Sending TMR_TASK_DOES_NOT_EXIST for ref_tag: %d\n",
+			tmr->ref_task_tag);
+	tmr->response = TMR_TASK_DOES_NOT_EXIST;
+}
+
 static void core_tmr_drain_tmr_list(
 	struct se_device *dev,
 	struct se_tmr_req *tmr,

drivers/target/target_core_transport.c

@@ -699,17 +699,24 @@ void transport_complete_task(struct se_task *task, int success)
 		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 		return;
 	}
-
-	if (cmd->transport_state & CMD_T_FAILED) {
+	/*
+	 * Check for case where an explict ABORT_TASK has been received
+	 * and transport_wait_for_tasks() will be waiting for completion..
+	 */
+	if (cmd->transport_state & CMD_T_ABORTED &&
+	    cmd->transport_state & CMD_T_STOP) {
+		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+		complete(&cmd->t_transport_stop_comp);
+		return;
+	} else if (cmd->transport_state & CMD_T_FAILED) {
 		cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 		INIT_WORK(&cmd->work, target_complete_failure_work);
 	} else {
-		cmd->transport_state |= CMD_T_COMPLETE;
 		INIT_WORK(&cmd->work, target_complete_ok_work);
 	}
 
 	cmd->t_state = TRANSPORT_COMPLETE;
-	cmd->transport_state |= CMD_T_ACTIVE;
+	cmd->transport_state |= (CMD_T_COMPLETE | CMD_T_ACTIVE);
 	spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 
 	queue_work(target_completion_wq, &cmd->work);
@@ -4374,8 +4381,7 @@ bool transport_wait_for_tasks(struct se_cmd *cmd)
 		cmd->transport_state &= ~CMD_T_LUN_STOP;
 	}
 
-	if (!(cmd->transport_state & CMD_T_ACTIVE) ||
-	     (cmd->transport_state & CMD_T_ABORTED)) {
+	if (!(cmd->transport_state & CMD_T_ACTIVE)) {
 		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 		return false;
 	}
@@ -4681,7 +4687,7 @@ static int transport_generic_do_tmr(struct se_cmd *cmd)
 
 	switch (tmr->function) {
 	case TMR_ABORT_TASK:
-		tmr->response = TMR_FUNCTION_REJECTED;
+		core_tmr_abort_task(dev, tmr, cmd->se_sess);
 		break;
 	case TMR_ABORT_TASK_SET:
 	case TMR_CLEAR_ACA: