target_core_pr.c

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/*******************************************************************************
 * Filename:  target_core_pr.c
 *
 * This file contains SPC-3 compliant persistent reservations and
 * legacy SPC-2 reservations with compatible reservation handling (CRH=1)
 *
 * Copyright (c) 2009, 2010 Rising Tide Systems
 * Copyright (c) 2009, 2010 Linux-iSCSI.org
 *
 * Nicholas A. Bellinger <[email protected]>
 *
 * 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 <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <asm/unaligned.h>

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

#include "target_core_internal.h"
#include "target_core_pr.h"
#include "target_core_ua.h"

/*
 * Used for Specify Initiator Ports Capable Bit (SPEC_I_PT)
 */
struct pr_transport_id_holder {
    int dest_local_nexus;
    struct t10_pr_registration *dest_pr_reg;
    struct se_portal_group *dest_tpg;
    struct se_node_acl *dest_node_acl;
    struct se_dev_entry *dest_se_deve;
    struct list_head dest_list;
};

int core_pr_dump_initiator_port(
    struct t10_pr_registration *pr_reg,
    char *buf,
    u32 size)
{
    if (!pr_reg->isid_present_at_reg)
        return 0;

    snprintf(buf, size, ",i,0x%s", &pr_reg->pr_reg_isid[0]);
    return 1;
}

static void __core_scsi3_complete_pro_release(struct se_device *, struct se_node_acl *,
            struct t10_pr_registration *, int);

static int core_scsi2_reservation_seq_non_holder(
    struct se_cmd *cmd,
    unsigned char *cdb,
    u32 pr_reg_type)
{
    switch (cdb[0]) {
    case INQUIRY:
    case RELEASE:
    case RELEASE_10:
        return 0;
    default:
        return 1;
    }

    return 1;
}

static int core_scsi2_reservation_check(struct se_cmd *cmd, u32 *pr_reg_type)
{
    struct se_device *dev = cmd->se_dev;
    struct se_session *sess = cmd->se_sess;
    int ret;

    if (!sess)
        return 0;

    spin_lock(&dev->dev_reservation_lock);
    if (!dev->dev_reserved_node_acl || !sess) {
        spin_unlock(&dev->dev_reservation_lock);
        return 0;
    }
    if (dev->dev_reserved_node_acl != sess->se_node_acl) {
        spin_unlock(&dev->dev_reservation_lock);
        return -EINVAL;
    }
    if (!(dev->dev_flags & DF_SPC2_RESERVATIONS_WITH_ISID)) {
        spin_unlock(&dev->dev_reservation_lock);
        return 0;
    }
    ret = (dev->dev_res_bin_isid == sess->sess_bin_isid) ? 0 : -EINVAL;
    spin_unlock(&dev->dev_reservation_lock);

    return ret;
}

static struct t10_pr_registration *core_scsi3_locate_pr_reg(struct se_device *,
                    struct se_node_acl *, struct se_session *);
static void core_scsi3_put_pr_reg(struct t10_pr_registration *);

static int target_check_scsi2_reservation_conflict(struct se_cmd *cmd)
{
    struct se_session *se_sess = cmd->se_sess;
    struct se_subsystem_dev *su_dev = cmd->se_dev->se_sub_dev;
    struct t10_pr_registration *pr_reg;
    struct t10_reservation *pr_tmpl = &su_dev->t10_pr;
    int crh = (su_dev->t10_pr.res_type == SPC3_PERSISTENT_RESERVATIONS);
    int conflict = 0;

    if (!crh)
        return -EINVAL;

    pr_reg = core_scsi3_locate_pr_reg(cmd->se_dev, se_sess->se_node_acl,
            se_sess);
    if (pr_reg) {
        /*
         * From spc4r17 5.7.3 Exceptions to SPC-2 RESERVE and RELEASE
         * behavior
         *
         * A RESERVE(6) or RESERVE(10) command shall complete with GOOD
         * status, but no reservation shall be established and the
         * persistent reservation shall not be changed, if the command
         * is received from a) and b) below.
         *
         * A RELEASE(6) or RELEASE(10) command shall complete with GOOD
         * status, but the persistent reservation shall not be released,
         * if the command is received from a) and b)
         *
         * a) An I_T nexus that is a persistent reservation holder; or
         * b) An I_T nexus that is registered if a registrants only or
         *    all registrants type persistent reservation is present.
         *
         * In all other cases, a RESERVE(6) command, RESERVE(10) command,
         * RELEASE(6) command, or RELEASE(10) command shall be processed
         * as defined in SPC-2.
         */
        if (pr_reg->pr_res_holder) {
            core_scsi3_put_pr_reg(pr_reg);
            return 1;
        }
        if ((pr_reg->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_REGONLY) ||
            (pr_reg->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_REGONLY) ||
            (pr_reg->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG) ||
            (pr_reg->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG)) {
            core_scsi3_put_pr_reg(pr_reg);
            return 1;
        }
        core_scsi3_put_pr_reg(pr_reg);
        conflict = 1;
    } else {
        /*
         * Following spc2r20 5.5.1 Reservations overview:
         *
         * If a logical unit has executed a PERSISTENT RESERVE OUT
         * command with the REGISTER or the REGISTER AND IGNORE
         * EXISTING KEY service action and is still registered by any
         * initiator, all RESERVE commands and all RELEASE commands
         * regardless of initiator shall conflict and shall terminate
         * with a RESERVATION CONFLICT status.
         */
        spin_lock(&pr_tmpl->registration_lock);
        conflict = (list_empty(&pr_tmpl->registration_list)) ? 0 : 1;
        spin_unlock(&pr_tmpl->registration_lock);
    }

    if (conflict) {
        pr_err("Received legacy SPC-2 RESERVE/RELEASE"
            " while active SPC-3 registrations exist,"
            " returning RESERVATION_CONFLICT\n");
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EBUSY;
    }

    return 0;
}

int target_scsi2_reservation_release(struct se_cmd *cmd)
{
    struct se_device *dev = cmd->se_dev;
    struct se_session *sess = cmd->se_sess;
    struct se_portal_group *tpg;
    int ret = 0, rc;

    if (!sess || !sess->se_tpg)
        goto out;
    rc = target_check_scsi2_reservation_conflict(cmd);
    if (rc == 1)
        goto out;
    else if (rc < 0) {
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        ret = -EINVAL;
        goto out;
    }

    ret = 0;
    spin_lock(&dev->dev_reservation_lock);
    if (!dev->dev_reserved_node_acl || !sess)
        goto out_unlock;

    if (dev->dev_reserved_node_acl != sess->se_node_acl)
        goto out_unlock;

    if (dev->dev_res_bin_isid != sess->sess_bin_isid)
        goto out_unlock;

    dev->dev_reserved_node_acl = NULL;
    dev->dev_flags &= ~DF_SPC2_RESERVATIONS;
    if (dev->dev_flags & DF_SPC2_RESERVATIONS_WITH_ISID) {
        dev->dev_res_bin_isid = 0;
        dev->dev_flags &= ~DF_SPC2_RESERVATIONS_WITH_ISID;
    }
    tpg = sess->se_tpg;
    pr_debug("SCSI-2 Released reservation for %s LUN: %u ->"
        " MAPPED LUN: %u for %s\n", tpg->se_tpg_tfo->get_fabric_name(),
        cmd->se_lun->unpacked_lun, cmd->se_deve->mapped_lun,
        sess->se_node_acl->initiatorname);

out_unlock:
    spin_unlock(&dev->dev_reservation_lock);
out:
    if (!ret)
        target_complete_cmd(cmd, GOOD);
    return ret;
}

int target_scsi2_reservation_reserve(struct se_cmd *cmd)
{
    struct se_device *dev = cmd->se_dev;
    struct se_session *sess = cmd->se_sess;
    struct se_portal_group *tpg;
    int ret = 0, rc;

    if ((cmd->t_task_cdb[1] & 0x01) &&
        (cmd->t_task_cdb[1] & 0x02)) {
        pr_err("LongIO and Obselete Bits set, returning"
                " ILLEGAL_REQUEST\n");
        cmd->scsi_sense_reason = TCM_UNSUPPORTED_SCSI_OPCODE;
        ret = -EINVAL;
        goto out;
    }
    /*
     * This is currently the case for target_core_mod passthrough struct se_cmd
     * ops
     */
    if (!sess || !sess->se_tpg)
        goto out;
    rc = target_check_scsi2_reservation_conflict(cmd);
    if (rc == 1)
        goto out;
    else if (rc < 0) {
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        ret = -EINVAL;
        goto out;
    }

    ret = 0;
    tpg = sess->se_tpg;
    spin_lock(&dev->dev_reservation_lock);
    if (dev->dev_reserved_node_acl &&
       (dev->dev_reserved_node_acl != sess->se_node_acl)) {
        pr_err("SCSI-2 RESERVATION CONFLIFT for %s fabric\n",
            tpg->se_tpg_tfo->get_fabric_name());
        pr_err("Original reserver LUN: %u %s\n",
            cmd->se_lun->unpacked_lun,
            dev->dev_reserved_node_acl->initiatorname);
        pr_err("Current attempt - LUN: %u -> MAPPED LUN: %u"
            " from %s \n", cmd->se_lun->unpacked_lun,
            cmd->se_deve->mapped_lun,
            sess->se_node_acl->initiatorname);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        ret = -EINVAL;
        goto out_unlock;
    }

    dev->dev_reserved_node_acl = sess->se_node_acl;
    dev->dev_flags |= DF_SPC2_RESERVATIONS;
    if (sess->sess_bin_isid != 0) {
        dev->dev_res_bin_isid = sess->sess_bin_isid;
        dev->dev_flags |= DF_SPC2_RESERVATIONS_WITH_ISID;
    }
    pr_debug("SCSI-2 Reserved %s LUN: %u -> MAPPED LUN: %u"
        " for %s\n", tpg->se_tpg_tfo->get_fabric_name(),
        cmd->se_lun->unpacked_lun, cmd->se_deve->mapped_lun,
        sess->se_node_acl->initiatorname);

out_unlock:
    spin_unlock(&dev->dev_reservation_lock);
out:
    if (!ret)
        target_complete_cmd(cmd, GOOD);
    return ret;
}


/*
 * Begin SPC-3/SPC-4 Persistent Reservations emulation support
 *
 * This function is called by those initiator ports who are *NOT*
 * the active PR reservation holder when a reservation is present.
 */
static int core_scsi3_pr_seq_non_holder(
    struct se_cmd *cmd,
    unsigned char *cdb,
    u32 pr_reg_type)
{
    struct se_dev_entry *se_deve;
    struct se_session *se_sess = cmd->se_sess;
    int other_cdb = 0, ignore_reg;
    int registered_nexus = 0, ret = 1; /* Conflict by default */
    int all_reg = 0, reg_only = 0; /* ALL_REG, REG_ONLY */
    int we = 0; /* Write Exclusive */
    int legacy = 0; /* Act like a legacy device and return
             * RESERVATION CONFLICT on some CDBs */
    /*
     * A legacy SPC-2 reservation is being held.
     */
    if (cmd->se_dev->dev_flags & DF_SPC2_RESERVATIONS)
        return core_scsi2_reservation_seq_non_holder(cmd,
                    cdb, pr_reg_type);

    se_deve = se_sess->se_node_acl->device_list[cmd->orig_fe_lun];
    /*
     * Determine if the registration should be ignored due to
     * non-matching ISIDs in core_scsi3_pr_reservation_check().
     */
    ignore_reg = (pr_reg_type & 0x80000000);
    if (ignore_reg)
        pr_reg_type &= ~0x80000000;

    switch (pr_reg_type) {
    case PR_TYPE_WRITE_EXCLUSIVE:
        we = 1;
    case PR_TYPE_EXCLUSIVE_ACCESS:
        /*
         * Some commands are only allowed for the persistent reservation
         * holder.
         */
        if ((se_deve->def_pr_registered) && !(ignore_reg))
            registered_nexus = 1;
        break;
    case PR_TYPE_WRITE_EXCLUSIVE_REGONLY:
        we = 1;
    case PR_TYPE_EXCLUSIVE_ACCESS_REGONLY:
        /*
         * Some commands are only allowed for registered I_T Nexuses.
         */
        reg_only = 1;
        if ((se_deve->def_pr_registered) && !(ignore_reg))
            registered_nexus = 1;
        break;
    case PR_TYPE_WRITE_EXCLUSIVE_ALLREG:
        we = 1;
    case PR_TYPE_EXCLUSIVE_ACCESS_ALLREG:
        /*
         * Each registered I_T Nexus is a reservation holder.
         */
        all_reg = 1;
        if ((se_deve->def_pr_registered) && !(ignore_reg))
            registered_nexus = 1;
        break;
    default:
        return -EINVAL;
    }
    /*
     * Referenced from spc4r17 table 45 for *NON* PR holder access
     */
    switch (cdb[0]) {
    case SECURITY_PROTOCOL_IN:
        if (registered_nexus)
            return 0;
        ret = (we) ? 0 : 1;
        break;
    case MODE_SENSE:
    case MODE_SENSE_10:
    case READ_ATTRIBUTE:
    case READ_BUFFER:
    case RECEIVE_DIAGNOSTIC:
        if (legacy) {
            ret = 1;
            break;
        }
        if (registered_nexus) {
            ret = 0;
            break;
        }
        ret = (we) ? 0 : 1; /* Allowed Write Exclusive */
        break;
    case PERSISTENT_RESERVE_OUT:
        /*
         * This follows PERSISTENT_RESERVE_OUT service actions that
         * are allowed in the presence of various reservations.
         * See spc4r17, table 46
         */
        switch (cdb[1] & 0x1f) {
        case PRO_CLEAR:
        case PRO_PREEMPT:
        case PRO_PREEMPT_AND_ABORT:
            ret = (registered_nexus) ? 0 : 1;
            break;
        case PRO_REGISTER:
        case PRO_REGISTER_AND_IGNORE_EXISTING_KEY:
            ret = 0;
            break;
        case PRO_REGISTER_AND_MOVE:
        case PRO_RESERVE:
            ret = 1;
            break;
        case PRO_RELEASE:
            ret = (registered_nexus) ? 0 : 1;
            break;
        default:
            pr_err("Unknown PERSISTENT_RESERVE_OUT service"
                " action: 0x%02x\n", cdb[1] & 0x1f);
            return -EINVAL;
        }
        break;
    case RELEASE:
    case RELEASE_10:
        /* Handled by CRH=1 in target_scsi2_reservation_release() */
        ret = 0;
        break;
    case RESERVE:
    case RESERVE_10:
        /* Handled by CRH=1 in target_scsi2_reservation_reserve() */
        ret = 0;
        break;
    case TEST_UNIT_READY:
        ret = (legacy) ? 1 : 0; /* Conflict for legacy */
        break;
    case MAINTENANCE_IN:
        switch (cdb[1] & 0x1f) {
        case MI_MANAGEMENT_PROTOCOL_IN:
            if (registered_nexus) {
                ret = 0;
                break;
            }
            ret = (we) ? 0 : 1; /* Allowed Write Exclusive */
            break;
        case MI_REPORT_SUPPORTED_OPERATION_CODES:
        case MI_REPORT_SUPPORTED_TASK_MANAGEMENT_FUNCTIONS:
            if (legacy) {
                ret = 1;
                break;
            }
            if (registered_nexus) {
                ret = 0;
                break;
            }
            ret = (we) ? 0 : 1; /* Allowed Write Exclusive */
            break;
        case MI_REPORT_ALIASES:
        case MI_REPORT_IDENTIFYING_INFORMATION:
        case MI_REPORT_PRIORITY:
        case MI_REPORT_TARGET_PGS:
        case MI_REPORT_TIMESTAMP:
            ret = 0; /* Allowed */
            break;
        default:
            pr_err("Unknown MI Service Action: 0x%02x\n",
                (cdb[1] & 0x1f));
            return -EINVAL;
        }
        break;
    case ACCESS_CONTROL_IN:
    case ACCESS_CONTROL_OUT:
    case INQUIRY:
    case LOG_SENSE:
    case READ_MEDIA_SERIAL_NUMBER:
    case REPORT_LUNS:
    case REQUEST_SENSE:
    case PERSISTENT_RESERVE_IN:
        ret = 0; /*/ Allowed CDBs */
        break;
    default:
        other_cdb = 1;
        break;
    }
    /*
     * Case where the CDB is explicitly allowed in the above switch
     * statement.
     */
    if (!ret && !other_cdb) {
        pr_debug("Allowing explict CDB: 0x%02x for %s"
            " reservation holder\n", cdb[0],
            core_scsi3_pr_dump_type(pr_reg_type));

        return ret;
    }
    /*
     * Check if write exclusive initiator ports *NOT* holding the
     * WRITE_EXCLUSIVE_* reservation.
     */
    if (we && !registered_nexus) {
        if (cmd->data_direction == DMA_TO_DEVICE) {
            /*
             * Conflict for write exclusive
             */
            pr_debug("%s Conflict for unregistered nexus"
                " %s CDB: 0x%02x to %s reservation\n",
                transport_dump_cmd_direction(cmd),
                se_sess->se_node_acl->initiatorname, cdb[0],
                core_scsi3_pr_dump_type(pr_reg_type));
            return 1;
        } else {
            /*
             * Allow non WRITE CDBs for all Write Exclusive
             * PR TYPEs to pass for registered and
             * non-registered_nexuxes NOT holding the reservation.
             *
             * We only make noise for the unregisterd nexuses,
             * as we expect registered non-reservation holding
             * nexuses to issue CDBs.
             */

            if (!registered_nexus) {
                pr_debug("Allowing implict CDB: 0x%02x"
                    " for %s reservation on unregistered"
                    " nexus\n", cdb[0],
                    core_scsi3_pr_dump_type(pr_reg_type));
            }

            return 0;
        }
    } else if ((reg_only) || (all_reg)) {
        if (registered_nexus) {
            /*
             * For PR_*_REG_ONLY and PR_*_ALL_REG reservations,
             * allow commands from registered nexuses.
             */

            pr_debug("Allowing implict CDB: 0x%02x for %s"
                " reservation\n", cdb[0],
                core_scsi3_pr_dump_type(pr_reg_type));

            return 0;
        }
    }
    pr_debug("%s Conflict for %sregistered nexus %s CDB: 0x%2x"
        " for %s reservation\n", transport_dump_cmd_direction(cmd),
        (registered_nexus) ? "" : "un",
        se_sess->se_node_acl->initiatorname, cdb[0],
        core_scsi3_pr_dump_type(pr_reg_type));

    return 1; /* Conflict by default */
}

static u32 core_scsi3_pr_generation(struct se_device *dev)
{
    struct se_subsystem_dev *su_dev = dev->se_sub_dev;
    u32 prg;
    /*
     * PRGeneration field shall contain the value of a 32-bit wrapping
     * counter mainted by the device server.
     *
     * Note that this is done regardless of Active Persist across
     * Target PowerLoss (APTPL)
     *
     * See spc4r17 section 6.3.12 READ_KEYS service action
     */
    spin_lock(&dev->dev_reservation_lock);
    prg = su_dev->t10_pr.pr_generation++;
    spin_unlock(&dev->dev_reservation_lock);

    return prg;
}

static int core_scsi3_pr_reservation_check(
    struct se_cmd *cmd,
    u32 *pr_reg_type)
{
    struct se_device *dev = cmd->se_dev;
    struct se_session *sess = cmd->se_sess;
    int ret;

    if (!sess)
        return 0;
    /*
     * A legacy SPC-2 reservation is being held.
     */
    if (dev->dev_flags & DF_SPC2_RESERVATIONS)
        return core_scsi2_reservation_check(cmd, pr_reg_type);

    spin_lock(&dev->dev_reservation_lock);
    if (!dev->dev_pr_res_holder) {
        spin_unlock(&dev->dev_reservation_lock);
        return 0;
    }
    *pr_reg_type = dev->dev_pr_res_holder->pr_res_type;
    cmd->pr_res_key = dev->dev_pr_res_holder->pr_res_key;
    if (dev->dev_pr_res_holder->pr_reg_nacl != sess->se_node_acl) {
        spin_unlock(&dev->dev_reservation_lock);
        return -EINVAL;
    }
    if (!dev->dev_pr_res_holder->isid_present_at_reg) {
        spin_unlock(&dev->dev_reservation_lock);
        return 0;
    }
    ret = (dev->dev_pr_res_holder->pr_reg_bin_isid ==
           sess->sess_bin_isid) ? 0 : -EINVAL;
    /*
     * Use bit in *pr_reg_type to notify ISID mismatch in
     * core_scsi3_pr_seq_non_holder().
     */
    if (ret != 0)
        *pr_reg_type |= 0x80000000;
    spin_unlock(&dev->dev_reservation_lock);

    return ret;
}

static struct t10_pr_registration *__core_scsi3_do_alloc_registration(
    struct se_device *dev,
    struct se_node_acl *nacl,
    struct se_dev_entry *deve,
    unsigned char *isid,
    u64 sa_res_key,
    int all_tg_pt,
    int aptpl)
{
    struct se_subsystem_dev *su_dev = dev->se_sub_dev;
    struct t10_pr_registration *pr_reg;

    pr_reg = kmem_cache_zalloc(t10_pr_reg_cache, GFP_ATOMIC);
    if (!pr_reg) {
        pr_err("Unable to allocate struct t10_pr_registration\n");
        return NULL;
    }

    pr_reg->pr_aptpl_buf = kzalloc(su_dev->t10_pr.pr_aptpl_buf_len,
                    GFP_ATOMIC);
    if (!pr_reg->pr_aptpl_buf) {
        pr_err("Unable to allocate pr_reg->pr_aptpl_buf\n");
        kmem_cache_free(t10_pr_reg_cache, pr_reg);
        return NULL;
    }

    INIT_LIST_HEAD(&pr_reg->pr_reg_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_abort_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_aptpl_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_atp_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_atp_mem_list);
    atomic_set(&pr_reg->pr_res_holders, 0);
    pr_reg->pr_reg_nacl = nacl;
    pr_reg->pr_reg_deve = deve;
    pr_reg->pr_res_mapped_lun = deve->mapped_lun;
    pr_reg->pr_aptpl_target_lun = deve->se_lun->unpacked_lun;
    pr_reg->pr_res_key = sa_res_key;
    pr_reg->pr_reg_all_tg_pt = all_tg_pt;
    pr_reg->pr_reg_aptpl = aptpl;
    pr_reg->pr_reg_tg_pt_lun = deve->se_lun;
    /*
     * If an ISID value for this SCSI Initiator Port exists,
     * save it to the registration now.
     */
    if (isid != NULL) {
        pr_reg->pr_reg_bin_isid = get_unaligned_be64(isid);
        snprintf(pr_reg->pr_reg_isid, PR_REG_ISID_LEN, "%s", isid);
        pr_reg->isid_present_at_reg = 1;
    }

    return pr_reg;
}

static int core_scsi3_lunacl_depend_item(struct se_dev_entry *);
static void core_scsi3_lunacl_undepend_item(struct se_dev_entry *);

/*
 * Function used for handling PR registrations for ALL_TG_PT=1 and ALL_TG_PT=0
 * modes.
 */
static struct t10_pr_registration *__core_scsi3_alloc_registration(
    struct se_device *dev,
    struct se_node_acl *nacl,
    struct se_dev_entry *deve,
    unsigned char *isid,
    u64 sa_res_key,
    int all_tg_pt,
    int aptpl)
{
    struct se_dev_entry *deve_tmp;
    struct se_node_acl *nacl_tmp;
    struct se_port *port, *port_tmp;
    struct target_core_fabric_ops *tfo = nacl->se_tpg->se_tpg_tfo;
    struct t10_pr_registration *pr_reg, *pr_reg_atp, *pr_reg_tmp, *pr_reg_tmp_safe;
    int ret;
    /*
     * Create a registration for the I_T Nexus upon which the
     * PROUT REGISTER was received.
     */
    pr_reg = __core_scsi3_do_alloc_registration(dev, nacl, deve, isid,
            sa_res_key, all_tg_pt, aptpl);
    if (!pr_reg)
        return NULL;
    /*
     * Return pointer to pr_reg for ALL_TG_PT=0
     */
    if (!all_tg_pt)
        return pr_reg;
    /*
     * Create list of matching SCSI Initiator Port registrations
     * for ALL_TG_PT=1
     */
    spin_lock(&dev->se_port_lock);
    list_for_each_entry_safe(port, port_tmp, &dev->dev_sep_list, sep_list) {
        atomic_inc(&port->sep_tg_pt_ref_cnt);
        smp_mb__after_atomic_inc();
        spin_unlock(&dev->se_port_lock);

        spin_lock_bh(&port->sep_alua_lock);
        list_for_each_entry(deve_tmp, &port->sep_alua_list,
                    alua_port_list) {
            /*
             * This pointer will be NULL for demo mode MappedLUNs
             * that have not been make explict via a ConfigFS
             * MappedLUN group for the SCSI Initiator Node ACL.
             */
            if (!deve_tmp->se_lun_acl)
                continue;

            nacl_tmp = deve_tmp->se_lun_acl->se_lun_nacl;
            /*
             * Skip the matching struct se_node_acl that is allocated
             * above..
             */
            if (nacl == nacl_tmp)
                continue;
            /*
             * Only perform PR registrations for target ports on
             * the same fabric module as the REGISTER w/ ALL_TG_PT=1
             * arrived.
             */
            if (tfo != nacl_tmp->se_tpg->se_tpg_tfo)
                continue;
            /*
             * Look for a matching Initiator Node ACL in ASCII format
             */
            if (strcmp(nacl->initiatorname, nacl_tmp->initiatorname))
                continue;

            atomic_inc(&deve_tmp->pr_ref_count);
            smp_mb__after_atomic_inc();
            spin_unlock_bh(&port->sep_alua_lock);
            /*
             * Grab a configfs group dependency that is released
             * for the exception path at label out: below, or upon
             * completion of adding ALL_TG_PT=1 registrations in
             * __core_scsi3_add_registration()
             */
            ret = core_scsi3_lunacl_depend_item(deve_tmp);
            if (ret < 0) {
                pr_err("core_scsi3_lunacl_depend"
                        "_item() failed\n");
                atomic_dec(&port->sep_tg_pt_ref_cnt);
                smp_mb__after_atomic_dec();
                atomic_dec(&deve_tmp->pr_ref_count);
                smp_mb__after_atomic_dec();
                goto out;
            }
            /*
             * Located a matching SCSI Initiator Port on a different
             * port, allocate the pr_reg_atp and attach it to the
             * pr_reg->pr_reg_atp_list that will be processed once
             * the original *pr_reg is processed in
             * __core_scsi3_add_registration()
             */
            pr_reg_atp = __core_scsi3_do_alloc_registration(dev,
                        nacl_tmp, deve_tmp, NULL,
                        sa_res_key, all_tg_pt, aptpl);
            if (!pr_reg_atp) {
                atomic_dec(&port->sep_tg_pt_ref_cnt);
                smp_mb__after_atomic_dec();
                atomic_dec(&deve_tmp->pr_ref_count);
                smp_mb__after_atomic_dec();
                core_scsi3_lunacl_undepend_item(deve_tmp);
                goto out;
            }

            list_add_tail(&pr_reg_atp->pr_reg_atp_mem_list,
                      &pr_reg->pr_reg_atp_list);
            spin_lock_bh(&port->sep_alua_lock);
        }
        spin_unlock_bh(&port->sep_alua_lock);

        spin_lock(&dev->se_port_lock);
        atomic_dec(&port->sep_tg_pt_ref_cnt);
        smp_mb__after_atomic_dec();
    }
    spin_unlock(&dev->se_port_lock);

    return pr_reg;
out:
    list_for_each_entry_safe(pr_reg_tmp, pr_reg_tmp_safe,
            &pr_reg->pr_reg_atp_list, pr_reg_atp_mem_list) {
        list_del(&pr_reg_tmp->pr_reg_atp_mem_list);
        core_scsi3_lunacl_undepend_item(pr_reg_tmp->pr_reg_deve);
        kmem_cache_free(t10_pr_reg_cache, pr_reg_tmp);
    }
    kmem_cache_free(t10_pr_reg_cache, pr_reg);
    return NULL;
}

int core_scsi3_alloc_aptpl_registration(
    struct t10_reservation *pr_tmpl,
    u64 sa_res_key,
    unsigned char *i_port,
    unsigned char *isid,
    u32 mapped_lun,
    unsigned char *t_port,
    u16 tpgt,
    u32 target_lun,
    int res_holder,
    int all_tg_pt,
    u8 type)
{
    struct t10_pr_registration *pr_reg;

    if (!i_port || !t_port || !sa_res_key) {
        pr_err("Illegal parameters for APTPL registration\n");
        return -EINVAL;
    }

    pr_reg = kmem_cache_zalloc(t10_pr_reg_cache, GFP_KERNEL);
    if (!pr_reg) {
        pr_err("Unable to allocate struct t10_pr_registration\n");
        return -ENOMEM;
    }
    pr_reg->pr_aptpl_buf = kzalloc(pr_tmpl->pr_aptpl_buf_len, GFP_KERNEL);

    INIT_LIST_HEAD(&pr_reg->pr_reg_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_abort_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_aptpl_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_atp_list);
    INIT_LIST_HEAD(&pr_reg->pr_reg_atp_mem_list);
    atomic_set(&pr_reg->pr_res_holders, 0);
    pr_reg->pr_reg_nacl = NULL;
    pr_reg->pr_reg_deve = NULL;
    pr_reg->pr_res_mapped_lun = mapped_lun;
    pr_reg->pr_aptpl_target_lun = target_lun;
    pr_reg->pr_res_key = sa_res_key;
    pr_reg->pr_reg_all_tg_pt = all_tg_pt;
    pr_reg->pr_reg_aptpl = 1;
    pr_reg->pr_reg_tg_pt_lun = NULL;
    pr_reg->pr_res_scope = 0; /* Always LUN_SCOPE */
    pr_reg->pr_res_type = type;
    /*
     * If an ISID value had been saved in APTPL metadata for this
     * SCSI Initiator Port, restore it now.
     */
    if (isid != NULL) {
        pr_reg->pr_reg_bin_isid = get_unaligned_be64(isid);
        snprintf(pr_reg->pr_reg_isid, PR_REG_ISID_LEN, "%s", isid);
        pr_reg->isid_present_at_reg = 1;
    }
    /*
     * Copy the i_port and t_port information from caller.
     */
    snprintf(pr_reg->pr_iport, PR_APTPL_MAX_IPORT_LEN, "%s", i_port);
    snprintf(pr_reg->pr_tport, PR_APTPL_MAX_TPORT_LEN, "%s", t_port);
    pr_reg->pr_reg_tpgt = tpgt;
    /*
     * Set pr_res_holder from caller, the pr_reg who is the reservation
     * holder will get it's pointer set in core_scsi3_aptpl_reserve() once
     * the Initiator Node LUN ACL from the fabric module is created for
     * this registration.
     */
    pr_reg->pr_res_holder = res_holder;

    list_add_tail(&pr_reg->pr_reg_aptpl_list, &pr_tmpl->aptpl_reg_list);
    pr_debug("SPC-3 PR APTPL Successfully added registration%s from"
            " metadata\n", (res_holder) ? "+reservation" : "");
    return 0;
}

static void core_scsi3_aptpl_reserve(
    struct se_device *dev,
    struct se_portal_group *tpg,
    struct se_node_acl *node_acl,
    struct t10_pr_registration *pr_reg)
{
    char i_buf[PR_REG_ISID_ID_LEN];
    int prf_isid;

    memset(i_buf, 0, PR_REG_ISID_ID_LEN);
    prf_isid = core_pr_dump_initiator_port(pr_reg, &i_buf[0],
                PR_REG_ISID_ID_LEN);

    spin_lock(&dev->dev_reservation_lock);
    dev->dev_pr_res_holder = pr_reg;
    spin_unlock(&dev->dev_reservation_lock);

    pr_debug("SPC-3 PR [%s] Service Action: APTPL RESERVE created"
        " new reservation holder TYPE: %s ALL_TG_PT: %d\n",
        tpg->se_tpg_tfo->get_fabric_name(),
        core_scsi3_pr_dump_type(pr_reg->pr_res_type),
        (pr_reg->pr_reg_all_tg_pt) ? 1 : 0);
    pr_debug("SPC-3 PR [%s] RESERVE Node: %s%s\n",
        tpg->se_tpg_tfo->get_fabric_name(), node_acl->initiatorname,
        (prf_isid) ? &i_buf[0] : "");
}

static void __core_scsi3_add_registration(struct se_device *, struct se_node_acl *,
                struct t10_pr_registration *, int, int);

static int __core_scsi3_check_aptpl_registration(
    struct se_device *dev,
    struct se_portal_group *tpg,
    struct se_lun *lun,
    u32 target_lun,
    struct se_node_acl *nacl,
    struct se_dev_entry *deve)
{
    struct t10_pr_registration *pr_reg, *pr_reg_tmp;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    unsigned char i_port[PR_APTPL_MAX_IPORT_LEN];
    unsigned char t_port[PR_APTPL_MAX_TPORT_LEN];
    u16 tpgt;

    memset(i_port, 0, PR_APTPL_MAX_IPORT_LEN);
    memset(t_port, 0, PR_APTPL_MAX_TPORT_LEN);
    /*
     * Copy Initiator Port information from struct se_node_acl
     */
    snprintf(i_port, PR_APTPL_MAX_IPORT_LEN, "%s", nacl->initiatorname);
    snprintf(t_port, PR_APTPL_MAX_TPORT_LEN, "%s",
            tpg->se_tpg_tfo->tpg_get_wwn(tpg));
    tpgt = tpg->se_tpg_tfo->tpg_get_tag(tpg);
    /*
     * Look for the matching registrations+reservation from those
     * created from APTPL metadata.  Note that multiple registrations
     * may exist for fabrics that use ISIDs in their SCSI Initiator Port
     * TransportIDs.
     */
    spin_lock(&pr_tmpl->aptpl_reg_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp, &pr_tmpl->aptpl_reg_list,
                pr_reg_aptpl_list) {
        if (!strcmp(pr_reg->pr_iport, i_port) &&
             (pr_reg->pr_res_mapped_lun == deve->mapped_lun) &&
            !(strcmp(pr_reg->pr_tport, t_port)) &&
             (pr_reg->pr_reg_tpgt == tpgt) &&
             (pr_reg->pr_aptpl_target_lun == target_lun)) {

            pr_reg->pr_reg_nacl = nacl;
            pr_reg->pr_reg_deve = deve;
            pr_reg->pr_reg_tg_pt_lun = lun;

            list_del(&pr_reg->pr_reg_aptpl_list);
            spin_unlock(&pr_tmpl->aptpl_reg_lock);
            /*
             * At this point all of the pointers in *pr_reg will
             * be setup, so go ahead and add the registration.
             */

            __core_scsi3_add_registration(dev, nacl, pr_reg, 0, 0);
            /*
             * If this registration is the reservation holder,
             * make that happen now..
             */
            if (pr_reg->pr_res_holder)
                core_scsi3_aptpl_reserve(dev, tpg,
                        nacl, pr_reg);
            /*
             * Reenable pr_aptpl_active to accept new metadata
             * updates once the SCSI device is active again..
             */
            spin_lock(&pr_tmpl->aptpl_reg_lock);
            pr_tmpl->pr_aptpl_active = 1;
        }
    }
    spin_unlock(&pr_tmpl->aptpl_reg_lock);

    return 0;
}

int core_scsi3_check_aptpl_registration(
    struct se_device *dev,
    struct se_portal_group *tpg,
    struct se_lun *lun,
    struct se_lun_acl *lun_acl)
{
    struct se_subsystem_dev *su_dev = dev->se_sub_dev;
    struct se_node_acl *nacl = lun_acl->se_lun_nacl;
    struct se_dev_entry *deve = nacl->device_list[lun_acl->mapped_lun];

    if (su_dev->t10_pr.res_type != SPC3_PERSISTENT_RESERVATIONS)
        return 0;

    return __core_scsi3_check_aptpl_registration(dev, tpg, lun,
                lun->unpacked_lun, nacl, deve);
}

static void __core_scsi3_dump_registration(
    struct target_core_fabric_ops *tfo,
    struct se_device *dev,
    struct se_node_acl *nacl,
    struct t10_pr_registration *pr_reg,
    int register_type)
{
    struct se_portal_group *se_tpg = nacl->se_tpg;
    char i_buf[PR_REG_ISID_ID_LEN];
    int prf_isid;

    memset(&i_buf[0], 0, PR_REG_ISID_ID_LEN);
    prf_isid = core_pr_dump_initiator_port(pr_reg, &i_buf[0],
                PR_REG_ISID_ID_LEN);

    pr_debug("SPC-3 PR [%s] Service Action: REGISTER%s Initiator"
        " Node: %s%s\n", tfo->get_fabric_name(), (register_type == 2) ?
        "_AND_MOVE" : (register_type == 1) ?
        "_AND_IGNORE_EXISTING_KEY" : "", nacl->initiatorname,
        (prf_isid) ? i_buf : "");
    pr_debug("SPC-3 PR [%s] registration on Target Port: %s,0x%04x\n",
         tfo->get_fabric_name(), tfo->tpg_get_wwn(se_tpg),
        tfo->tpg_get_tag(se_tpg));
    pr_debug("SPC-3 PR [%s] for %s TCM Subsystem %s Object Target"
        " Port(s)\n",  tfo->get_fabric_name(),
        (pr_reg->pr_reg_all_tg_pt) ? "ALL" : "SINGLE",
        dev->transport->name);
    pr_debug("SPC-3 PR [%s] SA Res Key: 0x%016Lx PRgeneration:"
        " 0x%08x  APTPL: %d\n", tfo->get_fabric_name(),
        pr_reg->pr_res_key, pr_reg->pr_res_generation,
        pr_reg->pr_reg_aptpl);
}

/*
 * this function can be called with struct se_device->dev_reservation_lock
 * when register_move = 1
 */
static void __core_scsi3_add_registration(
    struct se_device *dev,
    struct se_node_acl *nacl,
    struct t10_pr_registration *pr_reg,
    int register_type,
    int register_move)
{
    struct se_subsystem_dev *su_dev = dev->se_sub_dev;
    struct target_core_fabric_ops *tfo = nacl->se_tpg->se_tpg_tfo;
    struct t10_pr_registration *pr_reg_tmp, *pr_reg_tmp_safe;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;

    /*
     * Increment PRgeneration counter for struct se_device upon a successful
     * REGISTER, see spc4r17 section 6.3.2 READ_KEYS service action
     *
     * Also, when register_move = 1 for PROUT REGISTER_AND_MOVE service
     * action, the struct se_device->dev_reservation_lock will already be held,
     * so we do not call core_scsi3_pr_generation() which grabs the lock
     * for the REGISTER.
     */
    pr_reg->pr_res_generation = (register_move) ?
            su_dev->t10_pr.pr_generation++ :
            core_scsi3_pr_generation(dev);

    spin_lock(&pr_tmpl->registration_lock);
    list_add_tail(&pr_reg->pr_reg_list, &pr_tmpl->registration_list);
    pr_reg->pr_reg_deve->def_pr_registered = 1;

    __core_scsi3_dump_registration(tfo, dev, nacl, pr_reg, register_type);
    spin_unlock(&pr_tmpl->registration_lock);
    /*
     * Skip extra processing for ALL_TG_PT=0 or REGISTER_AND_MOVE.
     */
    if (!pr_reg->pr_reg_all_tg_pt || register_move)
        return;
    /*
     * Walk pr_reg->pr_reg_atp_list and add registrations for ALL_TG_PT=1
     * allocated in __core_scsi3_alloc_registration()
     */
    list_for_each_entry_safe(pr_reg_tmp, pr_reg_tmp_safe,
            &pr_reg->pr_reg_atp_list, pr_reg_atp_mem_list) {
        list_del(&pr_reg_tmp->pr_reg_atp_mem_list);

        pr_reg_tmp->pr_res_generation = core_scsi3_pr_generation(dev);

        spin_lock(&pr_tmpl->registration_lock);
        list_add_tail(&pr_reg_tmp->pr_reg_list,
                  &pr_tmpl->registration_list);
        pr_reg_tmp->pr_reg_deve->def_pr_registered = 1;

        __core_scsi3_dump_registration(tfo, dev,
                pr_reg_tmp->pr_reg_nacl, pr_reg_tmp,
                register_type);
        spin_unlock(&pr_tmpl->registration_lock);
        /*
         * Drop configfs group dependency reference from
         * __core_scsi3_alloc_registration()
         */
        core_scsi3_lunacl_undepend_item(pr_reg_tmp->pr_reg_deve);
    }
}

static int core_scsi3_alloc_registration(
    struct se_device *dev,
    struct se_node_acl *nacl,
    struct se_dev_entry *deve,
    unsigned char *isid,
    u64 sa_res_key,
    int all_tg_pt,
    int aptpl,
    int register_type,
    int register_move)
{
    struct t10_pr_registration *pr_reg;

    pr_reg = __core_scsi3_alloc_registration(dev, nacl, deve, isid,
            sa_res_key, all_tg_pt, aptpl);
    if (!pr_reg)
        return -EPERM;

    __core_scsi3_add_registration(dev, nacl, pr_reg,
            register_type, register_move);
    return 0;
}

static struct t10_pr_registration *__core_scsi3_locate_pr_reg(
    struct se_device *dev,
    struct se_node_acl *nacl,
    unsigned char *isid)
{
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    struct t10_pr_registration *pr_reg, *pr_reg_tmp;
    struct se_portal_group *tpg;

    spin_lock(&pr_tmpl->registration_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp,
            &pr_tmpl->registration_list, pr_reg_list) {
        /*
         * First look for a matching struct se_node_acl
         */
        if (pr_reg->pr_reg_nacl != nacl)
            continue;

        tpg = pr_reg->pr_reg_nacl->se_tpg;
        /*
         * If this registration does NOT contain a fabric provided
         * ISID, then we have found a match.
         */
        if (!pr_reg->isid_present_at_reg) {
            /*
             * Determine if this SCSI device server requires that
             * SCSI Intiatior TransportID w/ ISIDs is enforced
             * for fabric modules (iSCSI) requiring them.
             */
            if (tpg->se_tpg_tfo->sess_get_initiator_sid != NULL) {
                if (dev->se_sub_dev->se_dev_attrib.enforce_pr_isids)
                    continue;
            }
            atomic_inc(&pr_reg->pr_res_holders);
            smp_mb__after_atomic_inc();
            spin_unlock(&pr_tmpl->registration_lock);
            return pr_reg;
        }
        /*
         * If the *pr_reg contains a fabric defined ISID for multi-value
         * SCSI Initiator Port TransportIDs, then we expect a valid
         * matching ISID to be provided by the local SCSI Initiator Port.
         */
        if (!isid)
            continue;
        if (strcmp(isid, pr_reg->pr_reg_isid))
            continue;

        atomic_inc(&pr_reg->pr_res_holders);
        smp_mb__after_atomic_inc();
        spin_unlock(&pr_tmpl->registration_lock);
        return pr_reg;
    }
    spin_unlock(&pr_tmpl->registration_lock);

    return NULL;
}

static struct t10_pr_registration *core_scsi3_locate_pr_reg(
    struct se_device *dev,
    struct se_node_acl *nacl,
    struct se_session *sess)
{
    struct se_portal_group *tpg = nacl->se_tpg;
    unsigned char buf[PR_REG_ISID_LEN], *isid_ptr = NULL;

    if (tpg->se_tpg_tfo->sess_get_initiator_sid != NULL) {
        memset(&buf[0], 0, PR_REG_ISID_LEN);
        tpg->se_tpg_tfo->sess_get_initiator_sid(sess, &buf[0],
                    PR_REG_ISID_LEN);
        isid_ptr = &buf[0];
    }

    return __core_scsi3_locate_pr_reg(dev, nacl, isid_ptr);
}

static void core_scsi3_put_pr_reg(struct t10_pr_registration *pr_reg)
{
    atomic_dec(&pr_reg->pr_res_holders);
    smp_mb__after_atomic_dec();
}

static int core_scsi3_check_implict_release(
    struct se_device *dev,
    struct t10_pr_registration *pr_reg)
{
    struct se_node_acl *nacl = pr_reg->pr_reg_nacl;
    struct t10_pr_registration *pr_res_holder;
    int ret = 0;

    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if (!pr_res_holder) {
        spin_unlock(&dev->dev_reservation_lock);
        return ret;
    }
    if (pr_res_holder == pr_reg) {
        /*
         * Perform an implict RELEASE if the registration that
         * is being released is holding the reservation.
         *
         * From spc4r17, section 5.7.11.1:
         *
         * e) If the I_T nexus is the persistent reservation holder
         *    and the persistent reservation is not an all registrants
         *    type, then a PERSISTENT RESERVE OUT command with REGISTER
         *    service action or REGISTER AND  IGNORE EXISTING KEY
         *    service action with the SERVICE ACTION RESERVATION KEY
         *    field set to zero (see 5.7.11.3).
         */
        __core_scsi3_complete_pro_release(dev, nacl, pr_reg, 0);
        ret = 1;
        /*
         * For 'All Registrants' reservation types, all existing
         * registrations are still processed as reservation holders
         * in core_scsi3_pr_seq_non_holder() after the initial
         * reservation holder is implictly released here.
         */
    } else if (pr_reg->pr_reg_all_tg_pt &&
          (!strcmp(pr_res_holder->pr_reg_nacl->initiatorname,
              pr_reg->pr_reg_nacl->initiatorname)) &&
          (pr_res_holder->pr_res_key == pr_reg->pr_res_key)) {
        pr_err("SPC-3 PR: Unable to perform ALL_TG_PT=1"
            " UNREGISTER while existing reservation with matching"
            " key 0x%016Lx is present from another SCSI Initiator"
            " Port\n", pr_reg->pr_res_key);
        ret = -EPERM;
    }
    spin_unlock(&dev->dev_reservation_lock);

    return ret;
}

/*
 * Called with struct t10_reservation->registration_lock held.
 */
static void __core_scsi3_free_registration(
    struct se_device *dev,
    struct t10_pr_registration *pr_reg,
    struct list_head *preempt_and_abort_list,
    int dec_holders)
{
    struct target_core_fabric_ops *tfo =
            pr_reg->pr_reg_nacl->se_tpg->se_tpg_tfo;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    char i_buf[PR_REG_ISID_ID_LEN];
    int prf_isid;

    memset(i_buf, 0, PR_REG_ISID_ID_LEN);
    prf_isid = core_pr_dump_initiator_port(pr_reg, &i_buf[0],
                PR_REG_ISID_ID_LEN);

    pr_reg->pr_reg_deve->def_pr_registered = 0;
    pr_reg->pr_reg_deve->pr_res_key = 0;
    list_del(&pr_reg->pr_reg_list);
    /*
     * Caller accessing *pr_reg using core_scsi3_locate_pr_reg(),
     * so call core_scsi3_put_pr_reg() to decrement our reference.
     */
    if (dec_holders)
        core_scsi3_put_pr_reg(pr_reg);
    /*
     * Wait until all reference from any other I_T nexuses for this
     * *pr_reg have been released.  Because list_del() is called above,
     * the last core_scsi3_put_pr_reg(pr_reg) will release this reference
     * count back to zero, and we release *pr_reg.
     */
    while (atomic_read(&pr_reg->pr_res_holders) != 0) {
        spin_unlock(&pr_tmpl->registration_lock);
        pr_debug("SPC-3 PR [%s] waiting for pr_res_holders\n",
                tfo->get_fabric_name());
        cpu_relax();
        spin_lock(&pr_tmpl->registration_lock);
    }

    pr_debug("SPC-3 PR [%s] Service Action: UNREGISTER Initiator"
        " Node: %s%s\n", tfo->get_fabric_name(),
        pr_reg->pr_reg_nacl->initiatorname,
        (prf_isid) ? &i_buf[0] : "");
    pr_debug("SPC-3 PR [%s] for %s TCM Subsystem %s Object Target"
        " Port(s)\n", tfo->get_fabric_name(),
        (pr_reg->pr_reg_all_tg_pt) ? "ALL" : "SINGLE",
        dev->transport->name);
    pr_debug("SPC-3 PR [%s] SA Res Key: 0x%016Lx PRgeneration:"
        " 0x%08x\n", tfo->get_fabric_name(), pr_reg->pr_res_key,
        pr_reg->pr_res_generation);

    if (!preempt_and_abort_list) {
        pr_reg->pr_reg_deve = NULL;
        pr_reg->pr_reg_nacl = NULL;
        kfree(pr_reg->pr_aptpl_buf);
        kmem_cache_free(t10_pr_reg_cache, pr_reg);
        return;
    }
    /*
     * For PREEMPT_AND_ABORT, the list of *pr_reg in preempt_and_abort_list
     * are released once the ABORT_TASK_SET has completed..
     */
    list_add_tail(&pr_reg->pr_reg_abort_list, preempt_and_abort_list);
}

void core_scsi3_free_pr_reg_from_nacl(
    struct se_device *dev,
    struct se_node_acl *nacl)
{
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    struct t10_pr_registration *pr_reg, *pr_reg_tmp, *pr_res_holder;
    /*
     * If the passed se_node_acl matches the reservation holder,
     * release the reservation.
     */
    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if ((pr_res_holder != NULL) &&
        (pr_res_holder->pr_reg_nacl == nacl))
        __core_scsi3_complete_pro_release(dev, nacl, pr_res_holder, 0);
    spin_unlock(&dev->dev_reservation_lock);
    /*
     * Release any registration associated with the struct se_node_acl.
     */
    spin_lock(&pr_tmpl->registration_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp,
            &pr_tmpl->registration_list, pr_reg_list) {

        if (pr_reg->pr_reg_nacl != nacl)
            continue;

        __core_scsi3_free_registration(dev, pr_reg, NULL, 0);
    }
    spin_unlock(&pr_tmpl->registration_lock);
}

void core_scsi3_free_all_registrations(
    struct se_device *dev)
{
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    struct t10_pr_registration *pr_reg, *pr_reg_tmp, *pr_res_holder;

    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if (pr_res_holder != NULL) {
        struct se_node_acl *pr_res_nacl = pr_res_holder->pr_reg_nacl;
        __core_scsi3_complete_pro_release(dev, pr_res_nacl,
                pr_res_holder, 0);
    }
    spin_unlock(&dev->dev_reservation_lock);

    spin_lock(&pr_tmpl->registration_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp,
            &pr_tmpl->registration_list, pr_reg_list) {

        __core_scsi3_free_registration(dev, pr_reg, NULL, 0);
    }
    spin_unlock(&pr_tmpl->registration_lock);

    spin_lock(&pr_tmpl->aptpl_reg_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp, &pr_tmpl->aptpl_reg_list,
                pr_reg_aptpl_list) {
        list_del(&pr_reg->pr_reg_aptpl_list);
        kfree(pr_reg->pr_aptpl_buf);
        kmem_cache_free(t10_pr_reg_cache, pr_reg);
    }
    spin_unlock(&pr_tmpl->aptpl_reg_lock);
}

static int core_scsi3_tpg_depend_item(struct se_portal_group *tpg)
{
    return configfs_depend_item(tpg->se_tpg_tfo->tf_subsys,
            &tpg->tpg_group.cg_item);
}

static void core_scsi3_tpg_undepend_item(struct se_portal_group *tpg)
{
    configfs_undepend_item(tpg->se_tpg_tfo->tf_subsys,
            &tpg->tpg_group.cg_item);

    atomic_dec(&tpg->tpg_pr_ref_count);
    smp_mb__after_atomic_dec();
}

static int core_scsi3_nodeacl_depend_item(struct se_node_acl *nacl)
{
    struct se_portal_group *tpg = nacl->se_tpg;

    if (nacl->dynamic_node_acl)
        return 0;

    return configfs_depend_item(tpg->se_tpg_tfo->tf_subsys,
            &nacl->acl_group.cg_item);
}

static void core_scsi3_nodeacl_undepend_item(struct se_node_acl *nacl)
{
    struct se_portal_group *tpg = nacl->se_tpg;

    if (nacl->dynamic_node_acl) {
        atomic_dec(&nacl->acl_pr_ref_count);
        smp_mb__after_atomic_dec();
        return;
    }

    configfs_undepend_item(tpg->se_tpg_tfo->tf_subsys,
            &nacl->acl_group.cg_item);

    atomic_dec(&nacl->acl_pr_ref_count);
    smp_mb__after_atomic_dec();
}

static int core_scsi3_lunacl_depend_item(struct se_dev_entry *se_deve)
{
    struct se_lun_acl *lun_acl = se_deve->se_lun_acl;
    struct se_node_acl *nacl;
    struct se_portal_group *tpg;
    /*
     * For nacl->dynamic_node_acl=1
     */
    if (!lun_acl)
        return 0;

    nacl = lun_acl->se_lun_nacl;
    tpg = nacl->se_tpg;

    return configfs_depend_item(tpg->se_tpg_tfo->tf_subsys,
            &lun_acl->se_lun_group.cg_item);
}

static void core_scsi3_lunacl_undepend_item(struct se_dev_entry *se_deve)
{
    struct se_lun_acl *lun_acl = se_deve->se_lun_acl;
    struct se_node_acl *nacl;
    struct se_portal_group *tpg;
    /*
     * For nacl->dynamic_node_acl=1
     */
    if (!lun_acl) {
        atomic_dec(&se_deve->pr_ref_count);
        smp_mb__after_atomic_dec();
        return;
    }
    nacl = lun_acl->se_lun_nacl;
    tpg = nacl->se_tpg;

    configfs_undepend_item(tpg->se_tpg_tfo->tf_subsys,
            &lun_acl->se_lun_group.cg_item);

    atomic_dec(&se_deve->pr_ref_count);
    smp_mb__after_atomic_dec();
}

static int core_scsi3_decode_spec_i_port(
    struct se_cmd *cmd,
    struct se_portal_group *tpg,
    unsigned char *l_isid,
    u64 sa_res_key,
    int all_tg_pt,
    int aptpl)
{
    struct se_device *dev = cmd->se_dev;
    struct se_port *tmp_port;
    struct se_portal_group *dest_tpg = NULL, *tmp_tpg;
    struct se_session *se_sess = cmd->se_sess;
    struct se_node_acl *dest_node_acl = NULL;
    struct se_dev_entry *dest_se_deve = NULL, *local_se_deve;
    struct t10_pr_registration *dest_pr_reg, *local_pr_reg, *pr_reg_e;
    struct t10_pr_registration *pr_reg_tmp, *pr_reg_tmp_safe;
    LIST_HEAD(tid_dest_list);
    struct pr_transport_id_holder *tidh_new, *tidh, *tidh_tmp;
    struct target_core_fabric_ops *tmp_tf_ops;
    unsigned char *buf;
    unsigned char *ptr, *i_str = NULL, proto_ident, tmp_proto_ident;
    char *iport_ptr = NULL, dest_iport[64], i_buf[PR_REG_ISID_ID_LEN];
    u32 tpdl, tid_len = 0;
    int ret, dest_local_nexus, prf_isid;
    u32 dest_rtpi = 0;

    memset(dest_iport, 0, 64);

    local_se_deve = se_sess->se_node_acl->device_list[cmd->orig_fe_lun];
    /*
     * Allocate a struct pr_transport_id_holder and setup the
     * local_node_acl and local_se_deve pointers and add to
     * struct list_head tid_dest_list for add registration
     * processing in the loop of tid_dest_list below.
     */
    tidh_new = kzalloc(sizeof(struct pr_transport_id_holder), GFP_KERNEL);
    if (!tidh_new) {
        pr_err("Unable to allocate tidh_new\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    INIT_LIST_HEAD(&tidh_new->dest_list);
    tidh_new->dest_tpg = tpg;
    tidh_new->dest_node_acl = se_sess->se_node_acl;
    tidh_new->dest_se_deve = local_se_deve;

    local_pr_reg = __core_scsi3_alloc_registration(cmd->se_dev,
                se_sess->se_node_acl, local_se_deve, l_isid,
                sa_res_key, all_tg_pt, aptpl);
    if (!local_pr_reg) {
        kfree(tidh_new);
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -ENOMEM;
    }
    tidh_new->dest_pr_reg = local_pr_reg;
    /*
     * The local I_T nexus does not hold any configfs dependances,
     * so we set tid_h->dest_local_nexus=1 to prevent the
     * configfs_undepend_item() calls in the tid_dest_list loops below.
     */
    tidh_new->dest_local_nexus = 1;
    list_add_tail(&tidh_new->dest_list, &tid_dest_list);

    if (cmd->data_length < 28) {
        pr_warn("SPC-PR: Received PR OUT parameter list"
            " length too small: %u\n", cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }

    buf = transport_kmap_data_sg(cmd);
    /*
     * For a PERSISTENT RESERVE OUT specify initiator ports payload,
     * first extract TransportID Parameter Data Length, and make sure
     * the value matches up to the SCSI expected data transfer length.
     */
    tpdl = (buf[24] & 0xff) << 24;
    tpdl |= (buf[25] & 0xff) << 16;
    tpdl |= (buf[26] & 0xff) << 8;
    tpdl |= buf[27] & 0xff;

    if ((tpdl + 28) != cmd->data_length) {
        pr_err("SPC-3 PR: Illegal tpdl: %u + 28 byte header"
            " does not equal CDB data_length: %u\n", tpdl,
            cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }
    /*
     * Start processing the received transport IDs using the
     * receiving I_T Nexus portal's fabric dependent methods to
     * obtain the SCSI Initiator Port/Device Identifiers.
     */
    ptr = &buf[28];

    while (tpdl > 0) {
        proto_ident = (ptr[0] & 0x0f);
        dest_tpg = NULL;

        spin_lock(&dev->se_port_lock);
        list_for_each_entry(tmp_port, &dev->dev_sep_list, sep_list) {
            tmp_tpg = tmp_port->sep_tpg;
            if (!tmp_tpg)
                continue;
            tmp_tf_ops = tmp_tpg->se_tpg_tfo;
            if (!tmp_tf_ops)
                continue;
            if (!tmp_tf_ops->get_fabric_proto_ident ||
                !tmp_tf_ops->tpg_parse_pr_out_transport_id)
                continue;
            /*
             * Look for the matching proto_ident provided by
             * the received TransportID
             */
            tmp_proto_ident = tmp_tf_ops->get_fabric_proto_ident(tmp_tpg);
            if (tmp_proto_ident != proto_ident)
                continue;
            dest_rtpi = tmp_port->sep_rtpi;

            i_str = tmp_tf_ops->tpg_parse_pr_out_transport_id(
                    tmp_tpg, (const char *)ptr, &tid_len,
                    &iport_ptr);
            if (!i_str)
                continue;

            atomic_inc(&tmp_tpg->tpg_pr_ref_count);
            smp_mb__after_atomic_inc();
            spin_unlock(&dev->se_port_lock);

            ret = core_scsi3_tpg_depend_item(tmp_tpg);
            if (ret != 0) {
                pr_err(" core_scsi3_tpg_depend_item()"
                    " for tmp_tpg\n");
                atomic_dec(&tmp_tpg->tpg_pr_ref_count);
                smp_mb__after_atomic_dec();
                cmd->scsi_sense_reason =
                    TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                ret = -EINVAL;
                goto out;
            }
            /*
             * Locate the destination initiator ACL to be registered
             * from the decoded fabric module specific TransportID
             * at *i_str.
             */
            spin_lock_irq(&tmp_tpg->acl_node_lock);
            dest_node_acl = __core_tpg_get_initiator_node_acl(
                        tmp_tpg, i_str);
            if (dest_node_acl) {
                atomic_inc(&dest_node_acl->acl_pr_ref_count);
                smp_mb__after_atomic_inc();
            }
            spin_unlock_irq(&tmp_tpg->acl_node_lock);

            if (!dest_node_acl) {
                core_scsi3_tpg_undepend_item(tmp_tpg);
                spin_lock(&dev->se_port_lock);
                continue;
            }

            ret = core_scsi3_nodeacl_depend_item(dest_node_acl);
            if (ret != 0) {
                pr_err("configfs_depend_item() failed"
                    " for dest_node_acl->acl_group\n");
                atomic_dec(&dest_node_acl->acl_pr_ref_count);
                smp_mb__after_atomic_dec();
                core_scsi3_tpg_undepend_item(tmp_tpg);
                cmd->scsi_sense_reason =
                    TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                ret = -EINVAL;
                goto out;
            }

            dest_tpg = tmp_tpg;
            pr_debug("SPC-3 PR SPEC_I_PT: Located %s Node:"
                " %s Port RTPI: %hu\n",
                dest_tpg->se_tpg_tfo->get_fabric_name(),
                dest_node_acl->initiatorname, dest_rtpi);

            spin_lock(&dev->se_port_lock);
            break;
        }
        spin_unlock(&dev->se_port_lock);

        if (!dest_tpg) {
            pr_err("SPC-3 PR SPEC_I_PT: Unable to locate"
                    " dest_tpg\n");
            cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
            ret = -EINVAL;
            goto out;
        }

        pr_debug("SPC-3 PR SPEC_I_PT: Got %s data_length: %u tpdl: %u"
            " tid_len: %d for %s + %s\n",
            dest_tpg->se_tpg_tfo->get_fabric_name(), cmd->data_length,
            tpdl, tid_len, i_str, iport_ptr);

        if (tid_len > tpdl) {
            pr_err("SPC-3 PR SPEC_I_PT: Illegal tid_len:"
                " %u for Transport ID: %s\n", tid_len, ptr);
            core_scsi3_nodeacl_undepend_item(dest_node_acl);
            core_scsi3_tpg_undepend_item(dest_tpg);
            cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
            ret = -EINVAL;
            goto out;
        }
        /*
         * Locate the desintation struct se_dev_entry pointer for matching
         * RELATIVE TARGET PORT IDENTIFIER on the receiving I_T Nexus
         * Target Port.
         */
        dest_se_deve = core_get_se_deve_from_rtpi(dest_node_acl,
                    dest_rtpi);
        if (!dest_se_deve) {
            pr_err("Unable to locate %s dest_se_deve"
                " from destination RTPI: %hu\n",
                dest_tpg->se_tpg_tfo->get_fabric_name(),
                dest_rtpi);

            core_scsi3_nodeacl_undepend_item(dest_node_acl);
            core_scsi3_tpg_undepend_item(dest_tpg);
            cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
            ret = -EINVAL;
            goto out;
        }

        ret = core_scsi3_lunacl_depend_item(dest_se_deve);
        if (ret < 0) {
            pr_err("core_scsi3_lunacl_depend_item()"
                    " failed\n");
            atomic_dec(&dest_se_deve->pr_ref_count);
            smp_mb__after_atomic_dec();
            core_scsi3_nodeacl_undepend_item(dest_node_acl);
            core_scsi3_tpg_undepend_item(dest_tpg);
            cmd->scsi_sense_reason =
                TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
            ret = -EINVAL;
            goto out;
        }

        pr_debug("SPC-3 PR SPEC_I_PT: Located %s Node: %s"
            " dest_se_deve mapped_lun: %u\n",
            dest_tpg->se_tpg_tfo->get_fabric_name(),
            dest_node_acl->initiatorname, dest_se_deve->mapped_lun);

        /*
         * Skip any TransportIDs that already have a registration for
         * this target port.
         */
        pr_reg_e = __core_scsi3_locate_pr_reg(dev, dest_node_acl,
                    iport_ptr);
        if (pr_reg_e) {
            core_scsi3_put_pr_reg(pr_reg_e);
            core_scsi3_lunacl_undepend_item(dest_se_deve);
            core_scsi3_nodeacl_undepend_item(dest_node_acl);
            core_scsi3_tpg_undepend_item(dest_tpg);
            ptr += tid_len;
            tpdl -= tid_len;
            tid_len = 0;
            continue;
        }
        /*
         * Allocate a struct pr_transport_id_holder and setup
         * the dest_node_acl and dest_se_deve pointers for the
         * loop below.
         */
        tidh_new = kzalloc(sizeof(struct pr_transport_id_holder),
                GFP_KERNEL);
        if (!tidh_new) {
            pr_err("Unable to allocate tidh_new\n");
            core_scsi3_lunacl_undepend_item(dest_se_deve);
            core_scsi3_nodeacl_undepend_item(dest_node_acl);
            core_scsi3_tpg_undepend_item(dest_tpg);
            cmd->scsi_sense_reason =
                TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
            ret = -ENOMEM;
            goto out;
        }
        INIT_LIST_HEAD(&tidh_new->dest_list);
        tidh_new->dest_tpg = dest_tpg;
        tidh_new->dest_node_acl = dest_node_acl;
        tidh_new->dest_se_deve = dest_se_deve;

        /*
         * Allocate, but do NOT add the registration for the
         * TransportID referenced SCSI Initiator port.  This
         * done because of the following from spc4r17 in section
         * 6.14.3 wrt SPEC_I_PT:
         *
         * "If a registration fails for any initiator port (e.g., if th
         * logical unit does not have enough resources available to
         * hold the registration information), no registrations shall be
         * made, and the command shall be terminated with
         * CHECK CONDITION status."
         *
         * That means we call __core_scsi3_alloc_registration() here,
         * and then call __core_scsi3_add_registration() in the
         * 2nd loop which will never fail.
         */
        dest_pr_reg = __core_scsi3_alloc_registration(cmd->se_dev,
                dest_node_acl, dest_se_deve, iport_ptr,
                sa_res_key, all_tg_pt, aptpl);
        if (!dest_pr_reg) {
            core_scsi3_lunacl_undepend_item(dest_se_deve);
            core_scsi3_nodeacl_undepend_item(dest_node_acl);
            core_scsi3_tpg_undepend_item(dest_tpg);
            kfree(tidh_new);
            cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
            ret = -EINVAL;
            goto out;
        }
        tidh_new->dest_pr_reg = dest_pr_reg;
        list_add_tail(&tidh_new->dest_list, &tid_dest_list);

        ptr += tid_len;
        tpdl -= tid_len;
        tid_len = 0;

    }

    transport_kunmap_data_sg(cmd);

    /*
     * Go ahead and create a registrations from tid_dest_list for the
     * SPEC_I_PT provided TransportID for the *tidh referenced dest_node_acl
     * and dest_se_deve.
     *
     * The SA Reservation Key from the PROUT is set for the
     * registration, and ALL_TG_PT is also passed.  ALL_TG_PT=1
     * means that the TransportID Initiator port will be
     * registered on all of the target ports in the SCSI target device
     * ALL_TG_PT=0 means the registration will only be for the
     * SCSI target port the PROUT REGISTER with SPEC_I_PT=1
     * was received.
     */
    list_for_each_entry_safe(tidh, tidh_tmp, &tid_dest_list, dest_list) {
        dest_tpg = tidh->dest_tpg;
        dest_node_acl = tidh->dest_node_acl;
        dest_se_deve = tidh->dest_se_deve;
        dest_pr_reg = tidh->dest_pr_reg;
        dest_local_nexus = tidh->dest_local_nexus;

        list_del(&tidh->dest_list);
        kfree(tidh);

        memset(i_buf, 0, PR_REG_ISID_ID_LEN);
        prf_isid = core_pr_dump_initiator_port(dest_pr_reg, &i_buf[0],
                        PR_REG_ISID_ID_LEN);

        __core_scsi3_add_registration(cmd->se_dev, dest_node_acl,
                    dest_pr_reg, 0, 0);

        pr_debug("SPC-3 PR [%s] SPEC_I_PT: Successfully"
            " registered Transport ID for Node: %s%s Mapped LUN:"
            " %u\n", dest_tpg->se_tpg_tfo->get_fabric_name(),
            dest_node_acl->initiatorname, (prf_isid) ?
            &i_buf[0] : "", dest_se_deve->mapped_lun);

        if (dest_local_nexus)
            continue;

        core_scsi3_lunacl_undepend_item(dest_se_deve);
        core_scsi3_nodeacl_undepend_item(dest_node_acl);
        core_scsi3_tpg_undepend_item(dest_tpg);
    }

    return 0;
out:
    transport_kunmap_data_sg(cmd);
    /*
     * For the failure case, release everything from tid_dest_list
     * including *dest_pr_reg and the configfs dependances..
     */
    list_for_each_entry_safe(tidh, tidh_tmp, &tid_dest_list, dest_list) {
        dest_tpg = tidh->dest_tpg;
        dest_node_acl = tidh->dest_node_acl;
        dest_se_deve = tidh->dest_se_deve;
        dest_pr_reg = tidh->dest_pr_reg;
        dest_local_nexus = tidh->dest_local_nexus;

        list_del(&tidh->dest_list);
        kfree(tidh);
        /*
         * Release any extra ALL_TG_PT=1 registrations for
         * the SPEC_I_PT=1 case.
         */
        list_for_each_entry_safe(pr_reg_tmp, pr_reg_tmp_safe,
                &dest_pr_reg->pr_reg_atp_list,
                pr_reg_atp_mem_list) {
            list_del(&pr_reg_tmp->pr_reg_atp_mem_list);
            core_scsi3_lunacl_undepend_item(pr_reg_tmp->pr_reg_deve);
            kmem_cache_free(t10_pr_reg_cache, pr_reg_tmp);
        }

        kfree(dest_pr_reg->pr_aptpl_buf);
        kmem_cache_free(t10_pr_reg_cache, dest_pr_reg);

        if (dest_local_nexus)
            continue;

        core_scsi3_lunacl_undepend_item(dest_se_deve);
        core_scsi3_nodeacl_undepend_item(dest_node_acl);
        core_scsi3_tpg_undepend_item(dest_tpg);
    }
    return ret;
}

/*
 * Called with struct se_device->dev_reservation_lock held
 */
static int __core_scsi3_update_aptpl_buf(
    struct se_device *dev,
    unsigned char *buf,
    u32 pr_aptpl_buf_len,
    int clear_aptpl_metadata)
{
    struct se_lun *lun;
    struct se_portal_group *tpg;
    struct se_subsystem_dev *su_dev = dev->se_sub_dev;
    struct t10_pr_registration *pr_reg;
    unsigned char tmp[512], isid_buf[32];
    ssize_t len = 0;
    int reg_count = 0;

    memset(buf, 0, pr_aptpl_buf_len);
    /*
     * Called to clear metadata once APTPL has been deactivated.
     */
    if (clear_aptpl_metadata) {
        snprintf(buf, pr_aptpl_buf_len,
                "No Registrations or Reservations\n");
        return 0;
    }
    /*
     * Walk the registration list..
     */
    spin_lock(&su_dev->t10_pr.registration_lock);
    list_for_each_entry(pr_reg, &su_dev->t10_pr.registration_list,
            pr_reg_list) {

        tmp[0] = '\0';
        isid_buf[0] = '\0';
        tpg = pr_reg->pr_reg_nacl->se_tpg;
        lun = pr_reg->pr_reg_tg_pt_lun;
        /*
         * Write out any ISID value to APTPL metadata that was included
         * in the original registration.
         */
        if (pr_reg->isid_present_at_reg)
            snprintf(isid_buf, 32, "initiator_sid=%s\n",
                    pr_reg->pr_reg_isid);
        /*
         * Include special metadata if the pr_reg matches the
         * reservation holder.
         */
        if (dev->dev_pr_res_holder == pr_reg) {
            snprintf(tmp, 512, "PR_REG_START: %d"
                "\ninitiator_fabric=%s\n"
                "initiator_node=%s\n%s"
                "sa_res_key=%llu\n"
                "res_holder=1\nres_type=%02x\n"
                "res_scope=%02x\nres_all_tg_pt=%d\n"
                "mapped_lun=%u\n", reg_count,
                tpg->se_tpg_tfo->get_fabric_name(),
                pr_reg->pr_reg_nacl->initiatorname, isid_buf,
                pr_reg->pr_res_key, pr_reg->pr_res_type,
                pr_reg->pr_res_scope, pr_reg->pr_reg_all_tg_pt,
                pr_reg->pr_res_mapped_lun);
        } else {
            snprintf(tmp, 512, "PR_REG_START: %d\n"
                "initiator_fabric=%s\ninitiator_node=%s\n%s"
                "sa_res_key=%llu\nres_holder=0\n"
                "res_all_tg_pt=%d\nmapped_lun=%u\n",
                reg_count, tpg->se_tpg_tfo->get_fabric_name(),
                pr_reg->pr_reg_nacl->initiatorname, isid_buf,
                pr_reg->pr_res_key, pr_reg->pr_reg_all_tg_pt,
                pr_reg->pr_res_mapped_lun);
        }

        if ((len + strlen(tmp) >= pr_aptpl_buf_len)) {
            pr_err("Unable to update renaming"
                " APTPL metadata\n");
            spin_unlock(&su_dev->t10_pr.registration_lock);
            return -EMSGSIZE;
        }
        len += sprintf(buf+len, "%s", tmp);

        /*
         * Include information about the associated SCSI target port.
         */
        snprintf(tmp, 512, "target_fabric=%s\ntarget_node=%s\n"
            "tpgt=%hu\nport_rtpi=%hu\ntarget_lun=%u\nPR_REG_END:"
            " %d\n", tpg->se_tpg_tfo->get_fabric_name(),
            tpg->se_tpg_tfo->tpg_get_wwn(tpg),
            tpg->se_tpg_tfo->tpg_get_tag(tpg),
            lun->lun_sep->sep_rtpi, lun->unpacked_lun, reg_count);

        if ((len + strlen(tmp) >= pr_aptpl_buf_len)) {
            pr_err("Unable to update renaming"
                " APTPL metadata\n");
            spin_unlock(&su_dev->t10_pr.registration_lock);
            return -EMSGSIZE;
        }
        len += sprintf(buf+len, "%s", tmp);
        reg_count++;
    }
    spin_unlock(&su_dev->t10_pr.registration_lock);

    if (!reg_count)
        len += sprintf(buf+len, "No Registrations or Reservations");

    return 0;
}

static int core_scsi3_update_aptpl_buf(
    struct se_device *dev,
    unsigned char *buf,
    u32 pr_aptpl_buf_len,
    int clear_aptpl_metadata)
{
    int ret;

    spin_lock(&dev->dev_reservation_lock);
    ret = __core_scsi3_update_aptpl_buf(dev, buf, pr_aptpl_buf_len,
                clear_aptpl_metadata);
    spin_unlock(&dev->dev_reservation_lock);

    return ret;
}

/*
 * Called with struct se_device->aptpl_file_mutex held
 */
static int __core_scsi3_write_aptpl_to_file(
    struct se_device *dev,
    unsigned char *buf,
    u32 pr_aptpl_buf_len)
{
    struct t10_wwn *wwn = &dev->se_sub_dev->t10_wwn;
    struct file *file;
    struct iovec iov[1];
    mm_segment_t old_fs;
    int flags = O_RDWR | O_CREAT | O_TRUNC;
    char path[512];
    int ret;

    memset(iov, 0, sizeof(struct iovec));
    memset(path, 0, 512);

    if (strlen(&wwn->unit_serial[0]) >= 512) {
        pr_err("WWN value for struct se_device does not fit"
            " into path buffer\n");
        return -EMSGSIZE;
    }

    snprintf(path, 512, "/var/target/pr/aptpl_%s", &wwn->unit_serial[0]);
    file = filp_open(path, flags, 0600);
    if (IS_ERR(file) || !file || !file->f_dentry) {
        pr_err("filp_open(%s) for APTPL metadata"
            " failed\n", path);
        return IS_ERR(file) ? PTR_ERR(file) : -ENOENT;
    }

    iov[0].iov_base = &buf[0];
    if (!pr_aptpl_buf_len)
        iov[0].iov_len = (strlen(&buf[0]) + 1); /* Add extra for NULL */
    else
        iov[0].iov_len = pr_aptpl_buf_len;

    old_fs = get_fs();
    set_fs(get_ds());
    ret = vfs_writev(file, &iov[0], 1, &file->f_pos);
    set_fs(old_fs);

    if (ret < 0) {
        pr_debug("Error writing APTPL metadata file: %s\n", path);
        filp_close(file, NULL);
        return -EIO;
    }
    filp_close(file, NULL);

    return 0;
}

static int core_scsi3_update_and_write_aptpl(
    struct se_device *dev,
    unsigned char *in_buf,
    u32 in_pr_aptpl_buf_len)
{
    unsigned char null_buf[64], *buf;
    u32 pr_aptpl_buf_len;
    int ret, clear_aptpl_metadata = 0;
    /*
     * Can be called with a NULL pointer from PROUT service action CLEAR
     */
    if (!in_buf) {
        memset(null_buf, 0, 64);
        buf = &null_buf[0];
        /*
         * This will clear the APTPL metadata to:
         * "No Registrations or Reservations" status
         */
        pr_aptpl_buf_len = 64;
        clear_aptpl_metadata = 1;
    } else {
        buf = in_buf;
        pr_aptpl_buf_len = in_pr_aptpl_buf_len;
    }

    ret = core_scsi3_update_aptpl_buf(dev, buf, pr_aptpl_buf_len,
                clear_aptpl_metadata);
    if (ret != 0)
        return ret;
    /*
     * __core_scsi3_write_aptpl_to_file() will call strlen()
     * on the passed buf to determine pr_aptpl_buf_len.
     */
    ret = __core_scsi3_write_aptpl_to_file(dev, buf, 0);
    if (ret != 0)
        return ret;

    return ret;
}

static int core_scsi3_emulate_pro_register(
    struct se_cmd *cmd,
    u64 res_key,
    u64 sa_res_key,
    int aptpl,
    int all_tg_pt,
    int spec_i_pt,
    int ignore_key)
{
    struct se_session *se_sess = cmd->se_sess;
    struct se_device *dev = cmd->se_dev;
    struct se_dev_entry *se_deve;
    struct se_lun *se_lun = cmd->se_lun;
    struct se_portal_group *se_tpg;
    struct t10_pr_registration *pr_reg, *pr_reg_p, *pr_reg_tmp, *pr_reg_e;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    /* Used for APTPL metadata w/ UNREGISTER */
    unsigned char *pr_aptpl_buf = NULL;
    unsigned char isid_buf[PR_REG_ISID_LEN], *isid_ptr = NULL;
    int pr_holder = 0, ret = 0, type;

    if (!se_sess || !se_lun) {
        pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    se_tpg = se_sess->se_tpg;
    se_deve = se_sess->se_node_acl->device_list[cmd->orig_fe_lun];

    if (se_tpg->se_tpg_tfo->sess_get_initiator_sid) {
        memset(&isid_buf[0], 0, PR_REG_ISID_LEN);
        se_tpg->se_tpg_tfo->sess_get_initiator_sid(se_sess, &isid_buf[0],
                PR_REG_ISID_LEN);
        isid_ptr = &isid_buf[0];
    }
    /*
     * Follow logic from spc4r17 Section 5.7.7, Register Behaviors Table 47
     */
    pr_reg_e = core_scsi3_locate_pr_reg(dev, se_sess->se_node_acl, se_sess);
    if (!pr_reg_e) {
        if (res_key) {
            pr_warn("SPC-3 PR: Reservation Key non-zero"
                " for SA REGISTER, returning CONFLICT\n");
            cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
            return -EINVAL;
        }
        /*
         * Do nothing but return GOOD status.
         */
        if (!sa_res_key)
            return 0;

        if (!spec_i_pt) {
            /*
             * Perform the Service Action REGISTER on the Initiator
             * Port Endpoint that the PRO was received from on the
             * Logical Unit of the SCSI device server.
             */
            ret = core_scsi3_alloc_registration(cmd->se_dev,
                    se_sess->se_node_acl, se_deve, isid_ptr,
                    sa_res_key, all_tg_pt, aptpl,
                    ignore_key, 0);
            if (ret != 0) {
                pr_err("Unable to allocate"
                    " struct t10_pr_registration\n");
                cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
                return -EINVAL;
            }
        } else {
            /*
             * Register both the Initiator port that received
             * PROUT SA REGISTER + SPEC_I_PT=1 and extract SCSI
             * TransportID from Parameter list and loop through
             * fabric dependent parameter list while calling
             * logic from of core_scsi3_alloc_registration() for
             * each TransportID provided SCSI Initiator Port/Device
             */
            ret = core_scsi3_decode_spec_i_port(cmd, se_tpg,
                    isid_ptr, sa_res_key, all_tg_pt, aptpl);
            if (ret != 0)
                return ret;
        }
        /*
         * Nothing left to do for the APTPL=0 case.
         */
        if (!aptpl) {
            pr_tmpl->pr_aptpl_active = 0;
            core_scsi3_update_and_write_aptpl(cmd->se_dev, NULL, 0);
            pr_debug("SPC-3 PR: Set APTPL Bit Deactivated for"
                    " REGISTER\n");
            return 0;
        }
        /*
         * Locate the newly allocated local I_T Nexus *pr_reg, and
         * update the APTPL metadata information using its
         * preallocated *pr_reg->pr_aptpl_buf.
         */
        pr_reg = core_scsi3_locate_pr_reg(cmd->se_dev,
                se_sess->se_node_acl, se_sess);

        ret = core_scsi3_update_and_write_aptpl(cmd->se_dev,
                &pr_reg->pr_aptpl_buf[0],
                pr_tmpl->pr_aptpl_buf_len);
        if (!ret) {
            pr_tmpl->pr_aptpl_active = 1;
            pr_debug("SPC-3 PR: Set APTPL Bit Activated for REGISTER\n");
        }

        core_scsi3_put_pr_reg(pr_reg);
        return ret;
    } else {
        /*
         * Locate the existing *pr_reg via struct se_node_acl pointers
         */
        pr_reg = pr_reg_e;
        type = pr_reg->pr_res_type;

        if (!ignore_key) {
            if (res_key != pr_reg->pr_res_key) {
                pr_err("SPC-3 PR REGISTER: Received"
                    " res_key: 0x%016Lx does not match"
                    " existing SA REGISTER res_key:"
                    " 0x%016Lx\n", res_key,
                    pr_reg->pr_res_key);
                core_scsi3_put_pr_reg(pr_reg);
                cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
                return -EINVAL;
            }
        }
        if (spec_i_pt) {
            pr_err("SPC-3 PR UNREGISTER: SPEC_I_PT"
                " set while sa_res_key=0\n");
            core_scsi3_put_pr_reg(pr_reg);
            cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
            return -EINVAL;
        }
        /*
         * An existing ALL_TG_PT=1 registration being released
         * must also set ALL_TG_PT=1 in the incoming PROUT.
         */
        if (pr_reg->pr_reg_all_tg_pt && !(all_tg_pt)) {
            pr_err("SPC-3 PR UNREGISTER: ALL_TG_PT=1"
                " registration exists, but ALL_TG_PT=1 bit not"
                " present in received PROUT\n");
            core_scsi3_put_pr_reg(pr_reg);
            cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
            return -EINVAL;
        }
        /*
         * Allocate APTPL metadata buffer used for UNREGISTER ops
         */
        if (aptpl) {
            pr_aptpl_buf = kzalloc(pr_tmpl->pr_aptpl_buf_len,
                        GFP_KERNEL);
            if (!pr_aptpl_buf) {
                pr_err("Unable to allocate"
                    " pr_aptpl_buf\n");
                core_scsi3_put_pr_reg(pr_reg);
                cmd->scsi_sense_reason =
                    TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                return -EINVAL;
            }
        }
        /*
         * sa_res_key=0 Unregister Reservation Key for registered I_T
         * Nexus sa_res_key=1 Change Reservation Key for registered I_T
         * Nexus.
         */
        if (!sa_res_key) {
            pr_holder = core_scsi3_check_implict_release(
                    cmd->se_dev, pr_reg);
            if (pr_holder < 0) {
                kfree(pr_aptpl_buf);
                core_scsi3_put_pr_reg(pr_reg);
                cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
                return -EINVAL;
            }

            spin_lock(&pr_tmpl->registration_lock);
            /*
             * Release all ALL_TG_PT=1 for the matching SCSI Initiator Port
             * and matching pr_res_key.
             */
            if (pr_reg->pr_reg_all_tg_pt) {
                list_for_each_entry_safe(pr_reg_p, pr_reg_tmp,
                        &pr_tmpl->registration_list,
                        pr_reg_list) {

                    if (!pr_reg_p->pr_reg_all_tg_pt)
                        continue;

                    if (pr_reg_p->pr_res_key != res_key)
                        continue;

                    if (pr_reg == pr_reg_p)
                        continue;

                    if (strcmp(pr_reg->pr_reg_nacl->initiatorname,
                           pr_reg_p->pr_reg_nacl->initiatorname))
                        continue;

                    __core_scsi3_free_registration(dev,
                            pr_reg_p, NULL, 0);
                }
            }
            /*
             * Release the calling I_T Nexus registration now..
             */
            __core_scsi3_free_registration(cmd->se_dev, pr_reg,
                            NULL, 1);
            /*
             * From spc4r17, section 5.7.11.3 Unregistering
             *
             * If the persistent reservation is a registrants only
             * type, the device server shall establish a unit
             * attention condition for the initiator port associated
             * with every registered I_T nexus except for the I_T
             * nexus on which the PERSISTENT RESERVE OUT command was
             * received, with the additional sense code set to
             * RESERVATIONS RELEASED.
             */
            if (pr_holder &&
               ((type == PR_TYPE_WRITE_EXCLUSIVE_REGONLY) ||
                (type == PR_TYPE_EXCLUSIVE_ACCESS_REGONLY))) {
                list_for_each_entry(pr_reg_p,
                        &pr_tmpl->registration_list,
                        pr_reg_list) {

                    core_scsi3_ua_allocate(
                        pr_reg_p->pr_reg_nacl,
                        pr_reg_p->pr_res_mapped_lun,
                        0x2A,
                        ASCQ_2AH_RESERVATIONS_RELEASED);
                }
            }
            spin_unlock(&pr_tmpl->registration_lock);

            if (!aptpl) {
                pr_tmpl->pr_aptpl_active = 0;
                core_scsi3_update_and_write_aptpl(dev, NULL, 0);
                pr_debug("SPC-3 PR: Set APTPL Bit Deactivated"
                        " for UNREGISTER\n");
                return 0;
            }

            ret = core_scsi3_update_and_write_aptpl(dev,
                    &pr_aptpl_buf[0],
                    pr_tmpl->pr_aptpl_buf_len);
            if (!ret) {
                pr_tmpl->pr_aptpl_active = 1;
                pr_debug("SPC-3 PR: Set APTPL Bit Activated"
                        " for UNREGISTER\n");
            }

            kfree(pr_aptpl_buf);
            return ret;
        } else {
            /*
             * Increment PRgeneration counter for struct se_device"
             * upon a successful REGISTER, see spc4r17 section 6.3.2
             * READ_KEYS service action.
             */
            pr_reg->pr_res_generation = core_scsi3_pr_generation(
                            cmd->se_dev);
            pr_reg->pr_res_key = sa_res_key;
            pr_debug("SPC-3 PR [%s] REGISTER%s: Changed Reservation"
                " Key for %s to: 0x%016Lx PRgeneration:"
                " 0x%08x\n", cmd->se_tfo->get_fabric_name(),
                (ignore_key) ? "_AND_IGNORE_EXISTING_KEY" : "",
                pr_reg->pr_reg_nacl->initiatorname,
                pr_reg->pr_res_key, pr_reg->pr_res_generation);

            if (!aptpl) {
                pr_tmpl->pr_aptpl_active = 0;
                core_scsi3_update_and_write_aptpl(dev, NULL, 0);
                core_scsi3_put_pr_reg(pr_reg);
                pr_debug("SPC-3 PR: Set APTPL Bit Deactivated"
                        " for REGISTER\n");
                return 0;
            }

            ret = core_scsi3_update_and_write_aptpl(dev,
                    &pr_aptpl_buf[0],
                    pr_tmpl->pr_aptpl_buf_len);
            if (!ret) {
                pr_tmpl->pr_aptpl_active = 1;
                pr_debug("SPC-3 PR: Set APTPL Bit Activated"
                        " for REGISTER\n");
            }

            kfree(pr_aptpl_buf);
            core_scsi3_put_pr_reg(pr_reg);
        }
    }
    return 0;
}

unsigned char *core_scsi3_pr_dump_type(int type)
{
    switch (type) {
    case PR_TYPE_WRITE_EXCLUSIVE:
        return "Write Exclusive Access";
    case PR_TYPE_EXCLUSIVE_ACCESS:
        return "Exclusive Access";
    case PR_TYPE_WRITE_EXCLUSIVE_REGONLY:
        return "Write Exclusive Access, Registrants Only";
    case PR_TYPE_EXCLUSIVE_ACCESS_REGONLY:
        return "Exclusive Access, Registrants Only";
    case PR_TYPE_WRITE_EXCLUSIVE_ALLREG:
        return "Write Exclusive Access, All Registrants";
    case PR_TYPE_EXCLUSIVE_ACCESS_ALLREG:
        return "Exclusive Access, All Registrants";
    default:
        break;
    }

    return "Unknown SPC-3 PR Type";
}

static int core_scsi3_pro_reserve(
    struct se_cmd *cmd,
    struct se_device *dev,
    int type,
    int scope,
    u64 res_key)
{
    struct se_session *se_sess = cmd->se_sess;
    struct se_lun *se_lun = cmd->se_lun;
    struct t10_pr_registration *pr_reg, *pr_res_holder;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    char i_buf[PR_REG_ISID_ID_LEN];
    int ret, prf_isid;

    memset(i_buf, 0, PR_REG_ISID_ID_LEN);

    if (!se_sess || !se_lun) {
        pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    /*
     * Locate the existing *pr_reg via struct se_node_acl pointers
     */
    pr_reg = core_scsi3_locate_pr_reg(cmd->se_dev, se_sess->se_node_acl,
                se_sess);
    if (!pr_reg) {
        pr_err("SPC-3 PR: Unable to locate"
            " PR_REGISTERED *pr_reg for RESERVE\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    /*
     * From spc4r17 Section 5.7.9: Reserving:
     *
     * An application client creates a persistent reservation by issuing
     * a PERSISTENT RESERVE OUT command with RESERVE service action through
     * a registered I_T nexus with the following parameters:
     *    a) RESERVATION KEY set to the value of the reservation key that is
     *   registered with the logical unit for the I_T nexus; and
     */
    if (res_key != pr_reg->pr_res_key) {
        pr_err("SPC-3 PR RESERVE: Received res_key: 0x%016Lx"
            " does not match existing SA REGISTER res_key:"
            " 0x%016Lx\n", res_key, pr_reg->pr_res_key);
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }
    /*
     * From spc4r17 Section 5.7.9: Reserving:
     *
     * From above:
     *  b) TYPE field and SCOPE field set to the persistent reservation
     *     being created.
     *
     * Only one persistent reservation is allowed at a time per logical unit
     * and that persistent reservation has a scope of LU_SCOPE.
     */
    if (scope != PR_SCOPE_LU_SCOPE) {
        pr_err("SPC-3 PR: Illegal SCOPE: 0x%02x\n", scope);
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        return -EINVAL;
    }
    /*
     * See if we have an existing PR reservation holder pointer at
     * struct se_device->dev_pr_res_holder in the form struct t10_pr_registration
     * *pr_res_holder.
     */
    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if (pr_res_holder) {
        /*
         * From spc4r17 Section 5.7.9: Reserving:
         *
         * If the device server receives a PERSISTENT RESERVE OUT
         * command from an I_T nexus other than a persistent reservation
         * holder (see 5.7.10) that attempts to create a persistent
         * reservation when a persistent reservation already exists for
         * the logical unit, then the command shall be completed with
         * RESERVATION CONFLICT status.
         */
        if (pr_res_holder != pr_reg) {
            struct se_node_acl *pr_res_nacl = pr_res_holder->pr_reg_nacl;
            pr_err("SPC-3 PR: Attempted RESERVE from"
                " [%s]: %s while reservation already held by"
                " [%s]: %s, returning RESERVATION_CONFLICT\n",
                cmd->se_tfo->get_fabric_name(),
                se_sess->se_node_acl->initiatorname,
                pr_res_nacl->se_tpg->se_tpg_tfo->get_fabric_name(),
                pr_res_holder->pr_reg_nacl->initiatorname);

            spin_unlock(&dev->dev_reservation_lock);
            core_scsi3_put_pr_reg(pr_reg);
            cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
            return -EINVAL;
        }
        /*
         * From spc4r17 Section 5.7.9: Reserving:
         *
         * If a persistent reservation holder attempts to modify the
         * type or scope of an existing persistent reservation, the
         * command shall be completed with RESERVATION CONFLICT status.
         */
        if ((pr_res_holder->pr_res_type != type) ||
            (pr_res_holder->pr_res_scope != scope)) {
            struct se_node_acl *pr_res_nacl = pr_res_holder->pr_reg_nacl;
            pr_err("SPC-3 PR: Attempted RESERVE from"
                " [%s]: %s trying to change TYPE and/or SCOPE,"
                " while reservation already held by [%s]: %s,"
                " returning RESERVATION_CONFLICT\n",
                cmd->se_tfo->get_fabric_name(),
                se_sess->se_node_acl->initiatorname,
                pr_res_nacl->se_tpg->se_tpg_tfo->get_fabric_name(),
                pr_res_holder->pr_reg_nacl->initiatorname);

            spin_unlock(&dev->dev_reservation_lock);
            core_scsi3_put_pr_reg(pr_reg);
            cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
            return -EINVAL;
        }
        /*
         * From spc4r17 Section 5.7.9: Reserving:
         *
         * If the device server receives a PERSISTENT RESERVE OUT
         * command with RESERVE service action where the TYPE field and
         * the SCOPE field contain the same values as the existing type
         * and scope from a persistent reservation holder, it shall not
         * make any change to the existing persistent reservation and
         * shall completethe command with GOOD status.
         */
        spin_unlock(&dev->dev_reservation_lock);
        core_scsi3_put_pr_reg(pr_reg);
        return 0;
    }
    /*
     * Otherwise, our *pr_reg becomes the PR reservation holder for said
     * TYPE/SCOPE.  Also set the received scope and type in *pr_reg.
     */
    pr_reg->pr_res_scope = scope;
    pr_reg->pr_res_type = type;
    pr_reg->pr_res_holder = 1;
    dev->dev_pr_res_holder = pr_reg;
    prf_isid = core_pr_dump_initiator_port(pr_reg, &i_buf[0],
                PR_REG_ISID_ID_LEN);

    pr_debug("SPC-3 PR [%s] Service Action: RESERVE created new"
        " reservation holder TYPE: %s ALL_TG_PT: %d\n",
        cmd->se_tfo->get_fabric_name(), core_scsi3_pr_dump_type(type),
        (pr_reg->pr_reg_all_tg_pt) ? 1 : 0);
    pr_debug("SPC-3 PR [%s] RESERVE Node: %s%s\n",
            cmd->se_tfo->get_fabric_name(),
            se_sess->se_node_acl->initiatorname,
            (prf_isid) ? &i_buf[0] : "");
    spin_unlock(&dev->dev_reservation_lock);

    if (pr_tmpl->pr_aptpl_active) {
        ret = core_scsi3_update_and_write_aptpl(cmd->se_dev,
                &pr_reg->pr_aptpl_buf[0],
                pr_tmpl->pr_aptpl_buf_len);
        if (!ret)
            pr_debug("SPC-3 PR: Updated APTPL metadata"
                    " for RESERVE\n");
    }

    core_scsi3_put_pr_reg(pr_reg);
    return 0;
}

static int core_scsi3_emulate_pro_reserve(
    struct se_cmd *cmd,
    int type,
    int scope,
    u64 res_key)
{
    struct se_device *dev = cmd->se_dev;
    int ret = 0;

    switch (type) {
    case PR_TYPE_WRITE_EXCLUSIVE:
    case PR_TYPE_EXCLUSIVE_ACCESS:
    case PR_TYPE_WRITE_EXCLUSIVE_REGONLY:
    case PR_TYPE_EXCLUSIVE_ACCESS_REGONLY:
    case PR_TYPE_WRITE_EXCLUSIVE_ALLREG:
    case PR_TYPE_EXCLUSIVE_ACCESS_ALLREG:
        ret = core_scsi3_pro_reserve(cmd, dev, type, scope, res_key);
        break;
    default:
        pr_err("SPC-3 PR: Unknown Service Action RESERVE Type:"
            " 0x%02x\n", type);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        return -EINVAL;
    }

    return ret;
}

/*
 * Called with struct se_device->dev_reservation_lock held.
 */
static void __core_scsi3_complete_pro_release(
    struct se_device *dev,
    struct se_node_acl *se_nacl,
    struct t10_pr_registration *pr_reg,
    int explict)
{
    struct target_core_fabric_ops *tfo = se_nacl->se_tpg->se_tpg_tfo;
    char i_buf[PR_REG_ISID_ID_LEN];
    int prf_isid;

    memset(i_buf, 0, PR_REG_ISID_ID_LEN);
    prf_isid = core_pr_dump_initiator_port(pr_reg, &i_buf[0],
                PR_REG_ISID_ID_LEN);
    /*
     * Go ahead and release the current PR reservation holder.
     */
    dev->dev_pr_res_holder = NULL;

    pr_debug("SPC-3 PR [%s] Service Action: %s RELEASE cleared"
        " reservation holder TYPE: %s ALL_TG_PT: %d\n",
        tfo->get_fabric_name(), (explict) ? "explict" : "implict",
        core_scsi3_pr_dump_type(pr_reg->pr_res_type),
        (pr_reg->pr_reg_all_tg_pt) ? 1 : 0);
    pr_debug("SPC-3 PR [%s] RELEASE Node: %s%s\n",
        tfo->get_fabric_name(), se_nacl->initiatorname,
        (prf_isid) ? &i_buf[0] : "");
    /*
     * Clear TYPE and SCOPE for the next PROUT Service Action: RESERVE
     */
    pr_reg->pr_res_holder = pr_reg->pr_res_type = pr_reg->pr_res_scope = 0;
}

static int core_scsi3_emulate_pro_release(
    struct se_cmd *cmd,
    int type,
    int scope,
    u64 res_key)
{
    struct se_device *dev = cmd->se_dev;
    struct se_session *se_sess = cmd->se_sess;
    struct se_lun *se_lun = cmd->se_lun;
    struct t10_pr_registration *pr_reg, *pr_reg_p, *pr_res_holder;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    int ret, all_reg = 0;

    if (!se_sess || !se_lun) {
        pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    /*
     * Locate the existing *pr_reg via struct se_node_acl pointers
     */
    pr_reg = core_scsi3_locate_pr_reg(dev, se_sess->se_node_acl, se_sess);
    if (!pr_reg) {
        pr_err("SPC-3 PR: Unable to locate"
            " PR_REGISTERED *pr_reg for RELEASE\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    /*
     * From spc4r17 Section 5.7.11.2 Releasing:
     *
     * If there is no persistent reservation or in response to a persistent
     * reservation release request from a registered I_T nexus that is not a
     * persistent reservation holder (see 5.7.10), the device server shall
     * do the following:
     *
     *     a) Not release the persistent reservation, if any;
     *     b) Not remove any registrations; and
     *     c) Complete the command with GOOD status.
     */
    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if (!pr_res_holder) {
        /*
         * No persistent reservation, return GOOD status.
         */
        spin_unlock(&dev->dev_reservation_lock);
        core_scsi3_put_pr_reg(pr_reg);
        return 0;
    }
    if ((pr_res_holder->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG) ||
        (pr_res_holder->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG))
        all_reg = 1;

    if ((all_reg == 0) && (pr_res_holder != pr_reg)) {
        /*
         * Non 'All Registrants' PR Type cases..
         * Release request from a registered I_T nexus that is not a
         * persistent reservation holder. return GOOD status.
         */
        spin_unlock(&dev->dev_reservation_lock);
        core_scsi3_put_pr_reg(pr_reg);
        return 0;
    }
    /*
     * From spc4r17 Section 5.7.11.2 Releasing:
     *
     * Only the persistent reservation holder (see 5.7.10) is allowed to
     * release a persistent reservation.
     *
     * An application client releases the persistent reservation by issuing
     * a PERSISTENT RESERVE OUT command with RELEASE service action through
     * an I_T nexus that is a persistent reservation holder with the
     * following parameters:
     *
     *     a) RESERVATION KEY field set to the value of the reservation key
     *    that is registered with the logical unit for the I_T nexus;
     */
    if (res_key != pr_reg->pr_res_key) {
        pr_err("SPC-3 PR RELEASE: Received res_key: 0x%016Lx"
            " does not match existing SA REGISTER res_key:"
            " 0x%016Lx\n", res_key, pr_reg->pr_res_key);
        spin_unlock(&dev->dev_reservation_lock);
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }
    /*
     * From spc4r17 Section 5.7.11.2 Releasing and above:
     *
     * b) TYPE field and SCOPE field set to match the persistent
     *    reservation being released.
     */
    if ((pr_res_holder->pr_res_type != type) ||
        (pr_res_holder->pr_res_scope != scope)) {
        struct se_node_acl *pr_res_nacl = pr_res_holder->pr_reg_nacl;
        pr_err("SPC-3 PR RELEASE: Attempted to release"
            " reservation from [%s]: %s with different TYPE "
            "and/or SCOPE  while reservation already held by"
            " [%s]: %s, returning RESERVATION_CONFLICT\n",
            cmd->se_tfo->get_fabric_name(),
            se_sess->se_node_acl->initiatorname,
            pr_res_nacl->se_tpg->se_tpg_tfo->get_fabric_name(),
            pr_res_holder->pr_reg_nacl->initiatorname);

        spin_unlock(&dev->dev_reservation_lock);
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }
    /*
     * In response to a persistent reservation release request from the
     * persistent reservation holder the device server shall perform a
     * release by doing the following as an uninterrupted series of actions:
     * a) Release the persistent reservation;
     * b) Not remove any registration(s);
     * c) If the released persistent reservation is a registrants only type
     * or all registrants type persistent reservation,
     *    the device server shall establish a unit attention condition for
     *    the initiator port associated with every regis-
     *    tered I_T nexus other than I_T nexus on which the PERSISTENT
     *    RESERVE OUT command with RELEASE service action was received,
     *    with the additional sense code set to RESERVATIONS RELEASED; and
     * d) If the persistent reservation is of any other type, the device
     *    server shall not establish a unit attention condition.
     */
    __core_scsi3_complete_pro_release(dev, se_sess->se_node_acl,
            pr_reg, 1);

    spin_unlock(&dev->dev_reservation_lock);

    if ((type != PR_TYPE_WRITE_EXCLUSIVE_REGONLY) &&
        (type != PR_TYPE_EXCLUSIVE_ACCESS_REGONLY) &&
        (type != PR_TYPE_WRITE_EXCLUSIVE_ALLREG) &&
        (type != PR_TYPE_EXCLUSIVE_ACCESS_ALLREG)) {
        /*
         * If no UNIT ATTENTION conditions will be established for
         * PR_TYPE_WRITE_EXCLUSIVE or PR_TYPE_EXCLUSIVE_ACCESS
         * go ahead and check for APTPL=1 update+write below
         */
        goto write_aptpl;
    }

    spin_lock(&pr_tmpl->registration_lock);
    list_for_each_entry(pr_reg_p, &pr_tmpl->registration_list,
            pr_reg_list) {
        /*
         * Do not establish a UNIT ATTENTION condition
         * for the calling I_T Nexus
         */
        if (pr_reg_p == pr_reg)
            continue;

        core_scsi3_ua_allocate(pr_reg_p->pr_reg_nacl,
                pr_reg_p->pr_res_mapped_lun,
                0x2A, ASCQ_2AH_RESERVATIONS_RELEASED);
    }
    spin_unlock(&pr_tmpl->registration_lock);

write_aptpl:
    if (pr_tmpl->pr_aptpl_active) {
        ret = core_scsi3_update_and_write_aptpl(cmd->se_dev,
                &pr_reg->pr_aptpl_buf[0],
                pr_tmpl->pr_aptpl_buf_len);
        if (!ret)
            pr_debug("SPC-3 PR: Updated APTPL metadata for RELEASE\n");
    }

    core_scsi3_put_pr_reg(pr_reg);
    return 0;
}

static int core_scsi3_emulate_pro_clear(
    struct se_cmd *cmd,
    u64 res_key)
{
    struct se_device *dev = cmd->se_dev;
    struct se_node_acl *pr_reg_nacl;
    struct se_session *se_sess = cmd->se_sess;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    struct t10_pr_registration *pr_reg, *pr_reg_tmp, *pr_reg_n, *pr_res_holder;
    u32 pr_res_mapped_lun = 0;
    int calling_it_nexus = 0;
    /*
     * Locate the existing *pr_reg via struct se_node_acl pointers
     */
    pr_reg_n = core_scsi3_locate_pr_reg(cmd->se_dev,
            se_sess->se_node_acl, se_sess);
    if (!pr_reg_n) {
        pr_err("SPC-3 PR: Unable to locate"
            " PR_REGISTERED *pr_reg for CLEAR\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    /*
     * From spc4r17 section 5.7.11.6, Clearing:
     *
     * Any application client may release the persistent reservation and
     * remove all registrations from a device server by issuing a
     * PERSISTENT RESERVE OUT command with CLEAR service action through a
     * registered I_T nexus with the following parameter:
     *
     *  a) RESERVATION KEY field set to the value of the reservation key
     *     that is registered with the logical unit for the I_T nexus.
     */
    if (res_key != pr_reg_n->pr_res_key) {
        pr_err("SPC-3 PR REGISTER: Received"
            " res_key: 0x%016Lx does not match"
            " existing SA REGISTER res_key:"
            " 0x%016Lx\n", res_key, pr_reg_n->pr_res_key);
        core_scsi3_put_pr_reg(pr_reg_n);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }
    /*
     * a) Release the persistent reservation, if any;
     */
    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if (pr_res_holder) {
        struct se_node_acl *pr_res_nacl = pr_res_holder->pr_reg_nacl;
        __core_scsi3_complete_pro_release(dev, pr_res_nacl,
            pr_res_holder, 0);
    }
    spin_unlock(&dev->dev_reservation_lock);
    /*
     * b) Remove all registration(s) (see spc4r17 5.7.7);
     */
    spin_lock(&pr_tmpl->registration_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp,
            &pr_tmpl->registration_list, pr_reg_list) {

        calling_it_nexus = (pr_reg_n == pr_reg) ? 1 : 0;
        pr_reg_nacl = pr_reg->pr_reg_nacl;
        pr_res_mapped_lun = pr_reg->pr_res_mapped_lun;
        __core_scsi3_free_registration(dev, pr_reg, NULL,
                    calling_it_nexus);
        /*
         * e) Establish a unit attention condition for the initiator
         *    port associated with every registered I_T nexus other
         *    than the I_T nexus on which the PERSISTENT RESERVE OUT
         *    command with CLEAR service action was received, with the
         *    additional sense code set to RESERVATIONS PREEMPTED.
         */
        if (!calling_it_nexus)
            core_scsi3_ua_allocate(pr_reg_nacl, pr_res_mapped_lun,
                0x2A, ASCQ_2AH_RESERVATIONS_PREEMPTED);
    }
    spin_unlock(&pr_tmpl->registration_lock);

    pr_debug("SPC-3 PR [%s] Service Action: CLEAR complete\n",
        cmd->se_tfo->get_fabric_name());

    if (pr_tmpl->pr_aptpl_active) {
        core_scsi3_update_and_write_aptpl(cmd->se_dev, NULL, 0);
        pr_debug("SPC-3 PR: Updated APTPL metadata"
                " for CLEAR\n");
    }

    core_scsi3_pr_generation(dev);
    return 0;
}

/*
 * Called with struct se_device->dev_reservation_lock held.
 */
static void __core_scsi3_complete_pro_preempt(
    struct se_device *dev,
    struct t10_pr_registration *pr_reg,
    struct list_head *preempt_and_abort_list,
    int type,
    int scope,
    int abort)
{
    struct se_node_acl *nacl = pr_reg->pr_reg_nacl;
    struct target_core_fabric_ops *tfo = nacl->se_tpg->se_tpg_tfo;
    char i_buf[PR_REG_ISID_ID_LEN];
    int prf_isid;

    memset(i_buf, 0, PR_REG_ISID_ID_LEN);
    prf_isid = core_pr_dump_initiator_port(pr_reg, &i_buf[0],
                PR_REG_ISID_ID_LEN);
    /*
     * Do an implict RELEASE of the existing reservation.
     */
    if (dev->dev_pr_res_holder)
        __core_scsi3_complete_pro_release(dev, nacl,
                dev->dev_pr_res_holder, 0);

    dev->dev_pr_res_holder = pr_reg;
    pr_reg->pr_res_holder = 1;
    pr_reg->pr_res_type = type;
    pr_reg->pr_res_scope = scope;

    pr_debug("SPC-3 PR [%s] Service Action: PREEMPT%s created new"
        " reservation holder TYPE: %s ALL_TG_PT: %d\n",
        tfo->get_fabric_name(), (abort) ? "_AND_ABORT" : "",
        core_scsi3_pr_dump_type(type),
        (pr_reg->pr_reg_all_tg_pt) ? 1 : 0);
    pr_debug("SPC-3 PR [%s] PREEMPT%s from Node: %s%s\n",
        tfo->get_fabric_name(), (abort) ? "_AND_ABORT" : "",
        nacl->initiatorname, (prf_isid) ? &i_buf[0] : "");
    /*
     * For PREEMPT_AND_ABORT, add the preempting reservation's
     * struct t10_pr_registration to the list that will be compared
     * against received CDBs..
     */
    if (preempt_and_abort_list)
        list_add_tail(&pr_reg->pr_reg_abort_list,
                preempt_and_abort_list);
}

static void core_scsi3_release_preempt_and_abort(
    struct list_head *preempt_and_abort_list,
    struct t10_pr_registration *pr_reg_holder)
{
    struct t10_pr_registration *pr_reg, *pr_reg_tmp;

    list_for_each_entry_safe(pr_reg, pr_reg_tmp, preempt_and_abort_list,
                pr_reg_abort_list) {

        list_del(&pr_reg->pr_reg_abort_list);
        if (pr_reg_holder == pr_reg)
            continue;
        if (pr_reg->pr_res_holder) {
            pr_warn("pr_reg->pr_res_holder still set\n");
            continue;
        }

        pr_reg->pr_reg_deve = NULL;
        pr_reg->pr_reg_nacl = NULL;
        kfree(pr_reg->pr_aptpl_buf);
        kmem_cache_free(t10_pr_reg_cache, pr_reg);
    }
}

static int core_scsi3_pro_preempt(
    struct se_cmd *cmd,
    int type,
    int scope,
    u64 res_key,
    u64 sa_res_key,
    int abort)
{
    struct se_device *dev = cmd->se_dev;
    struct se_node_acl *pr_reg_nacl;
    struct se_session *se_sess = cmd->se_sess;
    LIST_HEAD(preempt_and_abort_list);
    struct t10_pr_registration *pr_reg, *pr_reg_tmp, *pr_reg_n, *pr_res_holder;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    u32 pr_res_mapped_lun = 0;
    int all_reg = 0, calling_it_nexus = 0, released_regs = 0;
    int prh_type = 0, prh_scope = 0, ret;

    if (!se_sess) {
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }

    pr_reg_n = core_scsi3_locate_pr_reg(cmd->se_dev, se_sess->se_node_acl,
                se_sess);
    if (!pr_reg_n) {
        pr_err("SPC-3 PR: Unable to locate"
            " PR_REGISTERED *pr_reg for PREEMPT%s\n",
            (abort) ? "_AND_ABORT" : "");
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }
    if (pr_reg_n->pr_res_key != res_key) {
        core_scsi3_put_pr_reg(pr_reg_n);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }
    if (scope != PR_SCOPE_LU_SCOPE) {
        pr_err("SPC-3 PR: Illegal SCOPE: 0x%02x\n", scope);
        core_scsi3_put_pr_reg(pr_reg_n);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        return -EINVAL;
    }

    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if (pr_res_holder &&
       ((pr_res_holder->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG) ||
        (pr_res_holder->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG)))
        all_reg = 1;

    if (!all_reg && !sa_res_key) {
        spin_unlock(&dev->dev_reservation_lock);
        core_scsi3_put_pr_reg(pr_reg_n);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        return -EINVAL;
    }
    /*
     * From spc4r17, section 5.7.11.4.4 Removing Registrations:
     *
     * If the SERVICE ACTION RESERVATION KEY field does not identify a
     * persistent reservation holder or there is no persistent reservation
     * holder (i.e., there is no persistent reservation), then the device
     * server shall perform a preempt by doing the following in an
     * uninterrupted series of actions. (See below..)
     */
    if (!pr_res_holder || (pr_res_holder->pr_res_key != sa_res_key)) {
        /*
         * No existing or SA Reservation Key matching reservations..
         *
         * PROUT SA PREEMPT with All Registrant type reservations are
         * allowed to be processed without a matching SA Reservation Key
         */
        spin_lock(&pr_tmpl->registration_lock);
        list_for_each_entry_safe(pr_reg, pr_reg_tmp,
                &pr_tmpl->registration_list, pr_reg_list) {
            /*
             * Removing of registrations in non all registrants
             * type reservations without a matching SA reservation
             * key.
             *
             * a) Remove the registrations for all I_T nexuses
             *    specified by the SERVICE ACTION RESERVATION KEY
             *    field;
             * b) Ignore the contents of the SCOPE and TYPE fields;
             * c) Process tasks as defined in 5.7.1; and
             * d) Establish a unit attention condition for the
             *    initiator port associated with every I_T nexus
             *    that lost its registration other than the I_T
             *    nexus on which the PERSISTENT RESERVE OUT command
             *    was received, with the additional sense code set
             *    to REGISTRATIONS PREEMPTED.
             */
            if (!all_reg) {
                if (pr_reg->pr_res_key != sa_res_key)
                    continue;

                calling_it_nexus = (pr_reg_n == pr_reg) ? 1 : 0;
                pr_reg_nacl = pr_reg->pr_reg_nacl;
                pr_res_mapped_lun = pr_reg->pr_res_mapped_lun;
                __core_scsi3_free_registration(dev, pr_reg,
                    (abort) ? &preempt_and_abort_list :
                        NULL, calling_it_nexus);
                released_regs++;
            } else {
                /*
                 * Case for any existing all registrants type
                 * reservation, follow logic in spc4r17 section
                 * 5.7.11.4 Preempting, Table 52 and Figure 7.
                 *
                 * For a ZERO SA Reservation key, release
                 * all other registrations and do an implict
                 * release of active persistent reservation.
                 *
                 * For a non-ZERO SA Reservation key, only
                 * release the matching reservation key from
                 * registrations.
                 */
                if ((sa_res_key) &&
                     (pr_reg->pr_res_key != sa_res_key))
                    continue;

                calling_it_nexus = (pr_reg_n == pr_reg) ? 1 : 0;
                if (calling_it_nexus)
                    continue;

                pr_reg_nacl = pr_reg->pr_reg_nacl;
                pr_res_mapped_lun = pr_reg->pr_res_mapped_lun;
                __core_scsi3_free_registration(dev, pr_reg,
                    (abort) ? &preempt_and_abort_list :
                        NULL, 0);
                released_regs++;
            }
            if (!calling_it_nexus)
                core_scsi3_ua_allocate(pr_reg_nacl,
                    pr_res_mapped_lun, 0x2A,
                    ASCQ_2AH_REGISTRATIONS_PREEMPTED);
        }
        spin_unlock(&pr_tmpl->registration_lock);
        /*
         * If a PERSISTENT RESERVE OUT with a PREEMPT service action or
         * a PREEMPT AND ABORT service action sets the SERVICE ACTION
         * RESERVATION KEY field to a value that does not match any
         * registered reservation key, then the device server shall
         * complete the command with RESERVATION CONFLICT status.
         */
        if (!released_regs) {
            spin_unlock(&dev->dev_reservation_lock);
            core_scsi3_put_pr_reg(pr_reg_n);
            cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
            return -EINVAL;
        }
        /*
         * For an existing all registrants type reservation
         * with a zero SA rservation key, preempt the existing
         * reservation with the new PR type and scope.
         */
        if (pr_res_holder && all_reg && !(sa_res_key)) {
            __core_scsi3_complete_pro_preempt(dev, pr_reg_n,
                (abort) ? &preempt_and_abort_list : NULL,
                type, scope, abort);

            if (abort)
                core_scsi3_release_preempt_and_abort(
                    &preempt_and_abort_list, pr_reg_n);
        }
        spin_unlock(&dev->dev_reservation_lock);

        if (pr_tmpl->pr_aptpl_active) {
            ret = core_scsi3_update_and_write_aptpl(cmd->se_dev,
                    &pr_reg_n->pr_aptpl_buf[0],
                    pr_tmpl->pr_aptpl_buf_len);
            if (!ret)
                pr_debug("SPC-3 PR: Updated APTPL"
                    " metadata for  PREEMPT%s\n", (abort) ?
                    "_AND_ABORT" : "");
        }

        core_scsi3_put_pr_reg(pr_reg_n);
        core_scsi3_pr_generation(cmd->se_dev);
        return 0;
    }
    /*
     * The PREEMPTing SA reservation key matches that of the
     * existing persistent reservation, first, we check if
     * we are preempting our own reservation.
     * From spc4r17, section 5.7.11.4.3 Preempting
     * persistent reservations and registration handling
     *
     * If an all registrants persistent reservation is not
     * present, it is not an error for the persistent
     * reservation holder to preempt itself (i.e., a
     * PERSISTENT RESERVE OUT with a PREEMPT service action
     * or a PREEMPT AND ABORT service action with the
     * SERVICE ACTION RESERVATION KEY value equal to the
     * persistent reservation holder's reservation key that
     * is received from the persistent reservation holder).
     * In that case, the device server shall establish the
     * new persistent reservation and maintain the
     * registration.
     */
    prh_type = pr_res_holder->pr_res_type;
    prh_scope = pr_res_holder->pr_res_scope;
    /*
     * If the SERVICE ACTION RESERVATION KEY field identifies a
     * persistent reservation holder (see 5.7.10), the device
     * server shall perform a preempt by doing the following as
     * an uninterrupted series of actions:
     *
     * a) Release the persistent reservation for the holder
     *    identified by the SERVICE ACTION RESERVATION KEY field;
     */
    if (pr_reg_n != pr_res_holder)
        __core_scsi3_complete_pro_release(dev,
                pr_res_holder->pr_reg_nacl,
                dev->dev_pr_res_holder, 0);
    /*
     * b) Remove the registrations for all I_T nexuses identified
     *    by the SERVICE ACTION RESERVATION KEY field, except the
     *    I_T nexus that is being used for the PERSISTENT RESERVE
     *    OUT command. If an all registrants persistent reservation
     *    is present and the SERVICE ACTION RESERVATION KEY field
     *    is set to zero, then all registrations shall be removed
     *    except for that of the I_T nexus that is being used for
     *    the PERSISTENT RESERVE OUT command;
     */
    spin_lock(&pr_tmpl->registration_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp,
            &pr_tmpl->registration_list, pr_reg_list) {

        calling_it_nexus = (pr_reg_n == pr_reg) ? 1 : 0;
        if (calling_it_nexus)
            continue;

        if (pr_reg->pr_res_key != sa_res_key)
            continue;

        pr_reg_nacl = pr_reg->pr_reg_nacl;
        pr_res_mapped_lun = pr_reg->pr_res_mapped_lun;
        __core_scsi3_free_registration(dev, pr_reg,
                (abort) ? &preempt_and_abort_list : NULL,
                calling_it_nexus);
        /*
         * e) Establish a unit attention condition for the initiator
         *    port associated with every I_T nexus that lost its
         *    persistent reservation and/or registration, with the
         *    additional sense code set to REGISTRATIONS PREEMPTED;
         */
        core_scsi3_ua_allocate(pr_reg_nacl, pr_res_mapped_lun, 0x2A,
                ASCQ_2AH_REGISTRATIONS_PREEMPTED);
    }
    spin_unlock(&pr_tmpl->registration_lock);
    /*
     * c) Establish a persistent reservation for the preempting
     *    I_T nexus using the contents of the SCOPE and TYPE fields;
     */
    __core_scsi3_complete_pro_preempt(dev, pr_reg_n,
            (abort) ? &preempt_and_abort_list : NULL,
            type, scope, abort);
    /*
     * d) Process tasks as defined in 5.7.1;
     * e) See above..
     * f) If the type or scope has changed, then for every I_T nexus
     *    whose reservation key was not removed, except for the I_T
     *    nexus on which the PERSISTENT RESERVE OUT command was
     *    received, the device server shall establish a unit
     *    attention condition for the initiator port associated with
     *    that I_T nexus, with the additional sense code set to
     *    RESERVATIONS RELEASED. If the type or scope have not
     *    changed, then no unit attention condition(s) shall be
     *    established for this reason.
     */
    if ((prh_type != type) || (prh_scope != scope)) {
        spin_lock(&pr_tmpl->registration_lock);
        list_for_each_entry_safe(pr_reg, pr_reg_tmp,
                &pr_tmpl->registration_list, pr_reg_list) {

            calling_it_nexus = (pr_reg_n == pr_reg) ? 1 : 0;
            if (calling_it_nexus)
                continue;

            core_scsi3_ua_allocate(pr_reg->pr_reg_nacl,
                    pr_reg->pr_res_mapped_lun, 0x2A,
                    ASCQ_2AH_RESERVATIONS_RELEASED);
        }
        spin_unlock(&pr_tmpl->registration_lock);
    }
    spin_unlock(&dev->dev_reservation_lock);
    /*
     * Call LUN_RESET logic upon list of struct t10_pr_registration,
     * All received CDBs for the matching existing reservation and
     * registrations undergo ABORT_TASK logic.
     *
     * From there, core_scsi3_release_preempt_and_abort() will
     * release every registration in the list (which have already
     * been removed from the primary pr_reg list), except the
     * new persistent reservation holder, the calling Initiator Port.
     */
    if (abort) {
        core_tmr_lun_reset(dev, NULL, &preempt_and_abort_list, cmd);
        core_scsi3_release_preempt_and_abort(&preempt_and_abort_list,
                        pr_reg_n);
    }

    if (pr_tmpl->pr_aptpl_active) {
        ret = core_scsi3_update_and_write_aptpl(cmd->se_dev,
                &pr_reg_n->pr_aptpl_buf[0],
                pr_tmpl->pr_aptpl_buf_len);
        if (!ret)
            pr_debug("SPC-3 PR: Updated APTPL metadata for PREEMPT"
                "%s\n", (abort) ? "_AND_ABORT" : "");
    }

    core_scsi3_put_pr_reg(pr_reg_n);
    core_scsi3_pr_generation(cmd->se_dev);
    return 0;
}

static int core_scsi3_emulate_pro_preempt(
    struct se_cmd *cmd,
    int type,
    int scope,
    u64 res_key,
    u64 sa_res_key,
    int abort)
{
    int ret = 0;

    switch (type) {
    case PR_TYPE_WRITE_EXCLUSIVE:
    case PR_TYPE_EXCLUSIVE_ACCESS:
    case PR_TYPE_WRITE_EXCLUSIVE_REGONLY:
    case PR_TYPE_EXCLUSIVE_ACCESS_REGONLY:
    case PR_TYPE_WRITE_EXCLUSIVE_ALLREG:
    case PR_TYPE_EXCLUSIVE_ACCESS_ALLREG:
        ret = core_scsi3_pro_preempt(cmd, type, scope,
                res_key, sa_res_key, abort);
        break;
    default:
        pr_err("SPC-3 PR: Unknown Service Action PREEMPT%s"
            " Type: 0x%02x\n", (abort) ? "_AND_ABORT" : "", type);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        return -EINVAL;
    }

    return ret;
}


static int core_scsi3_emulate_pro_register_and_move(
    struct se_cmd *cmd,
    u64 res_key,
    u64 sa_res_key,
    int aptpl,
    int unreg)
{
    struct se_session *se_sess = cmd->se_sess;
    struct se_device *dev = cmd->se_dev;
    struct se_dev_entry *dest_se_deve = NULL;
    struct se_lun *se_lun = cmd->se_lun;
    struct se_node_acl *pr_res_nacl, *pr_reg_nacl, *dest_node_acl = NULL;
    struct se_port *se_port;
    struct se_portal_group *se_tpg, *dest_se_tpg = NULL;
    struct target_core_fabric_ops *dest_tf_ops = NULL, *tf_ops;
    struct t10_pr_registration *pr_reg, *pr_res_holder, *dest_pr_reg;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    unsigned char *buf;
    unsigned char *initiator_str;
    char *iport_ptr = NULL, dest_iport[64], i_buf[PR_REG_ISID_ID_LEN];
    u32 tid_len, tmp_tid_len;
    int new_reg = 0, type, scope, ret, matching_iname, prf_isid;
    unsigned short rtpi;
    unsigned char proto_ident;

    if (!se_sess || !se_lun) {
        pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    memset(dest_iport, 0, 64);
    memset(i_buf, 0, PR_REG_ISID_ID_LEN);
    se_tpg = se_sess->se_tpg;
    tf_ops = se_tpg->se_tpg_tfo;
    /*
     * Follow logic from spc4r17 Section 5.7.8, Table 50 --
     *  Register behaviors for a REGISTER AND MOVE service action
     *
     * Locate the existing *pr_reg via struct se_node_acl pointers
     */
    pr_reg = core_scsi3_locate_pr_reg(cmd->se_dev, se_sess->se_node_acl,
                se_sess);
    if (!pr_reg) {
        pr_err("SPC-3 PR: Unable to locate PR_REGISTERED"
            " *pr_reg for REGISTER_AND_MOVE\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -EINVAL;
    }
    /*
     * The provided reservation key much match the existing reservation key
     * provided during this initiator's I_T nexus registration.
     */
    if (res_key != pr_reg->pr_res_key) {
        pr_warn("SPC-3 PR REGISTER_AND_MOVE: Received"
            " res_key: 0x%016Lx does not match existing SA REGISTER"
            " res_key: 0x%016Lx\n", res_key, pr_reg->pr_res_key);
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }
    /*
     * The service active reservation key needs to be non zero
     */
    if (!sa_res_key) {
        pr_warn("SPC-3 PR REGISTER_AND_MOVE: Received zero"
            " sa_res_key\n");
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        return -EINVAL;
    }

    /*
     * Determine the Relative Target Port Identifier where the reservation
     * will be moved to for the TransportID containing SCSI initiator WWN
     * information.
     */
    buf = transport_kmap_data_sg(cmd);
    rtpi = (buf[18] & 0xff) << 8;
    rtpi |= buf[19] & 0xff;
    tid_len = (buf[20] & 0xff) << 24;
    tid_len |= (buf[21] & 0xff) << 16;
    tid_len |= (buf[22] & 0xff) << 8;
    tid_len |= buf[23] & 0xff;
    transport_kunmap_data_sg(cmd);
    buf = NULL;

    if ((tid_len + 24) != cmd->data_length) {
        pr_err("SPC-3 PR: Illegal tid_len: %u + 24 byte header"
            " does not equal CDB data_length: %u\n", tid_len,
            cmd->data_length);
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        return -EINVAL;
    }

    spin_lock(&dev->se_port_lock);
    list_for_each_entry(se_port, &dev->dev_sep_list, sep_list) {
        if (se_port->sep_rtpi != rtpi)
            continue;
        dest_se_tpg = se_port->sep_tpg;
        if (!dest_se_tpg)
            continue;
        dest_tf_ops = dest_se_tpg->se_tpg_tfo;
        if (!dest_tf_ops)
            continue;

        atomic_inc(&dest_se_tpg->tpg_pr_ref_count);
        smp_mb__after_atomic_inc();
        spin_unlock(&dev->se_port_lock);

        ret = core_scsi3_tpg_depend_item(dest_se_tpg);
        if (ret != 0) {
            pr_err("core_scsi3_tpg_depend_item() failed"
                " for dest_se_tpg\n");
            atomic_dec(&dest_se_tpg->tpg_pr_ref_count);
            smp_mb__after_atomic_dec();
            core_scsi3_put_pr_reg(pr_reg);
            cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
            return -EINVAL;
        }

        spin_lock(&dev->se_port_lock);
        break;
    }
    spin_unlock(&dev->se_port_lock);

    if (!dest_se_tpg || !dest_tf_ops) {
        pr_err("SPC-3 PR REGISTER_AND_MOVE: Unable to locate"
            " fabric ops from Relative Target Port Identifier:"
            " %hu\n", rtpi);
        core_scsi3_put_pr_reg(pr_reg);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        return -EINVAL;
    }

    buf = transport_kmap_data_sg(cmd);
    proto_ident = (buf[24] & 0x0f);

    pr_debug("SPC-3 PR REGISTER_AND_MOVE: Extracted Protocol Identifier:"
            " 0x%02x\n", proto_ident);

    if (proto_ident != dest_tf_ops->get_fabric_proto_ident(dest_se_tpg)) {
        pr_err("SPC-3 PR REGISTER_AND_MOVE: Received"
            " proto_ident: 0x%02x does not match ident: 0x%02x"
            " from fabric: %s\n", proto_ident,
            dest_tf_ops->get_fabric_proto_ident(dest_se_tpg),
            dest_tf_ops->get_fabric_name());
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }
    if (dest_tf_ops->tpg_parse_pr_out_transport_id == NULL) {
        pr_err("SPC-3 PR REGISTER_AND_MOVE: Fabric does not"
            " containg a valid tpg_parse_pr_out_transport_id"
            " function pointer\n");
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        ret = -EINVAL;
        goto out;
    }
    initiator_str = dest_tf_ops->tpg_parse_pr_out_transport_id(dest_se_tpg,
            (const char *)&buf[24], &tmp_tid_len, &iport_ptr);
    if (!initiator_str) {
        pr_err("SPC-3 PR REGISTER_AND_MOVE: Unable to locate"
            " initiator_str from Transport ID\n");
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }

    transport_kunmap_data_sg(cmd);
    buf = NULL;

    pr_debug("SPC-3 PR [%s] Extracted initiator %s identifier: %s"
        " %s\n", dest_tf_ops->get_fabric_name(), (iport_ptr != NULL) ?
        "port" : "device", initiator_str, (iport_ptr != NULL) ?
        iport_ptr : "");
    /*
     * If a PERSISTENT RESERVE OUT command with a REGISTER AND MOVE service
     * action specifies a TransportID that is the same as the initiator port
     * of the I_T nexus for the command received, then the command shall
     * be terminated with CHECK CONDITION status, with the sense key set to
     * ILLEGAL REQUEST, and the additional sense code set to INVALID FIELD
     * IN PARAMETER LIST.
     */
    pr_reg_nacl = pr_reg->pr_reg_nacl;
    matching_iname = (!strcmp(initiator_str,
                  pr_reg_nacl->initiatorname)) ? 1 : 0;
    if (!matching_iname)
        goto after_iport_check;

    if (!iport_ptr || !pr_reg->isid_present_at_reg) {
        pr_err("SPC-3 PR REGISTER_AND_MOVE: TransportID: %s"
            " matches: %s on received I_T Nexus\n", initiator_str,
            pr_reg_nacl->initiatorname);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }
    if (!strcmp(iport_ptr, pr_reg->pr_reg_isid)) {
        pr_err("SPC-3 PR REGISTER_AND_MOVE: TransportID: %s %s"
            " matches: %s %s on received I_T Nexus\n",
            initiator_str, iport_ptr, pr_reg_nacl->initiatorname,
            pr_reg->pr_reg_isid);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }
after_iport_check:
    /*
     * Locate the destination struct se_node_acl from the received Transport ID
     */
    spin_lock_irq(&dest_se_tpg->acl_node_lock);
    dest_node_acl = __core_tpg_get_initiator_node_acl(dest_se_tpg,
                initiator_str);
    if (dest_node_acl) {
        atomic_inc(&dest_node_acl->acl_pr_ref_count);
        smp_mb__after_atomic_inc();
    }
    spin_unlock_irq(&dest_se_tpg->acl_node_lock);

    if (!dest_node_acl) {
        pr_err("Unable to locate %s dest_node_acl for"
            " TransportID%s\n", dest_tf_ops->get_fabric_name(),
            initiator_str);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }
    ret = core_scsi3_nodeacl_depend_item(dest_node_acl);
    if (ret != 0) {
        pr_err("core_scsi3_nodeacl_depend_item() for"
            " dest_node_acl\n");
        atomic_dec(&dest_node_acl->acl_pr_ref_count);
        smp_mb__after_atomic_dec();
        dest_node_acl = NULL;
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }

    pr_debug("SPC-3 PR REGISTER_AND_MOVE: Found %s dest_node_acl:"
        " %s from TransportID\n", dest_tf_ops->get_fabric_name(),
        dest_node_acl->initiatorname);

    /*
     * Locate the struct se_dev_entry pointer for the matching RELATIVE TARGET
     * PORT IDENTIFIER.
     */
    dest_se_deve = core_get_se_deve_from_rtpi(dest_node_acl, rtpi);
    if (!dest_se_deve) {
        pr_err("Unable to locate %s dest_se_deve from RTPI:"
            " %hu\n",  dest_tf_ops->get_fabric_name(), rtpi);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }

    ret = core_scsi3_lunacl_depend_item(dest_se_deve);
    if (ret < 0) {
        pr_err("core_scsi3_lunacl_depend_item() failed\n");
        atomic_dec(&dest_se_deve->pr_ref_count);
        smp_mb__after_atomic_dec();
        dest_se_deve = NULL;
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        ret = -EINVAL;
        goto out;
    }

    pr_debug("SPC-3 PR REGISTER_AND_MOVE: Located %s node %s LUN"
        " ACL for dest_se_deve->mapped_lun: %u\n",
        dest_tf_ops->get_fabric_name(), dest_node_acl->initiatorname,
        dest_se_deve->mapped_lun);

    /*
     * A persistent reservation needs to already existing in order to
     * successfully complete the REGISTER_AND_MOVE service action..
     */
    spin_lock(&dev->dev_reservation_lock);
    pr_res_holder = dev->dev_pr_res_holder;
    if (!pr_res_holder) {
        pr_warn("SPC-3 PR REGISTER_AND_MOVE: No reservation"
            " currently held\n");
        spin_unlock(&dev->dev_reservation_lock);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        ret = -EINVAL;
        goto out;
    }
    /*
     * The received on I_T Nexus must be the reservation holder.
     *
     * From spc4r17 section 5.7.8  Table 50 --
     *  Register behaviors for a REGISTER AND MOVE service action
     */
    if (pr_res_holder != pr_reg) {
        pr_warn("SPC-3 PR REGISTER_AND_MOVE: Calling I_T"
            " Nexus is not reservation holder\n");
        spin_unlock(&dev->dev_reservation_lock);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        ret = -EINVAL;
        goto out;
    }
    /*
     * From spc4r17 section 5.7.8: registering and moving reservation
     *
     * If a PERSISTENT RESERVE OUT command with a REGISTER AND MOVE service
     * action is received and the established persistent reservation is a
     * Write Exclusive - All Registrants type or Exclusive Access -
     * All Registrants type reservation, then the command shall be completed
     * with RESERVATION CONFLICT status.
     */
    if ((pr_res_holder->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG) ||
        (pr_res_holder->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG)) {
        pr_warn("SPC-3 PR REGISTER_AND_MOVE: Unable to move"
            " reservation for type: %s\n",
            core_scsi3_pr_dump_type(pr_res_holder->pr_res_type));
        spin_unlock(&dev->dev_reservation_lock);
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        ret = -EINVAL;
        goto out;
    }
    pr_res_nacl = pr_res_holder->pr_reg_nacl;
    /*
     * b) Ignore the contents of the (received) SCOPE and TYPE fields;
     */
    type = pr_res_holder->pr_res_type;
    scope = pr_res_holder->pr_res_type;
    /*
     * c) Associate the reservation key specified in the SERVICE ACTION
     *    RESERVATION KEY field with the I_T nexus specified as the
     *    destination of the register and move, where:
     *    A) The I_T nexus is specified by the TransportID and the
     *   RELATIVE TARGET PORT IDENTIFIER field (see 6.14.4); and
     *    B) Regardless of the TransportID format used, the association for
     *       the initiator port is based on either the initiator port name
     *       (see 3.1.71) on SCSI transport protocols where port names are
     *       required or the initiator port identifier (see 3.1.70) on SCSI
     *       transport protocols where port names are not required;
     * d) Register the reservation key specified in the SERVICE ACTION
     *    RESERVATION KEY field;
     * e) Retain the reservation key specified in the SERVICE ACTION
     *    RESERVATION KEY field and associated information;
     *
     * Also, It is not an error for a REGISTER AND MOVE service action to
     * register an I_T nexus that is already registered with the same
     * reservation key or a different reservation key.
     */
    dest_pr_reg = __core_scsi3_locate_pr_reg(dev, dest_node_acl,
                    iport_ptr);
    if (!dest_pr_reg) {
        ret = core_scsi3_alloc_registration(cmd->se_dev,
                dest_node_acl, dest_se_deve, iport_ptr,
                sa_res_key, 0, aptpl, 2, 1);
        if (ret != 0) {
            spin_unlock(&dev->dev_reservation_lock);
            cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
            ret = -EINVAL;
            goto out;
        }
        dest_pr_reg = __core_scsi3_locate_pr_reg(dev, dest_node_acl,
                        iport_ptr);
        new_reg = 1;
    }
    /*
     * f) Release the persistent reservation for the persistent reservation
     *    holder (i.e., the I_T nexus on which the
     */
    __core_scsi3_complete_pro_release(dev, pr_res_nacl,
            dev->dev_pr_res_holder, 0);
    /*
     * g) Move the persistent reservation to the specified I_T nexus using
     *    the same scope and type as the persistent reservation released in
     *    item f); and
     */
    dev->dev_pr_res_holder = dest_pr_reg;
    dest_pr_reg->pr_res_holder = 1;
    dest_pr_reg->pr_res_type = type;
    pr_reg->pr_res_scope = scope;
    prf_isid = core_pr_dump_initiator_port(pr_reg, &i_buf[0],
                PR_REG_ISID_ID_LEN);
    /*
     * Increment PRGeneration for existing registrations..
     */
    if (!new_reg)
        dest_pr_reg->pr_res_generation = pr_tmpl->pr_generation++;
    spin_unlock(&dev->dev_reservation_lock);

    pr_debug("SPC-3 PR [%s] Service Action: REGISTER_AND_MOVE"
        " created new reservation holder TYPE: %s on object RTPI:"
        " %hu  PRGeneration: 0x%08x\n", dest_tf_ops->get_fabric_name(),
        core_scsi3_pr_dump_type(type), rtpi,
        dest_pr_reg->pr_res_generation);
    pr_debug("SPC-3 PR Successfully moved reservation from"
        " %s Fabric Node: %s%s -> %s Fabric Node: %s %s\n",
        tf_ops->get_fabric_name(), pr_reg_nacl->initiatorname,
        (prf_isid) ? &i_buf[0] : "", dest_tf_ops->get_fabric_name(),
        dest_node_acl->initiatorname, (iport_ptr != NULL) ?
        iport_ptr : "");
    /*
     * It is now safe to release configfs group dependencies for destination
     * of Transport ID Initiator Device/Port Identifier
     */
    core_scsi3_lunacl_undepend_item(dest_se_deve);
    core_scsi3_nodeacl_undepend_item(dest_node_acl);
    core_scsi3_tpg_undepend_item(dest_se_tpg);
    /*
     * h) If the UNREG bit is set to one, unregister (see 5.7.11.3) the I_T
     * nexus on which PERSISTENT RESERVE OUT command was received.
     */
    if (unreg) {
        spin_lock(&pr_tmpl->registration_lock);
        __core_scsi3_free_registration(dev, pr_reg, NULL, 1);
        spin_unlock(&pr_tmpl->registration_lock);
    } else
        core_scsi3_put_pr_reg(pr_reg);

    /*
     * Clear the APTPL metadata if APTPL has been disabled, otherwise
     * write out the updated metadata to struct file for this SCSI device.
     */
    if (!aptpl) {
        pr_tmpl->pr_aptpl_active = 0;
        core_scsi3_update_and_write_aptpl(cmd->se_dev, NULL, 0);
        pr_debug("SPC-3 PR: Set APTPL Bit Deactivated for"
                " REGISTER_AND_MOVE\n");
    } else {
        pr_tmpl->pr_aptpl_active = 1;
        ret = core_scsi3_update_and_write_aptpl(cmd->se_dev,
                &dest_pr_reg->pr_aptpl_buf[0],
                pr_tmpl->pr_aptpl_buf_len);
        if (!ret)
            pr_debug("SPC-3 PR: Set APTPL Bit Activated for"
                    " REGISTER_AND_MOVE\n");
    }

    transport_kunmap_data_sg(cmd);

    core_scsi3_put_pr_reg(dest_pr_reg);
    return 0;
out:
    if (buf)
        transport_kunmap_data_sg(cmd);
    if (dest_se_deve)
        core_scsi3_lunacl_undepend_item(dest_se_deve);
    if (dest_node_acl)
        core_scsi3_nodeacl_undepend_item(dest_node_acl);
    core_scsi3_tpg_undepend_item(dest_se_tpg);
    core_scsi3_put_pr_reg(pr_reg);
    return ret;
}

static unsigned long long core_scsi3_extract_reservation_key(unsigned char *cdb)
{
    unsigned int __v1, __v2;

    __v1 = (cdb[0] << 24) | (cdb[1] << 16) | (cdb[2] << 8) | cdb[3];
    __v2 = (cdb[4] << 24) | (cdb[5] << 16) | (cdb[6] << 8) | cdb[7];

    return ((unsigned long long)__v2) | (unsigned long long)__v1 << 32;
}

/*
 * See spc4r17 section 6.14 Table 170
 */
int target_scsi3_emulate_pr_out(struct se_cmd *cmd)
{
    unsigned char *cdb = &cmd->t_task_cdb[0];
    unsigned char *buf;
    u64 res_key, sa_res_key;
    int sa, scope, type, aptpl;
    int spec_i_pt = 0, all_tg_pt = 0, unreg = 0;
    int ret;

    /*
     * Following spc2r20 5.5.1 Reservations overview:
     *
     * If a logical unit has been reserved by any RESERVE command and is
     * still reserved by any initiator, all PERSISTENT RESERVE IN and all
     * PERSISTENT RESERVE OUT commands shall conflict regardless of
     * initiator or service action and shall terminate with a RESERVATION
     * CONFLICT status.
     */
    if (cmd->se_dev->dev_flags & DF_SPC2_RESERVATIONS) {
        pr_err("Received PERSISTENT_RESERVE CDB while legacy"
            " SPC-2 reservation is held, returning"
            " RESERVATION_CONFLICT\n");
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        ret = -EINVAL;
        goto out;
    }

    /*
     * FIXME: A NULL struct se_session pointer means an this is not coming from
     * a $FABRIC_MOD's nexus, but from internal passthrough ops.
     */
    if (!cmd->se_sess) {
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        ret = -EINVAL;
        goto out;
    }

    if (cmd->data_length < 24) {
        pr_warn("SPC-PR: Received PR OUT parameter list"
            " length too small: %u\n", cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }
    /*
     * From the PERSISTENT_RESERVE_OUT command descriptor block (CDB)
     */
    sa = (cdb[1] & 0x1f);
    scope = (cdb[2] & 0xf0);
    type = (cdb[2] & 0x0f);

    buf = transport_kmap_data_sg(cmd);
    /*
     * From PERSISTENT_RESERVE_OUT parameter list (payload)
     */
    res_key = core_scsi3_extract_reservation_key(&buf[0]);
    sa_res_key = core_scsi3_extract_reservation_key(&buf[8]);
    /*
     * REGISTER_AND_MOVE uses a different SA parameter list containing
     * SCSI TransportIDs.
     */
    if (sa != PRO_REGISTER_AND_MOVE) {
        spec_i_pt = (buf[20] & 0x08);
        all_tg_pt = (buf[20] & 0x04);
        aptpl = (buf[20] & 0x01);
    } else {
        aptpl = (buf[17] & 0x01);
        unreg = (buf[17] & 0x02);
    }
    transport_kunmap_data_sg(cmd);
    buf = NULL;

    /*
     * SPEC_I_PT=1 is only valid for Service action: REGISTER
     */
    if (spec_i_pt && ((cdb[1] & 0x1f) != PRO_REGISTER)) {
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }

    /*
     * From spc4r17 section 6.14:
     *
     * If the SPEC_I_PT bit is set to zero, the service action is not
     * REGISTER AND MOVE, and the parameter list length is not 24, then
     * the command shall be terminated with CHECK CONDITION status, with
     * the sense key set to ILLEGAL REQUEST, and the additional sense
     * code set to PARAMETER LIST LENGTH ERROR.
     */
    if (!spec_i_pt && ((cdb[1] & 0x1f) != PRO_REGISTER_AND_MOVE) &&
        (cmd->data_length != 24)) {
        pr_warn("SPC-PR: Received PR OUT illegal parameter"
            " list length: %u\n", cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
        ret = -EINVAL;
        goto out;
    }
    /*
     * (core_scsi3_emulate_pro_* function parameters
     * are defined by spc4r17 Table 174:
     * PERSISTENT_RESERVE_OUT service actions and valid parameters.
     */
    switch (sa) {
    case PRO_REGISTER:
        ret = core_scsi3_emulate_pro_register(cmd,
            res_key, sa_res_key, aptpl, all_tg_pt, spec_i_pt, 0);
        break;
    case PRO_RESERVE:
        ret = core_scsi3_emulate_pro_reserve(cmd, type, scope, res_key);
        break;
    case PRO_RELEASE:
        ret = core_scsi3_emulate_pro_release(cmd, type, scope, res_key);
        break;
    case PRO_CLEAR:
        ret = core_scsi3_emulate_pro_clear(cmd, res_key);
        break;
    case PRO_PREEMPT:
        ret = core_scsi3_emulate_pro_preempt(cmd, type, scope,
                    res_key, sa_res_key, 0);
        break;
    case PRO_PREEMPT_AND_ABORT:
        ret = core_scsi3_emulate_pro_preempt(cmd, type, scope,
                    res_key, sa_res_key, 1);
        break;
    case PRO_REGISTER_AND_IGNORE_EXISTING_KEY:
        ret = core_scsi3_emulate_pro_register(cmd,
            0, sa_res_key, aptpl, all_tg_pt, spec_i_pt, 1);
        break;
    case PRO_REGISTER_AND_MOVE:
        ret = core_scsi3_emulate_pro_register_and_move(cmd, res_key,
                sa_res_key, aptpl, unreg);
        break;
    default:
        pr_err("Unknown PERSISTENT_RESERVE_OUT service"
            " action: 0x%02x\n", cdb[1] & 0x1f);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        ret = -EINVAL;
        break;
    }

out:
    if (!ret)
        target_complete_cmd(cmd, GOOD);
    return ret;
}

/*
 * PERSISTENT_RESERVE_IN Service Action READ_KEYS
 *
 * See spc4r17 section 5.7.6.2 and section 6.13.2, Table 160
 */
static int core_scsi3_pri_read_keys(struct se_cmd *cmd)
{
    struct se_device *se_dev = cmd->se_dev;
    struct se_subsystem_dev *su_dev = se_dev->se_sub_dev;
    struct t10_pr_registration *pr_reg;
    unsigned char *buf;
    u32 add_len = 0, off = 8;

    if (cmd->data_length < 8) {
        pr_err("PRIN SA READ_KEYS SCSI Data Length: %u"
            " too small\n", cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        return -EINVAL;
    }

    buf = transport_kmap_data_sg(cmd);
    buf[0] = ((su_dev->t10_pr.pr_generation >> 24) & 0xff);
    buf[1] = ((su_dev->t10_pr.pr_generation >> 16) & 0xff);
    buf[2] = ((su_dev->t10_pr.pr_generation >> 8) & 0xff);
    buf[3] = (su_dev->t10_pr.pr_generation & 0xff);

    spin_lock(&su_dev->t10_pr.registration_lock);
    list_for_each_entry(pr_reg, &su_dev->t10_pr.registration_list,
            pr_reg_list) {
        /*
         * Check for overflow of 8byte PRI READ_KEYS payload and
         * next reservation key list descriptor.
         */
        if ((add_len + 8) > (cmd->data_length - 8))
            break;

        buf[off++] = ((pr_reg->pr_res_key >> 56) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 48) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 40) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 32) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 24) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 16) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 8) & 0xff);
        buf[off++] = (pr_reg->pr_res_key & 0xff);

        add_len += 8;
    }
    spin_unlock(&su_dev->t10_pr.registration_lock);

    buf[4] = ((add_len >> 24) & 0xff);
    buf[5] = ((add_len >> 16) & 0xff);
    buf[6] = ((add_len >> 8) & 0xff);
    buf[7] = (add_len & 0xff);

    transport_kunmap_data_sg(cmd);

    return 0;
}

/*
 * PERSISTENT_RESERVE_IN Service Action READ_RESERVATION
 *
 * See spc4r17 section 5.7.6.3 and section 6.13.3.2 Table 161 and 162
 */
static int core_scsi3_pri_read_reservation(struct se_cmd *cmd)
{
    struct se_device *se_dev = cmd->se_dev;
    struct se_subsystem_dev *su_dev = se_dev->se_sub_dev;
    struct t10_pr_registration *pr_reg;
    unsigned char *buf;
    u64 pr_res_key;
    u32 add_len = 16; /* Hardcoded to 16 when a reservation is held. */

    if (cmd->data_length < 8) {
        pr_err("PRIN SA READ_RESERVATIONS SCSI Data Length: %u"
            " too small\n", cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        return -EINVAL;
    }

    buf = transport_kmap_data_sg(cmd);
    buf[0] = ((su_dev->t10_pr.pr_generation >> 24) & 0xff);
    buf[1] = ((su_dev->t10_pr.pr_generation >> 16) & 0xff);
    buf[2] = ((su_dev->t10_pr.pr_generation >> 8) & 0xff);
    buf[3] = (su_dev->t10_pr.pr_generation & 0xff);

    spin_lock(&se_dev->dev_reservation_lock);
    pr_reg = se_dev->dev_pr_res_holder;
    if (pr_reg) {
        /*
         * Set the hardcoded Additional Length
         */
        buf[4] = ((add_len >> 24) & 0xff);
        buf[5] = ((add_len >> 16) & 0xff);
        buf[6] = ((add_len >> 8) & 0xff);
        buf[7] = (add_len & 0xff);

        if (cmd->data_length < 22)
            goto err;

        /*
         * Set the Reservation key.
         *
         * From spc4r17, section 5.7.10:
         * A persistent reservation holder has its reservation key
         * returned in the parameter data from a PERSISTENT
         * RESERVE IN command with READ RESERVATION service action as
         * follows:
         * a) For a persistent reservation of the type Write Exclusive
         *    - All Registrants or Exclusive Access ­ All Regitrants,
         *      the reservation key shall be set to zero; or
         * b) For all other persistent reservation types, the
         *    reservation key shall be set to the registered
         *    reservation key for the I_T nexus that holds the
         *    persistent reservation.
         */
        if ((pr_reg->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG) ||
            (pr_reg->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG))
            pr_res_key = 0;
        else
            pr_res_key = pr_reg->pr_res_key;

        buf[8] = ((pr_res_key >> 56) & 0xff);
        buf[9] = ((pr_res_key >> 48) & 0xff);
        buf[10] = ((pr_res_key >> 40) & 0xff);
        buf[11] = ((pr_res_key >> 32) & 0xff);
        buf[12] = ((pr_res_key >> 24) & 0xff);
        buf[13] = ((pr_res_key >> 16) & 0xff);
        buf[14] = ((pr_res_key >> 8) & 0xff);
        buf[15] = (pr_res_key & 0xff);
        /*
         * Set the SCOPE and TYPE
         */
        buf[21] = (pr_reg->pr_res_scope & 0xf0) |
              (pr_reg->pr_res_type & 0x0f);
    }

err:
    spin_unlock(&se_dev->dev_reservation_lock);
    transport_kunmap_data_sg(cmd);

    return 0;
}

/*
 * PERSISTENT_RESERVE_IN Service Action REPORT_CAPABILITIES
 *
 * See spc4r17 section 6.13.4 Table 165
 */
static int core_scsi3_pri_report_capabilities(struct se_cmd *cmd)
{
    struct se_device *dev = cmd->se_dev;
    struct t10_reservation *pr_tmpl = &dev->se_sub_dev->t10_pr;
    unsigned char *buf;
    u16 add_len = 8; /* Hardcoded to 8. */

    if (cmd->data_length < 6) {
        pr_err("PRIN SA REPORT_CAPABILITIES SCSI Data Length:"
            " %u too small\n", cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        return -EINVAL;
    }

    buf = transport_kmap_data_sg(cmd);

    buf[0] = ((add_len << 8) & 0xff);
    buf[1] = (add_len & 0xff);
    buf[2] |= 0x10; /* CRH: Compatible Reservation Hanlding bit. */
    buf[2] |= 0x08; /* SIP_C: Specify Initiator Ports Capable bit */
    buf[2] |= 0x04; /* ATP_C: All Target Ports Capable bit */
    buf[2] |= 0x01; /* PTPL_C: Persistence across Target Power Loss bit */
    /*
     * We are filling in the PERSISTENT RESERVATION TYPE MASK below, so
     * set the TMV: Task Mask Valid bit.
     */
    buf[3] |= 0x80;
    /*
     * Change ALLOW COMMANDs to 0x20 or 0x40 later from Table 166
     */
    buf[3] |= 0x10; /* ALLOW COMMANDs field 001b */
    /*
     * PTPL_A: Persistence across Target Power Loss Active bit
     */
    if (pr_tmpl->pr_aptpl_active)
        buf[3] |= 0x01;
    /*
     * Setup the PERSISTENT RESERVATION TYPE MASK from Table 167
     */
    buf[4] |= 0x80; /* PR_TYPE_EXCLUSIVE_ACCESS_ALLREG */
    buf[4] |= 0x40; /* PR_TYPE_EXCLUSIVE_ACCESS_REGONLY */
    buf[4] |= 0x20; /* PR_TYPE_WRITE_EXCLUSIVE_REGONLY */
    buf[4] |= 0x08; /* PR_TYPE_EXCLUSIVE_ACCESS */
    buf[4] |= 0x02; /* PR_TYPE_WRITE_EXCLUSIVE */
    buf[5] |= 0x01; /* PR_TYPE_EXCLUSIVE_ACCESS_ALLREG */

    transport_kunmap_data_sg(cmd);

    return 0;
}

/*
 * PERSISTENT_RESERVE_IN Service Action READ_FULL_STATUS
 *
 * See spc4r17 section 6.13.5 Table 168 and 169
 */
static int core_scsi3_pri_read_full_status(struct se_cmd *cmd)
{
    struct se_device *se_dev = cmd->se_dev;
    struct se_node_acl *se_nacl;
    struct se_subsystem_dev *su_dev = se_dev->se_sub_dev;
    struct se_portal_group *se_tpg;
    struct t10_pr_registration *pr_reg, *pr_reg_tmp;
    struct t10_reservation *pr_tmpl = &se_dev->se_sub_dev->t10_pr;
    unsigned char *buf;
    u32 add_desc_len = 0, add_len = 0, desc_len, exp_desc_len;
    u32 off = 8; /* off into first Full Status descriptor */
    int format_code = 0;

    if (cmd->data_length < 8) {
        pr_err("PRIN SA READ_FULL_STATUS SCSI Data Length: %u"
            " too small\n", cmd->data_length);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        return -EINVAL;
    }

    buf = transport_kmap_data_sg(cmd);

    buf[0] = ((su_dev->t10_pr.pr_generation >> 24) & 0xff);
    buf[1] = ((su_dev->t10_pr.pr_generation >> 16) & 0xff);
    buf[2] = ((su_dev->t10_pr.pr_generation >> 8) & 0xff);
    buf[3] = (su_dev->t10_pr.pr_generation & 0xff);

    spin_lock(&pr_tmpl->registration_lock);
    list_for_each_entry_safe(pr_reg, pr_reg_tmp,
            &pr_tmpl->registration_list, pr_reg_list) {

        se_nacl = pr_reg->pr_reg_nacl;
        se_tpg = pr_reg->pr_reg_nacl->se_tpg;
        add_desc_len = 0;

        atomic_inc(&pr_reg->pr_res_holders);
        smp_mb__after_atomic_inc();
        spin_unlock(&pr_tmpl->registration_lock);
        /*
         * Determine expected length of $FABRIC_MOD specific
         * TransportID full status descriptor..
         */
        exp_desc_len = se_tpg->se_tpg_tfo->tpg_get_pr_transport_id_len(
                se_tpg, se_nacl, pr_reg, &format_code);

        if ((exp_desc_len + add_len) > cmd->data_length) {
            pr_warn("SPC-3 PRIN READ_FULL_STATUS ran"
                " out of buffer: %d\n", cmd->data_length);
            spin_lock(&pr_tmpl->registration_lock);
            atomic_dec(&pr_reg->pr_res_holders);
            smp_mb__after_atomic_dec();
            break;
        }
        /*
         * Set RESERVATION KEY
         */
        buf[off++] = ((pr_reg->pr_res_key >> 56) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 48) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 40) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 32) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 24) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 16) & 0xff);
        buf[off++] = ((pr_reg->pr_res_key >> 8) & 0xff);
        buf[off++] = (pr_reg->pr_res_key & 0xff);
        off += 4; /* Skip Over Reserved area */

        /*
         * Set ALL_TG_PT bit if PROUT SA REGISTER had this set.
         */
        if (pr_reg->pr_reg_all_tg_pt)
            buf[off] = 0x02;
        /*
         * The struct se_lun pointer will be present for the
         * reservation holder for PR_HOLDER bit.
         *
         * Also, if this registration is the reservation
         * holder, fill in SCOPE and TYPE in the next byte.
         */
        if (pr_reg->pr_res_holder) {
            buf[off++] |= 0x01;
            buf[off++] = (pr_reg->pr_res_scope & 0xf0) |
                     (pr_reg->pr_res_type & 0x0f);
        } else
            off += 2;

        off += 4; /* Skip over reserved area */
        /*
         * From spc4r17 6.3.15:
         *
         * If the ALL_TG_PT bit set to zero, the RELATIVE TARGET PORT
         * IDENTIFIER field contains the relative port identifier (see
         * 3.1.120) of the target port that is part of the I_T nexus
         * described by this full status descriptor. If the ALL_TG_PT
         * bit is set to one, the contents of the RELATIVE TARGET PORT
         * IDENTIFIER field are not defined by this standard.
         */
        if (!pr_reg->pr_reg_all_tg_pt) {
            struct se_port *port = pr_reg->pr_reg_tg_pt_lun->lun_sep;

            buf[off++] = ((port->sep_rtpi >> 8) & 0xff);
            buf[off++] = (port->sep_rtpi & 0xff);
        } else
            off += 2; /* Skip over RELATIVE TARGET PORT IDENTIFIER */

        /*
         * Now, have the $FABRIC_MOD fill in the protocol identifier
         */
        desc_len = se_tpg->se_tpg_tfo->tpg_get_pr_transport_id(se_tpg,
                se_nacl, pr_reg, &format_code, &buf[off+4]);

        spin_lock(&pr_tmpl->registration_lock);
        atomic_dec(&pr_reg->pr_res_holders);
        smp_mb__after_atomic_dec();
        /*
         * Set the ADDITIONAL DESCRIPTOR LENGTH
         */
        buf[off++] = ((desc_len >> 24) & 0xff);
        buf[off++] = ((desc_len >> 16) & 0xff);
        buf[off++] = ((desc_len >> 8) & 0xff);
        buf[off++] = (desc_len & 0xff);
        /*
         * Size of full desctipor header minus TransportID
         * containing $FABRIC_MOD specific) initiator device/port
         * WWN information.
         *
         *  See spc4r17 Section 6.13.5 Table 169
         */
        add_desc_len = (24 + desc_len);

        off += desc_len;
        add_len += add_desc_len;
    }
    spin_unlock(&pr_tmpl->registration_lock);
    /*
     * Set ADDITIONAL_LENGTH
     */
    buf[4] = ((add_len >> 24) & 0xff);
    buf[5] = ((add_len >> 16) & 0xff);
    buf[6] = ((add_len >> 8) & 0xff);
    buf[7] = (add_len & 0xff);

    transport_kunmap_data_sg(cmd);

    return 0;
}

int target_scsi3_emulate_pr_in(struct se_cmd *cmd)
{
    int ret;

    /*
     * Following spc2r20 5.5.1 Reservations overview:
     *
     * If a logical unit has been reserved by any RESERVE command and is
     * still reserved by any initiator, all PERSISTENT RESERVE IN and all
     * PERSISTENT RESERVE OUT commands shall conflict regardless of
     * initiator or service action and shall terminate with a RESERVATION
     * CONFLICT status.
     */
    if (cmd->se_dev->dev_flags & DF_SPC2_RESERVATIONS) {
        pr_err("Received PERSISTENT_RESERVE CDB while legacy"
            " SPC-2 reservation is held, returning"
            " RESERVATION_CONFLICT\n");
        cmd->scsi_sense_reason = TCM_RESERVATION_CONFLICT;
        return -EINVAL;
    }

    switch (cmd->t_task_cdb[1] & 0x1f) {
    case PRI_READ_KEYS:
        ret = core_scsi3_pri_read_keys(cmd);
        break;
    case PRI_READ_RESERVATION:
        ret = core_scsi3_pri_read_reservation(cmd);
        break;
    case PRI_REPORT_CAPABILITIES:
        ret = core_scsi3_pri_report_capabilities(cmd);
        break;
    case PRI_READ_FULL_STATUS:
        ret = core_scsi3_pri_read_full_status(cmd);
        break;
    default:
        pr_err("Unknown PERSISTENT_RESERVE_IN service"
            " action: 0x%02x\n", cmd->t_task_cdb[1] & 0x1f);
        cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
        ret = -EINVAL;
        break;
    }

    if (!ret)
        target_complete_cmd(cmd, GOOD);
    return ret;
}

static int core_pt_reservation_check(struct se_cmd *cmd, u32 *pr_res_type)
{
    return 0;
}

static int core_pt_seq_non_holder(
    struct se_cmd *cmd,
    unsigned char *cdb,
    u32 pr_reg_type)
{
    return 0;
}

int core_setup_reservations(struct se_device *dev, int force_pt)
{
    struct se_subsystem_dev *su_dev = dev->se_sub_dev;
    struct t10_reservation *rest = &su_dev->t10_pr;
    /*
     * If this device is from Target_Core_Mod/pSCSI, use the reservations
     * of the Underlying SCSI hardware.  In Linux/SCSI terms, this can
     * cause a problem because libata and some SATA RAID HBAs appear
     * under Linux/SCSI, but to emulate reservations themselves.
     */
    if (((dev->transport->transport_type == TRANSPORT_PLUGIN_PHBA_PDEV) &&
        !(dev->se_sub_dev->se_dev_attrib.emulate_reservations)) || force_pt) {
        rest->res_type = SPC_PASSTHROUGH;
        rest->pr_ops.t10_reservation_check = &core_pt_reservation_check;
        rest->pr_ops.t10_seq_non_holder = &core_pt_seq_non_holder;
        pr_debug("%s: Using SPC_PASSTHROUGH, no reservation"
            " emulation\n", dev->transport->name);
        return 0;
    }
    /*
     * If SPC-3 or above is reported by real or emulated struct se_device,
     * use emulated Persistent Reservations.
     */
    if (dev->transport->get_device_rev(dev) >= SCSI_3) {
        rest->res_type = SPC3_PERSISTENT_RESERVATIONS;
        rest->pr_ops.t10_reservation_check = &core_scsi3_pr_reservation_check;
        rest->pr_ops.t10_seq_non_holder = &core_scsi3_pr_seq_non_holder;
        pr_debug("%s: Using SPC3_PERSISTENT_RESERVATIONS"
            " emulation\n", dev->transport->name);
    } else {
        rest->res_type = SPC2_RESERVATIONS;
        rest->pr_ops.t10_reservation_check = &core_scsi2_reservation_check;
        rest->pr_ops.t10_seq_non_holder =
                &core_scsi2_reservation_seq_non_holder;
        pr_debug("%s: Using SPC2_RESERVATIONS emulation\n",
            dev->transport->name);
    }

    return 0;
}