target: Fix Task Aborted Status (TAS) handling

This patch addresses three of long standing issues wrt to Task
Aborted Status (TAS) handling.

The first is the incorrect assumption in core_tmr_handle_tas_abort()
that TASK_ABORTED status is sent for the task referenced by TMR
ABORT_TASK, and sending TASK_ABORTED status for TMR LUN_RESET on
the same nexus the LUN_RESET was received.

The second is to ensure the lun reference count is dropped within
transport_cmd_finish_abort() by calling transport_lun_remove_cmd()
before invoking transport_cmd_check_stop_to_fabric().

The last is to fix the delayed TAS handling to allow outstanding
WRITEs to complete before sending the TASK_ABORTED status. This
includes changing transport_check_aborted_status() to avoid
processing when SCF_SEND_DELAYED_TAS has not be set, and updating
transport_send_task_abort() to drop the SCF_SENT_DELAYED_TAS
check.

Signed-off-by: Alex Leung <amleung21@yahoo.com>
Cc: Alex Leung <amleung21@yahoo.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_tmr.c

@@ -87,14 +87,17 @@ static void core_tmr_handle_tas_abort(
 	struct se_cmd *cmd,
 	int tas)
 {
+	bool remove = true;
 	/*
 	 * TASK ABORTED status (TAS) bit support
 	*/
 	if ((tmr_nacl &&
-	     (tmr_nacl == cmd->se_sess->se_node_acl)) || tas)
+	     (tmr_nacl != cmd->se_sess->se_node_acl)) && tas) {
+		remove = false;
 		transport_send_task_abort(cmd);
+	}
 
-	transport_cmd_finish_abort(cmd, 0);
+	transport_cmd_finish_abort(cmd, remove);
 }
 
 static int target_check_cdb_and_preempt(struct list_head *list,
@@ -150,18 +153,9 @@ void core_tmr_abort_task(
 
 		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);
+		transport_cmd_finish_abort(se_cmd, true);
 
 		printk("ABORT_TASK: Sending TMR_FUNCTION_COMPLETE for"
 				" ref_tag: %d\n", ref_tag);

drivers/target/target_core_transport.c

@@ -603,6 +603,9 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd)
 
 void transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
 {
+	if (cmd->se_cmd_flags & SCF_SE_LUN_CMD)
+		transport_lun_remove_cmd(cmd);
+
 	if (transport_cmd_check_stop_to_fabric(cmd))
 		return;
 	if (remove)
@@ -2784,13 +2787,17 @@ int transport_check_aborted_status(struct se_cmd *cmd, int send_status)
 	if (!(cmd->transport_state & CMD_T_ABORTED))
 		return 0;
 
-	if (!send_status || (cmd->se_cmd_flags & SCF_SENT_DELAYED_TAS))
+	/*
+	 * If cmd has been aborted but either no status is to be sent or it has
+	 * already been sent, just return
+	 */
+	if (!send_status || !(cmd->se_cmd_flags & SCF_SEND_DELAYED_TAS))
 		return 1;
 
 	pr_debug("Sending delayed SAM_STAT_TASK_ABORTED status for CDB: 0x%02x ITT: 0x%08x\n",
 		 cmd->t_task_cdb[0], cmd->se_tfo->get_task_tag(cmd));
 
-	cmd->se_cmd_flags |= SCF_SENT_DELAYED_TAS;
+	cmd->se_cmd_flags &= ~SCF_SEND_DELAYED_TAS;
 	cmd->scsi_status = SAM_STAT_TASK_ABORTED;
 	trace_target_cmd_complete(cmd);
 	cmd->se_tfo->queue_status(cmd);
@@ -2804,7 +2811,7 @@ void transport_send_task_abort(struct se_cmd *cmd)
 	unsigned long flags;
 
 	spin_lock_irqsave(&cmd->t_state_lock, flags);
-	if (cmd->se_cmd_flags & (SCF_SENT_CHECK_CONDITION | SCF_SENT_DELAYED_TAS)) {
+	if (cmd->se_cmd_flags & (SCF_SENT_CHECK_CONDITION)) {
 		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 		return;
 	}
@@ -2819,6 +2826,7 @@ void transport_send_task_abort(struct se_cmd *cmd)
 	if (cmd->data_direction == DMA_TO_DEVICE) {
 		if (cmd->se_tfo->write_pending_status(cmd) != 0) {
 			cmd->transport_state |= CMD_T_ABORTED;
+			cmd->se_cmd_flags |= SCF_SEND_DELAYED_TAS;
 			smp_mb__after_atomic_inc();
 			return;
 		}

include/target/target_core_base.h

@@ -162,7 +162,7 @@ enum se_cmd_flags_table {
 	SCF_SENT_CHECK_CONDITION	= 0x00000800,
 	SCF_OVERFLOW_BIT		= 0x00001000,
 	SCF_UNDERFLOW_BIT		= 0x00002000,
-	SCF_SENT_DELAYED_TAS		= 0x00004000,
+	SCF_SEND_DELAYED_TAS		= 0x00004000,
 	SCF_ALUA_NON_OPTIMIZED		= 0x00008000,
 	SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC = 0x00020000,
 	SCF_ACK_KREF			= 0x00040000,