/*******************************************************************************
 * 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 core_tmr_handle_tas_abort(struct se_cmd *cmd, int tas)
{
        unsigned long flags;
        bool remove = true, send_tas;
        /*
         * TASK ABORTED status (TAS) bit support
         */
        spin_lock_irqsave(&cmd->t_state_lock, flags);
        send_tas = (cmd->transport_state & CMD_T_TAS);
        spin_unlock_irqrestore(&cmd->t_state_lock, flags);

        if (send_tas) {
                remove = false;
                transport_send_task_abort(cmd);
        }

        return transport_cmd_finish_abort(cmd, remove);
}

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;
        }
        if (sess->sess_tearing_down || se_cmd->cmd_wait_set) {
                pr_debug("Attempted to abort io tag: %llu already shutdown,"
                        " 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->get_fabric_name(), ref_tag);

                if (!__target_check_io_state(se_cmd, se_sess, 0))
                        continue;

                list_del_init(&se_cmd->se_cmd_list);
                spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

                cancel_work_sync(&se_cmd->work);
                transport_wait_for_tasks(se_cmd);

                if (!transport_cmd_finish_abort(se_cmd, true))
                        target_put_sess_cmd(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);
        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);
                spin_lock(&cmd->t_state_lock);
                if (!(cmd->transport_state & CMD_T_ACTIVE) ||
                     (cmd->transport_state & CMD_T_FABRIC_STOP)) {
                        spin_unlock(&cmd->t_state_lock);
                        spin_unlock(&sess->sess_cmd_lock);
                        continue;
                }
                if (cmd->t_state == TRANSPORT_ISTATE_PROCESSING) {
                        spin_unlock(&cmd->t_state_lock);
                        spin_unlock(&sess->sess_cmd_lock);
                        continue;
                }
                if (sess->sess_tearing_down || cmd->cmd_wait_set) {
                        spin_unlock(&cmd->t_state_lock);
                        spin_unlock(&sess->sess_cmd_lock);
                        continue;
                }
                cmd->transport_state |= CMD_T_ABORTED;
                spin_unlock(&cmd->t_state_lock);

                rc = kref_get_unless_zero(&cmd->cmd_kref);
                if (!rc) {
                        printk("LUN_RESET TMR: non-zero kref_get_unless_zero\n");
                        spin_unlock(&sess->sess_cmd_lock);
                        continue;
                }
                spin_unlock(&sess->sess_cmd_lock);

                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);

                cancel_work_sync(&cmd->work);
                transport_wait_for_tasks(cmd);

                if (!transport_cmd_finish_abort(cmd, 1))
                        target_put_sess_cmd(cmd);
        }
}

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);

                /*
                 * If the command may be queued onto a workqueue cancel it now.
                 *
                 * This is equivalent to removal from the execute queue in the
                 * loop above, but we do it down here given that
                 * cancel_work_sync may block.
                 */
                cancel_work_sync(&cmd->work);
                transport_wait_for_tasks(cmd);

                if (!core_tmr_handle_tas_abort(cmd, tas))
                        target_put_sess_cmd(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->get_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->dev_reserved_node_acl = 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;
}