drivers/target/target_core_tmr.c - linux - Git at Google

 /*******************************************************************************
  * Filename:  target_core_tmr.c
  *
  * This file contains SPC-3 task management infrastructure
  *
  * (c) Copyright 2009-2013 Datera, Inc.
  *
  * Nicholas A. Bellinger <nab@kernel.org>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  *
  ******************************************************************************/

 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/list.h>
 #include <linux/export.h>

 #include <target/target_core_base.h>
 #include <target/target_core_backend.h>
 #include <target/target_core_fabric.h>

 #include "target_core_internal.h"
 #include "target_core_alua.h"
 #include "target_core_pr.h"

 int core_tmr_alloc_req(
 	struct se_cmd *se_cmd,
 	void *fabric_tmr_ptr,
 	u8 function,
 	gfp_t gfp_flags)
 {
 	struct se_tmr_req *tmr;

 	tmr = kzalloc(sizeof(struct se_tmr_req), gfp_flags);
 	if (!tmr) {
 		pr_err("Unable to allocate struct se_tmr_req\n");
 		return -ENOMEM;
 	}

 	se_cmd->se_cmd_flags |= SCF_SCSI_TMR_CDB;
 	se_cmd->se_tmr_req = tmr;
 	tmr->task_cmd = se_cmd;
 	tmr->fabric_tmr_ptr = fabric_tmr_ptr;
 	tmr->function = function;
 	INIT_LIST_HEAD(&tmr->tmr_list);

 	return 0;
 }
 EXPORT_SYMBOL(core_tmr_alloc_req);

 void core_tmr_release_req(struct se_tmr_req *tmr)
 {
 	struct se_device *dev = tmr->tmr_dev;
 	unsigned long flags;

 	if (dev) {
 		spin_lock_irqsave(&dev->se_tmr_lock, flags);
 		list_del_init(&tmr->tmr_list);
 		spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
 	}

 	kfree(tmr);
 }

 static int target_check_cdb_and_preempt(struct list_head *list,
 		struct se_cmd *cmd)
 {
 	struct t10_pr_registration *reg;

 	if (!list)
 		return 0;
 	list_for_each_entry(reg, list, pr_reg_abort_list) {
 		if (reg->pr_res_key == cmd->pr_res_key)
 			return 0;
 	}

 	return 1;
 }

 static bool __target_check_io_state(struct se_cmd *se_cmd,
 				    struct se_session *tmr_sess, int tas)
 {
 	struct se_session *sess = se_cmd->se_sess;

 	assert_spin_locked(&sess->sess_cmd_lock);
 	WARN_ON_ONCE(!irqs_disabled());
 	/*
 	 * If command already reached CMD_T_COMPLETE state within
 	 * target_complete_cmd() or CMD_T_FABRIC_STOP due to shutdown,
 	 * this se_cmd has been passed to fabric driver and will
 	 * not be aborted.
 	 *
 	 * Otherwise, obtain a local se_cmd->cmd_kref now for TMR
 	 * ABORT_TASK + LUN_RESET for CMD_T_ABORTED processing as
 	 * long as se_cmd->cmd_kref is still active unless zero.
 	 */
 	spin_lock(&se_cmd->t_state_lock);
 	if (se_cmd->transport_state & (CMD_T_COMPLETE | CMD_T_FABRIC_STOP)) {
 		pr_debug("Attempted to abort io tag: %llu already complete or"
 			" fabric stop, skipping\n", se_cmd->tag);
 		spin_unlock(&se_cmd->t_state_lock);
 		return false;
 	}
 	se_cmd->transport_state |= CMD_T_ABORTED;

 	if ((tmr_sess != se_cmd->se_sess) && tas)
 		se_cmd->transport_state |= CMD_T_TAS;

 	spin_unlock(&se_cmd->t_state_lock);

 	return kref_get_unless_zero(&se_cmd->cmd_kref);
 }

 void core_tmr_abort_task(
 	struct se_device *dev,
 	struct se_tmr_req *tmr,
 	struct se_session *se_sess)
 {
 	struct se_cmd *se_cmd;
 	unsigned long flags;
 	u64 ref_tag;

 	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
 	list_for_each_entry(se_cmd, &se_sess->sess_cmd_list, se_cmd_list) {

 		if (dev != se_cmd->se_dev)
 			continue;

 		/* skip task management functions, including tmr->task_cmd */
 		if (se_cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
 			continue;

 		ref_tag = se_cmd->tag;
 		if (tmr->ref_task_tag != ref_tag)
 			continue;

 		printk("ABORT_TASK: Found referenced %s task_tag: %llu\n",
 			se_cmd->se_tfo->fabric_name, ref_tag);

 		if (!__target_check_io_state(se_cmd, se_sess,
 					     dev->dev_attrib.emulate_tas))
 			continue;

 		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

 		/*
 		 * Ensure that this ABORT request is visible to the LU RESET
 		 * code.
 		 */
 		if (!tmr->tmr_dev)
 			WARN_ON_ONCE(transport_lookup_tmr_lun(tmr->task_cmd,
 						se_cmd->orig_fe_lun) < 0);

 		target_put_cmd_and_wait(se_cmd);

 		printk("ABORT_TASK: Sending TMR_FUNCTION_COMPLETE for"
 				" ref_tag: %llu\n", ref_tag);
 		tmr->response = TMR_FUNCTION_COMPLETE;
 		atomic_long_inc(&dev->aborts_complete);
 		return;
 	}
 	spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

 	printk("ABORT_TASK: Sending TMR_TASK_DOES_NOT_EXIST for ref_tag: %lld\n",
 			tmr->ref_task_tag);
 	tmr->response = TMR_TASK_DOES_NOT_EXIST;
 	atomic_long_inc(&dev->aborts_no_task);
 }

 static void core_tmr_drain_tmr_list(
 	struct se_device *dev,
 	struct se_tmr_req *tmr,
 	struct list_head *preempt_and_abort_list)
 {
 	LIST_HEAD(drain_tmr_list);
 	struct se_session *sess;
 	struct se_tmr_req *tmr_p, *tmr_pp;
 	struct se_cmd *cmd;
 	unsigned long flags;
 	bool rc;
 	/*
 	 * Release all pending and outgoing TMRs aside from the received
 	 * LUN_RESET tmr..
 	 */
 	spin_lock_irqsave(&dev->se_tmr_lock, flags);
 	if (tmr)
 		list_del_init(&tmr->tmr_list);
 	list_for_each_entry_safe(tmr_p, tmr_pp, &dev->dev_tmr_list, tmr_list) {
 		cmd = tmr_p->task_cmd;
 		if (!cmd) {
 			pr_err("Unable to locate struct se_cmd for TMR\n");
 			continue;
 		}
 		/*
 		 * If this function was called with a valid pr_res_key
 		 * parameter (eg: for PROUT PREEMPT_AND_ABORT service action
 		 * skip non registration key matching TMRs.
 		 */
 		if (target_check_cdb_and_preempt(preempt_and_abort_list, cmd))
 			continue;

 		sess = cmd->se_sess;
 		if (WARN_ON_ONCE(!sess))
 			continue;

 		spin_lock(&sess->sess_cmd_lock);
 		rc = __target_check_io_state(cmd, sess, 0);
 		spin_unlock(&sess->sess_cmd_lock);

 		if (!rc) {
 			printk("LUN_RESET TMR: non-zero kref_get_unless_zero\n");
 			continue;
 		}

 		list_move_tail(&tmr_p->tmr_list, &drain_tmr_list);
 	}
 	spin_unlock_irqrestore(&dev->se_tmr_lock, flags);

 	list_for_each_entry_safe(tmr_p, tmr_pp, &drain_tmr_list, tmr_list) {
 		list_del_init(&tmr_p->tmr_list);
 		cmd = tmr_p->task_cmd;

 		pr_debug("LUN_RESET: %s releasing TMR %p Function: 0x%02x,"
 			" Response: 0x%02x, t_state: %d\n",
 			(preempt_and_abort_list) ? "Preempt" : "", tmr_p,
 			tmr_p->function, tmr_p->response, cmd->t_state);

 		target_put_cmd_and_wait(cmd);
 	}
 }

 /**
  * core_tmr_drain_state_list() - abort SCSI commands associated with a device
  *
  * @dev:       Device for which to abort outstanding SCSI commands.
  * @prout_cmd: Pointer to the SCSI PREEMPT AND ABORT if this function is called
  *             to realize the PREEMPT AND ABORT functionality.
  * @tmr_sess:  Session through which the LUN RESET has been received.
  * @tas:       Task Aborted Status (TAS) bit from the SCSI control mode page.
  *             A quote from SPC-4, paragraph "7.5.10 Control mode page":
  *             "A task aborted status (TAS) bit set to zero specifies that
  *             aborted commands shall be terminated by the device server
  *             without any response to the application client. A TAS bit set
  *             to one specifies that commands aborted by the actions of an I_T
  *             nexus other than the I_T nexus on which the command was
  *             received shall be completed with TASK ABORTED status."
  * @preempt_and_abort_list: For the PREEMPT AND ABORT functionality, a list
  *             with registrations that will be preempted.
  */
 static void core_tmr_drain_state_list(
 	struct se_device *dev,
 	struct se_cmd *prout_cmd,
 	struct se_session *tmr_sess,
 	int tas,
 	struct list_head *preempt_and_abort_list)
 {
 	LIST_HEAD(drain_task_list);
 	struct se_session *sess;
 	struct se_cmd *cmd, *next;
 	unsigned long flags;
 	int rc;

 	/*
 	 * Complete outstanding commands with TASK_ABORTED SAM status.
 	 *
 	 * This is following sam4r17, section 5.6 Aborting commands, Table 38
 	 * for TMR LUN_RESET:
 	 *
 	 * a) "Yes" indicates that each command that is aborted on an I_T nexus
 	 * other than the one that caused the SCSI device condition is
 	 * completed with TASK ABORTED status, if the TAS bit is set to one in
 	 * the Control mode page (see SPC-4). "No" indicates that no status is
 	 * returned for aborted commands.
 	 *
 	 * d) If the logical unit reset is caused by a particular I_T nexus
 	 * (e.g., by a LOGICAL UNIT RESET task management function), then "yes"
 	 * (TASK_ABORTED status) applies.
 	 *
 	 * Otherwise (e.g., if triggered by a hard reset), "no"
 	 * (no TASK_ABORTED SAM status) applies.
 	 *
 	 * Note that this seems to be independent of TAS (Task Aborted Status)
 	 * in the Control Mode Page.
 	 */
 	spin_lock_irqsave(&dev->execute_task_lock, flags);
 	list_for_each_entry_safe(cmd, next, &dev->state_list, state_list) {
 		/*
 		 * For PREEMPT_AND_ABORT usage, only process commands
 		 * with a matching reservation key.
 		 */
 		if (target_check_cdb_and_preempt(preempt_and_abort_list, cmd))
 			continue;

 		/*
 		 * Not aborting PROUT PREEMPT_AND_ABORT CDB..
 		 */
 		if (prout_cmd == cmd)
 			continue;

 		sess = cmd->se_sess;
 		if (WARN_ON_ONCE(!sess))
 			continue;

 		spin_lock(&sess->sess_cmd_lock);
 		rc = __target_check_io_state(cmd, tmr_sess, tas);
 		spin_unlock(&sess->sess_cmd_lock);
 		if (!rc)
 			continue;

 		list_move_tail(&cmd->state_list, &drain_task_list);
 		cmd->state_active = false;
 	}
 	spin_unlock_irqrestore(&dev->execute_task_lock, flags);

 	while (!list_empty(&drain_task_list)) {
 		cmd = list_entry(drain_task_list.next, struct se_cmd, state_list);
 		list_del_init(&cmd->state_list);

 		target_show_cmd("LUN_RESET: ", cmd);
 		pr_debug("LUN_RESET: ITT[0x%08llx] - %s pr_res_key: 0x%016Lx\n",
 			 cmd->tag, (preempt_and_abort_list) ? "preempt" : "",
 			 cmd->pr_res_key);

 		target_put_cmd_and_wait(cmd);
 	}
 }

 int core_tmr_lun_reset(
         struct se_device *dev,
         struct se_tmr_req *tmr,
         struct list_head *preempt_and_abort_list,
         struct se_cmd *prout_cmd)
 {
 	struct se_node_acl *tmr_nacl = NULL;
 	struct se_portal_group *tmr_tpg = NULL;
 	struct se_session *tmr_sess = NULL;
 	int tas;
         /*
 	 * TASK_ABORTED status bit, this is configurable via ConfigFS
 	 * struct se_device attributes.  spc4r17 section 7.4.6 Control mode page
 	 *
 	 * A task aborted status (TAS) bit set to zero specifies that aborted
 	 * tasks shall be terminated by the device server without any response
 	 * to the application client. A TAS bit set to one specifies that tasks
 	 * aborted by the actions of an I_T nexus other than the I_T nexus on
 	 * which the command was received shall be completed with TASK ABORTED
 	 * status (see SAM-4).
 	 */
 	tas = dev->dev_attrib.emulate_tas;
 	/*
 	 * Determine if this se_tmr is coming from a $FABRIC_MOD
 	 * or struct se_device passthrough..
 	 */
 	if (tmr && tmr->task_cmd && tmr->task_cmd->se_sess) {
 		tmr_sess = tmr->task_cmd->se_sess;
 		tmr_nacl = tmr_sess->se_node_acl;
 		tmr_tpg = tmr_sess->se_tpg;
 		if (tmr_nacl && tmr_tpg) {
 			pr_debug("LUN_RESET: TMR caller fabric: %s"
 				" initiator port %s\n",
 				tmr_tpg->se_tpg_tfo->fabric_name,
 				tmr_nacl->initiatorname);
 		}
 	}
 	pr_debug("LUN_RESET: %s starting for [%s], tas: %d\n",
 		(preempt_and_abort_list) ? "Preempt" : "TMR",
 		dev->transport->name, tas);

 	core_tmr_drain_tmr_list(dev, tmr, preempt_and_abort_list);
 	core_tmr_drain_state_list(dev, prout_cmd, tmr_sess, tas,
 				preempt_and_abort_list);

 	/*
 	 * Clear any legacy SPC-2 reservation when called during
 	 * LOGICAL UNIT RESET
 	 */
 	if (!preempt_and_abort_list &&
 	     (dev->dev_reservation_flags & DRF_SPC2_RESERVATIONS)) {
 		spin_lock(&dev->dev_reservation_lock);
 		dev->reservation_holder = NULL;
 		dev->dev_reservation_flags &= ~DRF_SPC2_RESERVATIONS;
 		spin_unlock(&dev->dev_reservation_lock);
 		pr_debug("LUN_RESET: SCSI-2 Released reservation\n");
 	}

 	atomic_long_inc(&dev->num_resets);

 	pr_debug("LUN_RESET: %s for [%s] Complete\n",
 			(preempt_and_abort_list) ? "Preempt" : "TMR",
 			dev->transport->name);
 	return 0;
 }
	/*******************************************************************************
	* Filename: target_core_tmr.c
	*
	* This file contains SPC-3 task management infrastructure
	*
	* (c) Copyright 2009-2013 Datera, Inc.
	*
	* Nicholas A. Bellinger <nab@kernel.org>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	*
	******************************************************************************/

	#include <linux/slab.h>
	#include <linux/spinlock.h>
	#include <linux/list.h>
	#include <linux/export.h>

	#include <target/target_core_base.h>
	#include <target/target_core_backend.h>
	#include <target/target_core_fabric.h>

	#include "target_core_internal.h"
	#include "target_core_alua.h"
	#include "target_core_pr.h"

	int core_tmr_alloc_req(
	struct se_cmd *se_cmd,
	void *fabric_tmr_ptr,
	u8 function,
	gfp_t gfp_flags)
	{
	struct se_tmr_req *tmr;

	tmr = kzalloc(sizeof(struct se_tmr_req), gfp_flags);
	if (!tmr) {
	pr_err("Unable to allocate struct se_tmr_req\n");
	return -ENOMEM;
	}

	se_cmd->se_cmd_flags \|= SCF_SCSI_TMR_CDB;
	se_cmd->se_tmr_req = tmr;
	tmr->task_cmd = se_cmd;
	tmr->fabric_tmr_ptr = fabric_tmr_ptr;
	tmr->function = function;
	INIT_LIST_HEAD(&tmr->tmr_list);

	return 0;
	}
	EXPORT_SYMBOL(core_tmr_alloc_req);

	void core_tmr_release_req(struct se_tmr_req *tmr)
	{
	struct se_device *dev = tmr->tmr_dev;
	unsigned long flags;

	if (dev) {
	spin_lock_irqsave(&dev->se_tmr_lock, flags);
	list_del_init(&tmr->tmr_list);
	spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
	}

	kfree(tmr);
	}

	static int target_check_cdb_and_preempt(struct list_head *list,
	struct se_cmd *cmd)
	{
	struct t10_pr_registration *reg;

	if (!list)
	return 0;
	list_for_each_entry(reg, list, pr_reg_abort_list) {
	if (reg->pr_res_key == cmd->pr_res_key)
	return 0;
	}

	return 1;
	}

	static bool __target_check_io_state(struct se_cmd *se_cmd,
	struct se_session *tmr_sess, int tas)
	{
	struct se_session *sess = se_cmd->se_sess;

	assert_spin_locked(&sess->sess_cmd_lock);
	WARN_ON_ONCE(!irqs_disabled());
	/*
	* If command already reached CMD_T_COMPLETE state within
	* target_complete_cmd() or CMD_T_FABRIC_STOP due to shutdown,
	* this se_cmd has been passed to fabric driver and will
	* not be aborted.
	*
	* Otherwise, obtain a local se_cmd->cmd_kref now for TMR
	* ABORT_TASK + LUN_RESET for CMD_T_ABORTED processing as
	* long as se_cmd->cmd_kref is still active unless zero.
	*/
	spin_lock(&se_cmd->t_state_lock);
	if (se_cmd->transport_state & (CMD_T_COMPLETE \| CMD_T_FABRIC_STOP)) {
	pr_debug("Attempted to abort io tag: %llu already complete or"
	" fabric stop, skipping\n", se_cmd->tag);
	spin_unlock(&se_cmd->t_state_lock);
	return false;
	}
	se_cmd->transport_state \|= CMD_T_ABORTED;

	if ((tmr_sess != se_cmd->se_sess) && tas)
	se_cmd->transport_state \|= CMD_T_TAS;

	spin_unlock(&se_cmd->t_state_lock);

	return kref_get_unless_zero(&se_cmd->cmd_kref);
	}

	void core_tmr_abort_task(
	struct se_device *dev,
	struct se_tmr_req *tmr,
	struct se_session *se_sess)
	{
	struct se_cmd *se_cmd;
	unsigned long flags;
	u64 ref_tag;

	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
	list_for_each_entry(se_cmd, &se_sess->sess_cmd_list, se_cmd_list) {

	if (dev != se_cmd->se_dev)
	continue;

	/* skip task management functions, including tmr->task_cmd */
	if (se_cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
	continue;

	ref_tag = se_cmd->tag;
	if (tmr->ref_task_tag != ref_tag)
	continue;

	printk("ABORT_TASK: Found referenced %s task_tag: %llu\n",
	se_cmd->se_tfo->fabric_name, ref_tag);

	if (!__target_check_io_state(se_cmd, se_sess,
	dev->dev_attrib.emulate_tas))
	continue;

	spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

	/*
	* Ensure that this ABORT request is visible to the LU RESET
	* code.
	*/
	if (!tmr->tmr_dev)
	WARN_ON_ONCE(transport_lookup_tmr_lun(tmr->task_cmd,
	se_cmd->orig_fe_lun) < 0);

	target_put_cmd_and_wait(se_cmd);

	printk("ABORT_TASK: Sending TMR_FUNCTION_COMPLETE for"
	" ref_tag: %llu\n", ref_tag);
	tmr->response = TMR_FUNCTION_COMPLETE;
	atomic_long_inc(&dev->aborts_complete);
	return;
	}
	spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

	printk("ABORT_TASK: Sending TMR_TASK_DOES_NOT_EXIST for ref_tag: %lld\n",
	tmr->ref_task_tag);
	tmr->response = TMR_TASK_DOES_NOT_EXIST;
	atomic_long_inc(&dev->aborts_no_task);
	}

	static void core_tmr_drain_tmr_list(
	struct se_device *dev,
	struct se_tmr_req *tmr,
	struct list_head *preempt_and_abort_list)
	{
	LIST_HEAD(drain_tmr_list);
	struct se_session *sess;
	struct se_tmr_req tmr_p, tmr_pp;
	struct se_cmd *cmd;
	unsigned long flags;
	bool rc;
	/*
	* Release all pending and outgoing TMRs aside from the received
	* LUN_RESET tmr..
	*/
	spin_lock_irqsave(&dev->se_tmr_lock, flags);
	if (tmr)
	list_del_init(&tmr->tmr_list);
	list_for_each_entry_safe(tmr_p, tmr_pp, &dev->dev_tmr_list, tmr_list) {
	cmd = tmr_p->task_cmd;
	if (!cmd) {
	pr_err("Unable to locate struct se_cmd for TMR\n");
	continue;
	}
	/*
	* If this function was called with a valid pr_res_key
	* parameter (eg: for PROUT PREEMPT_AND_ABORT service action
	* skip non registration key matching TMRs.
	*/
	if (target_check_cdb_and_preempt(preempt_and_abort_list, cmd))
	continue;

	sess = cmd->se_sess;
	if (WARN_ON_ONCE(!sess))
	continue;

	spin_lock(&sess->sess_cmd_lock);
	rc = __target_check_io_state(cmd, sess, 0);
	spin_unlock(&sess->sess_cmd_lock);

	if (!rc) {
	printk("LUN_RESET TMR: non-zero kref_get_unless_zero\n");
	continue;
	}

	list_move_tail(&tmr_p->tmr_list, &drain_tmr_list);
	}
	spin_unlock_irqrestore(&dev->se_tmr_lock, flags);

	list_for_each_entry_safe(tmr_p, tmr_pp, &drain_tmr_list, tmr_list) {
	list_del_init(&tmr_p->tmr_list);
	cmd = tmr_p->task_cmd;

	pr_debug("LUN_RESET: %s releasing TMR %p Function: 0x%02x,"
	" Response: 0x%02x, t_state: %d\n",
	(preempt_and_abort_list) ? "Preempt" : "", tmr_p,
	tmr_p->function, tmr_p->response, cmd->t_state);

	target_put_cmd_and_wait(cmd);
	}
	}

	/**
	* core_tmr_drain_state_list() - abort SCSI commands associated with a device
	*
	* @dev: Device for which to abort outstanding SCSI commands.
	* @prout_cmd: Pointer to the SCSI PREEMPT AND ABORT if this function is called
	* to realize the PREEMPT AND ABORT functionality.
	* @tmr_sess: Session through which the LUN RESET has been received.
	* @tas: Task Aborted Status (TAS) bit from the SCSI control mode page.
	* A quote from SPC-4, paragraph "7.5.10 Control mode page":
	* "A task aborted status (TAS) bit set to zero specifies that
	* aborted commands shall be terminated by the device server
	* without any response to the application client. A TAS bit set
	* to one specifies that commands aborted by the actions of an I_T
	* nexus other than the I_T nexus on which the command was
	* received shall be completed with TASK ABORTED status."
	* @preempt_and_abort_list: For the PREEMPT AND ABORT functionality, a list
	* with registrations that will be preempted.
	*/
	static void core_tmr_drain_state_list(
	struct se_device *dev,
	struct se_cmd *prout_cmd,
	struct se_session *tmr_sess,
	int tas,
	struct list_head *preempt_and_abort_list)
	{
	LIST_HEAD(drain_task_list);
	struct se_session *sess;
	struct se_cmd cmd, next;
	unsigned long flags;
	int rc;

	/*
	* Complete outstanding commands with TASK_ABORTED SAM status.
	*
	* This is following sam4r17, section 5.6 Aborting commands, Table 38
	* for TMR LUN_RESET:
	*
	* a) "Yes" indicates that each command that is aborted on an I_T nexus
	* other than the one that caused the SCSI device condition is
	* completed with TASK ABORTED status, if the TAS bit is set to one in
	* the Control mode page (see SPC-4). "No" indicates that no status is
	* returned for aborted commands.
	*
	* d) If the logical unit reset is caused by a particular I_T nexus
	* (e.g., by a LOGICAL UNIT RESET task management function), then "yes"
	* (TASK_ABORTED status) applies.
	*
	* Otherwise (e.g., if triggered by a hard reset), "no"
	* (no TASK_ABORTED SAM status) applies.
	*
	* Note that this seems to be independent of TAS (Task Aborted Status)
	* in the Control Mode Page.
	*/
	spin_lock_irqsave(&dev->execute_task_lock, flags);
	list_for_each_entry_safe(cmd, next, &dev->state_list, state_list) {
	/*
	* For PREEMPT_AND_ABORT usage, only process commands
	* with a matching reservation key.
	*/
	if (target_check_cdb_and_preempt(preempt_and_abort_list, cmd))
	continue;

	/*
	* Not aborting PROUT PREEMPT_AND_ABORT CDB..
	*/
	if (prout_cmd == cmd)
	continue;

	sess = cmd->se_sess;
	if (WARN_ON_ONCE(!sess))
	continue;

	spin_lock(&sess->sess_cmd_lock);
	rc = __target_check_io_state(cmd, tmr_sess, tas);
	spin_unlock(&sess->sess_cmd_lock);
	if (!rc)
	continue;

	list_move_tail(&cmd->state_list, &drain_task_list);
	cmd->state_active = false;
	}
	spin_unlock_irqrestore(&dev->execute_task_lock, flags);

	while (!list_empty(&drain_task_list)) {
	cmd = list_entry(drain_task_list.next, struct se_cmd, state_list);
	list_del_init(&cmd->state_list);

	target_show_cmd("LUN_RESET: ", cmd);
	pr_debug("LUN_RESET: ITT[0x%08llx] - %s pr_res_key: 0x%016Lx\n",
	cmd->tag, (preempt_and_abort_list) ? "preempt" : "",
	cmd->pr_res_key);

	target_put_cmd_and_wait(cmd);
	}
	}

	int core_tmr_lun_reset(
	struct se_device *dev,
	struct se_tmr_req *tmr,
	struct list_head *preempt_and_abort_list,
	struct se_cmd *prout_cmd)
	{
	struct se_node_acl *tmr_nacl = NULL;
	struct se_portal_group *tmr_tpg = NULL;
	struct se_session *tmr_sess = NULL;
	int tas;
	/*
	* TASK_ABORTED status bit, this is configurable via ConfigFS
	* struct se_device attributes. spc4r17 section 7.4.6 Control mode page
	*
	* A task aborted status (TAS) bit set to zero specifies that aborted
	* tasks shall be terminated by the device server without any response
	* to the application client. A TAS bit set to one specifies that tasks
	* aborted by the actions of an I_T nexus other than the I_T nexus on
	* which the command was received shall be completed with TASK ABORTED
	* status (see SAM-4).
	*/
	tas = dev->dev_attrib.emulate_tas;
	/*
	* Determine if this se_tmr is coming from a $FABRIC_MOD
	* or struct se_device passthrough..
	*/
	if (tmr && tmr->task_cmd && tmr->task_cmd->se_sess) {
	tmr_sess = tmr->task_cmd->se_sess;
	tmr_nacl = tmr_sess->se_node_acl;
	tmr_tpg = tmr_sess->se_tpg;
	if (tmr_nacl && tmr_tpg) {
	pr_debug("LUN_RESET: TMR caller fabric: %s"
	" initiator port %s\n",
	tmr_tpg->se_tpg_tfo->fabric_name,
	tmr_nacl->initiatorname);
	}
	}
	pr_debug("LUN_RESET: %s starting for [%s], tas: %d\n",
	(preempt_and_abort_list) ? "Preempt" : "TMR",
	dev->transport->name, tas);

	core_tmr_drain_tmr_list(dev, tmr, preempt_and_abort_list);
	core_tmr_drain_state_list(dev, prout_cmd, tmr_sess, tas,
	preempt_and_abort_list);

	/*
	* Clear any legacy SPC-2 reservation when called during
	* LOGICAL UNIT RESET
	*/
	if (!preempt_and_abort_list &&
	(dev->dev_reservation_flags & DRF_SPC2_RESERVATIONS)) {
	spin_lock(&dev->dev_reservation_lock);
	dev->reservation_holder = NULL;
	dev->dev_reservation_flags &= ~DRF_SPC2_RESERVATIONS;
	spin_unlock(&dev->dev_reservation_lock);
	pr_debug("LUN_RESET: SCSI-2 Released reservation\n");
	}

	atomic_long_inc(&dev->num_resets);

	pr_debug("LUN_RESET: %s for [%s] Complete\n",
	(preempt_and_abort_list) ? "Preempt" : "TMR",
	dev->transport->name);
	return 0;
	}