// SPDX-License-Identifier: GPL-2.0-or-later
/*******************************************************************************
 * Filename:  target_core_pr.c
 *
 * This file contains SPC-3 compliant persistent reservations and
 * legacy SPC-2 reservations with compatible reservation handling (CRH=1)
 *
 * (c) Copyright 2009-2013 Datera, Inc.
 *
 * Nicholas A. Bellinger <nab@kernel.org>
 *
 ******************************************************************************/

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/file.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <scsi/scsi_proto.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_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 {
        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;
};

void core_pr_dump_initiator_port(
        struct t10_pr_registration *pr_reg,
        char *buf,
        u32 size)
{
        if (!pr_reg->isid_present_at_reg) {
                buf[0] = '\0';
                return;
        }

        snprintf(buf, size, ",i,0x%s", pr_reg->pr_reg_isid);
}

enum register_type {
        REGISTER,
        REGISTER_AND_IGNORE_EXISTING_KEY,
        REGISTER_AND_MOVE,
};

enum preempt_type {
        PREEMPT,
        PREEMPT_AND_ABORT,
};

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

static int is_reservation_holder(
        struct t10_pr_registration *pr_res_holder,
        struct t10_pr_registration *pr_reg)
{
        int pr_res_type;

        if (pr_res_holder) {
                pr_res_type = pr_res_holder->pr_res_type;

                return pr_res_holder == pr_reg ||
                       pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG ||
                       pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG;
        }
        return 0;
}

static sense_reason_t
target_scsi2_reservation_check(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct se_session *sess = cmd->se_sess;

        switch (cmd->t_task_cdb[0]) {
        case INQUIRY:
        case RELEASE:
        case RELEASE_10:
                return 0;
        default:
                break;
        }

        if (!dev->reservation_holder || !sess)
                return 0;

        if (dev->reservation_holder->se_node_acl != sess->se_node_acl)
                return TCM_RESERVATION_CONFLICT;

        if (dev->dev_reservation_flags & DRF_SPC2_RESERVATIONS_WITH_ISID) {
                if (dev->dev_res_bin_isid != sess->sess_bin_isid)
                        return TCM_RESERVATION_CONFLICT;
        }

        return 0;
}

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_device *dev = cmd->se_dev;
        struct t10_pr_registration *pr_reg;
        struct t10_reservation *pr_tmpl = &dev->t10_pr;
        int conflict = 0;

        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");
                return -EBUSY;
        }

        return 0;
}

void target_release_reservation(struct se_device *dev)
{
        dev->reservation_holder = NULL;
        dev->dev_reservation_flags &= ~DRF_SPC2_RESERVATIONS;
        if (dev->dev_reservation_flags & DRF_SPC2_RESERVATIONS_WITH_ISID) {
                dev->dev_res_bin_isid = 0;
                dev->dev_reservation_flags &= ~DRF_SPC2_RESERVATIONS_WITH_ISID;
        }
}

sense_reason_t
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 rc;

        if (!sess || !sess->se_tpg)
                goto out;
        rc = target_check_scsi2_reservation_conflict(cmd);
        if (rc == 1)
                goto out;
        if (rc < 0)
                return TCM_RESERVATION_CONFLICT;

        spin_lock(&dev->dev_reservation_lock);
        if (!dev->reservation_holder || !sess)
                goto out_unlock;

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

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

        target_release_reservation(dev);
        tpg = sess->se_tpg;
        pr_debug("SCSI-2 Released reservation for %s LUN: %llu ->"
                " MAPPED LUN: %llu for %s\n",
                tpg->se_tpg_tfo->fabric_name,
                cmd->se_lun->unpacked_lun, cmd->orig_fe_lun,
                sess->se_node_acl->initiatorname);

out_unlock:
        spin_unlock(&dev->dev_reservation_lock);
out:
        target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
}

sense_reason_t
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;
        sense_reason_t ret = 0;
        int rc;

        if ((cmd->t_task_cdb[1] & 0x01) &&
            (cmd->t_task_cdb[1] & 0x02)) {
                pr_err("LongIO and Obsolete Bits set, returning ILLEGAL_REQUEST\n");
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }
        /*
         * 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;

        if (rc < 0)
                return TCM_RESERVATION_CONFLICT;

        tpg = sess->se_tpg;
        spin_lock(&dev->dev_reservation_lock);
        if (dev->reservation_holder &&
            dev->reservation_holder->se_node_acl != sess->se_node_acl) {
                pr_err("SCSI-2 RESERVATION CONFLICT for %s fabric\n",
                        tpg->se_tpg_tfo->fabric_name);
                pr_err("Original reserver LUN: %llu %s\n",
                        cmd->se_lun->unpacked_lun,
                        dev->reservation_holder->se_node_acl->initiatorname);
                pr_err("Current attempt - LUN: %llu -> MAPPED LUN: %llu"
                        " from %s \n", cmd->se_lun->unpacked_lun,
                        cmd->orig_fe_lun,
                        sess->se_node_acl->initiatorname);
                ret = TCM_RESERVATION_CONFLICT;
                goto out_unlock;
        }

        dev->reservation_holder = sess;
        dev->dev_reservation_flags |= DRF_SPC2_RESERVATIONS;
        if (sess->sess_bin_isid != 0) {
                dev->dev_res_bin_isid = sess->sess_bin_isid;
                dev->dev_reservation_flags |= DRF_SPC2_RESERVATIONS_WITH_ISID;
        }
        pr_debug("SCSI-2 Reserved %s LUN: %llu -> MAPPED LUN: %llu"
                " for %s\n", tpg->se_tpg_tfo->fabric_name,
                cmd->se_lun->unpacked_lun, cmd->orig_fe_lun,
                sess->se_node_acl->initiatorname);

out_unlock:
        spin_unlock(&dev->dev_reservation_lock);
out:
        if (!ret)
                target_complete_cmd(cmd, SAM_STAT_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, u32 pr_reg_type,
                                        bool isid_mismatch)
{
        unsigned char *cdb = cmd->t_task_cdb;
        struct se_session *se_sess = cmd->se_sess;
        struct se_node_acl *nacl = se_sess->se_node_acl;
        int other_cdb = 0;
        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 */

        if (isid_mismatch) {
                registered_nexus = 0;
        } else {
                struct se_dev_entry *se_deve;

                rcu_read_lock();
                se_deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
                if (se_deve)
                        registered_nexus = test_bit(DEF_PR_REG_ACTIVE,
                                                    &se_deve->deve_flags);
                rcu_read_unlock();
        }

        switch (pr_reg_type) {
        case PR_TYPE_WRITE_EXCLUSIVE:
                we = 1;
                fallthrough;
        case PR_TYPE_EXCLUSIVE_ACCESS:
                /*
                 * Some commands are only allowed for the persistent reservation
                 * holder.
                 */
                break;
        case PR_TYPE_WRITE_EXCLUSIVE_REGONLY:
                we = 1;
                fallthrough;
        case PR_TYPE_EXCLUSIVE_ACCESS_REGONLY:
                /*
                 * Some commands are only allowed for registered I_T Nexuses.
                 */
                reg_only = 1;
                break;
        case PR_TYPE_WRITE_EXCLUSIVE_ALLREG:
                we = 1;
                fallthrough;
        case PR_TYPE_EXCLUSIVE_ACCESS_ALLREG:
                /*
                 * Each registered I_T Nexus is a reservation holder.
                 */
                all_reg = 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 SERVICE_ACTION_IN_12:
        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 explicit 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 implicit 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 implicit CDB: 0x%02x for %s"
                                " reservation\n", cdb[0],
                                core_scsi3_pr_dump_type(pr_reg_type));

                        return 0;
                }
       } else if (we && registered_nexus) {
               /*
                * Reads are allowed for Write Exclusive locks
                * from all registrants.
                */
               if (cmd->data_direction == DMA_FROM_DEVICE) {
                       pr_debug("Allowing READ 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 sense_reason_t
target_scsi3_pr_reservation_check(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct se_session *sess = cmd->se_sess;
        u32 pr_reg_type;
        bool isid_mismatch = false;

        if (!dev->dev_pr_res_holder)
                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)
                goto check_nonholder;

        if (dev->dev_pr_res_holder->isid_present_at_reg) {
                if (dev->dev_pr_res_holder->pr_reg_bin_isid !=
                    sess->sess_bin_isid) {
                        isid_mismatch = true;
                        goto check_nonholder;
                }
        }

        return 0;

check_nonholder:
        if (core_scsi3_pr_seq_non_holder(cmd, pr_reg_type, isid_mismatch))
                return TCM_RESERVATION_CONFLICT;
        return 0;
}

static u32 core_scsi3_pr_generation(struct se_device *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 = dev->t10_pr.pr_generation++;
        spin_unlock(&dev->dev_reservation_lock);

        return prg;
}

static struct t10_pr_registration *__core_scsi3_do_alloc_registration(
        struct se_device *dev,
        struct se_node_acl *nacl,
        struct se_lun *lun,
        struct se_dev_entry *dest_deve,
        u64 mapped_lun,
        unsigned char *isid,
        u64 sa_res_key,
        int all_tg_pt,
        int aptpl)
{
        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;
        }

        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;
        /*
         * For destination registrations for ALL_TG_PT=1 and SPEC_I_PT=1,
         * the se_dev_entry->pr_ref will have been already obtained by
         * core_get_se_deve_from_rtpi() or __core_scsi3_alloc_registration().
         *
         * Otherwise, locate se_dev_entry now and obtain a reference until
         * registration completes in __core_scsi3_add_registration().
         */
        if (dest_deve) {
                pr_reg->pr_reg_deve = dest_deve;
        } else {
                rcu_read_lock();
                pr_reg->pr_reg_deve = target_nacl_find_deve(nacl, mapped_lun);
                if (!pr_reg->pr_reg_deve) {
                        rcu_read_unlock();
                        pr_err("Unable to locate PR deve %s mapped_lun: %llu\n",
                                nacl->initiatorname, mapped_lun);
                        kmem_cache_free(t10_pr_reg_cache, pr_reg);
                        return NULL;
                }
                kref_get(&pr_reg->pr_reg_deve->pr_kref);
                rcu_read_unlock();
        }
        pr_reg->pr_res_mapped_lun = mapped_lun;
        pr_reg->pr_aptpl_target_lun = lun->unpacked_lun;
        pr_reg->tg_pt_sep_rtpi = lun->lun_rtpi;
        pr_reg->pr_res_key = sa_res_key;
        pr_reg->pr_reg_all_tg_pt = all_tg_pt;
        pr_reg->pr_reg_aptpl = aptpl;
        /*
         * 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_lun *lun,
        struct se_dev_entry *deve,
        u64 mapped_lun,
        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_lun_acl *lacl_tmp;
        struct se_lun *lun_tmp, *next, *dest_lun;
        const 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, lun, deve, mapped_lun,
                                                    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(lun_tmp, next, &dev->dev_sep_list, lun_dev_link) {
                if (!percpu_ref_tryget_live(&lun_tmp->lun_ref))
                        continue;
                spin_unlock(&dev->se_port_lock);

                spin_lock(&lun_tmp->lun_deve_lock);
                list_for_each_entry(deve_tmp, &lun_tmp->lun_deve_list, lun_link) {
                        /*
                         * This pointer will be NULL for demo mode MappedLUNs
                         * that have not been make explicit via a ConfigFS
                         * MappedLUN group for the SCSI Initiator Node ACL.
                         */
                        if (!deve_tmp->se_lun_acl)
                                continue;

                        lacl_tmp = rcu_dereference_check(deve_tmp->se_lun_acl,
                                                lockdep_is_held(&lun_tmp->lun_deve_lock));
                        nacl_tmp = lacl_tmp->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;

                        kref_get(&deve_tmp->pr_kref);
                        spin_unlock(&lun_tmp->lun_deve_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");
                                percpu_ref_put(&lun_tmp->lun_ref);
                                kref_put(&deve_tmp->pr_kref, target_pr_kref_release);
                                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()
                         */
                        dest_lun = rcu_dereference_check(deve_tmp->se_lun,
                                kref_read(&deve_tmp->pr_kref) != 0);

                        pr_reg_atp = __core_scsi3_do_alloc_registration(dev,
                                                nacl_tmp, dest_lun, deve_tmp,
                                                deve_tmp->mapped_lun, NULL,
                                                sa_res_key, all_tg_pt, aptpl);
                        if (!pr_reg_atp) {
                                percpu_ref_put(&lun_tmp->lun_ref);
                                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(&lun_tmp->lun_deve_lock);
                }
                spin_unlock(&lun_tmp->lun_deve_lock);

                spin_lock(&dev->se_port_lock);
                percpu_ref_put(&lun_tmp->lun_ref);
        }
        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,
        u64 mapped_lun,
        unsigned char *t_port,
        u16 tpgt,
        u64 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;
        }

        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_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] = { };

        core_pr_dump_initiator_port(pr_reg, i_buf, 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->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->fabric_name, node_acl->initiatorname,
                i_buf);
}

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

static int __core_scsi3_check_aptpl_registration(
        struct se_device *dev,
        struct se_portal_group *tpg,
        struct se_lun *lun,
        u64 target_lun,
        struct se_node_acl *nacl,
        u64 mapped_lun)
{
        struct t10_pr_registration *pr_reg, *pr_reg_tmp;
        struct t10_reservation *pr_tmpl = &dev->t10_pr;
        unsigned char i_port[PR_APTPL_MAX_IPORT_LEN] = { };
        unsigned char t_port[PR_APTPL_MAX_TPORT_LEN] = { };
        u16 tpgt;

        /*
         * 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 == mapped_lun) &&
                    !(strcmp(pr_reg->pr_tport, t_port)) &&
                     (pr_reg->pr_reg_tpgt == tpgt) &&
                     (pr_reg->pr_aptpl_target_lun == target_lun)) {
                        /*
                         * Obtain the ->pr_reg_deve pointer + reference, that
                         * is released by __core_scsi3_add_registration() below.
                         */
                        rcu_read_lock();
                        pr_reg->pr_reg_deve = target_nacl_find_deve(nacl, mapped_lun);
                        if (!pr_reg->pr_reg_deve) {
                                pr_err("Unable to locate PR APTPL %s mapped_lun:"
                                        " %llu\n", nacl->initiatorname, mapped_lun);
                                rcu_read_unlock();
                                continue;
                        }
                        kref_get(&pr_reg->pr_reg_deve->pr_kref);
                        rcu_read_unlock();

                        pr_reg->pr_reg_nacl = nacl;
                        pr_reg->tg_pt_sep_rtpi = lun->lun_rtpi;
                        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_node_acl *nacl,
        u64 mapped_lun)
{
        if (dev->dev_reservation_flags & DRF_SPC2_RESERVATIONS)
                return 0;

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

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

        core_pr_dump_initiator_port(pr_reg, i_buf, PR_REG_ISID_ID_LEN);

        pr_debug("SPC-3 PR [%s] Service Action: REGISTER%s Initiator"
                " Node: %s%s\n", tfo->fabric_name, (register_type == REGISTER_AND_MOVE) ?
                "_AND_MOVE" : (register_type == REGISTER_AND_IGNORE_EXISTING_KEY) ?
                "_AND_IGNORE_EXISTING_KEY" : "", nacl->initiatorname,
                i_buf);
        pr_debug("SPC-3 PR [%s] registration on Target Port: %s,0x%04x\n",
                 tfo->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->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->fabric_name,
                pr_reg->pr_res_key, pr_reg->pr_res_generation,
                pr_reg->pr_reg_aptpl);
}

static void __core_scsi3_add_registration(
        struct se_device *dev,
        struct se_node_acl *nacl,
        struct t10_pr_registration *pr_reg,
        enum register_type register_type,
        int register_move)
{
        const 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->t10_pr;
        struct se_dev_entry *deve;

        /*
         * 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) ?
                        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);

        __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)
                goto out;
        /*
         * 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) {
                struct se_node_acl *nacl_tmp = pr_reg_tmp->pr_reg_nacl;

                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);

                __core_scsi3_dump_registration(tfo, dev, nacl_tmp, pr_reg_tmp,
                                               register_type);
                spin_unlock(&pr_tmpl->registration_lock);
                /*
                 * Drop configfs group dependency reference and deve->pr_kref
                 * obtained from  __core_scsi3_alloc_registration() code.
                 */
                rcu_read_lock();
                deve = pr_reg_tmp->pr_reg_deve;
                if (deve) {
                        set_bit(DEF_PR_REG_ACTIVE, &deve->deve_flags);
                        core_scsi3_lunacl_undepend_item(deve);
                        pr_reg_tmp->pr_reg_deve = NULL;
                }
                rcu_read_unlock();
        }
out:
        /*
         * Drop deve->pr_kref obtained in __core_scsi3_do_alloc_registration()
         */
        rcu_read_lock();
        deve = pr_reg->pr_reg_deve;
        if (deve) {
                set_bit(DEF_PR_REG_ACTIVE, &deve->deve_flags);
                kref_put(&deve->pr_kref, target_pr_kref_release);
                pr_reg->pr_reg_deve = NULL;
        }
        rcu_read_unlock();
}

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

        pr_reg = __core_scsi3_alloc_registration(dev, nacl, lun, deve, mapped_lun,
                                                 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->t10_pr;
        struct t10_pr_registration *pr_reg, *pr_reg_tmp;

        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;

                /*
                 * If this registration does NOT contain a fabric provided
                 * ISID, then we have found a match.
                 */
                if (!pr_reg->isid_present_at_reg) {
                        atomic_inc_mb(&pr_reg->pr_res_holders);
                        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_mb(&pr_reg->pr_res_holders);
                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] = { };
        unsigned char *isid_ptr = NULL;

        if (tpg->se_tpg_tfo->sess_get_initiator_sid != NULL) {
                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_mb(&pr_reg->pr_res_holders);
}

static int core_scsi3_check_implicit_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 implicit 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, 1);
                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 implicitly 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;
}

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)
        __releases(&pr_tmpl->registration_lock)
        __acquires(&pr_tmpl->registration_lock)
{
        const struct target_core_fabric_ops *tfo =
                        pr_reg->pr_reg_nacl->se_tpg->se_tpg_tfo;
        struct t10_reservation *pr_tmpl = &dev->t10_pr;
        struct se_node_acl *nacl = pr_reg->pr_reg_nacl;
        struct se_dev_entry *deve;
        char i_buf[PR_REG_ISID_ID_LEN] = { };

        lockdep_assert_held(&pr_tmpl->registration_lock);

        core_pr_dump_initiator_port(pr_reg, i_buf, PR_REG_ISID_ID_LEN);

        if (!list_empty(&pr_reg->pr_reg_list))
                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);

        spin_unlock(&pr_tmpl->registration_lock);
        /*
         * 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) {
                pr_debug("SPC-3 PR [%s] waiting for pr_res_holders\n",
                                tfo->fabric_name);
                cpu_relax();
        }

        rcu_read_lock();
        deve = target_nacl_find_deve(nacl, pr_reg->pr_res_mapped_lun);
        if (deve)
                clear_bit(DEF_PR_REG_ACTIVE, &deve->deve_flags);
        rcu_read_unlock();

        spin_lock(&pr_tmpl->registration_lock);
        pr_debug("SPC-3 PR [%s] Service Action: UNREGISTER Initiator"
                " Node: %s%s\n", tfo->fabric_name,
                pr_reg->pr_reg_nacl->initiatorname,
                i_buf);
        pr_debug("SPC-3 PR [%s] for %s TCM Subsystem %s Object Target"
                " Port(s)\n", tfo->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->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;
                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->t10_pr;
        struct t10_pr_registration *pr_reg, *pr_reg_tmp, *pr_res_holder;
        bool free_reg = false;
        /*
         * 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, 1);
                free_reg = true;
        }
        spin_unlock(&dev->dev_reservation_lock);
        /*
         * Release any registration associated with the struct se_node_acl.
         */
        spin_lock(&pr_tmpl->registration_lock);
        if (pr_res_holder && free_reg)
                __core_scsi3_free_registration(dev, pr_res_holder, NULL, 0);

        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->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, 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);
                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 target_depend_item(&tpg->tpg_group.cg_item);
}

static void core_scsi3_tpg_undepend_item(struct se_portal_group *tpg)
{
        target_undepend_item(&tpg->tpg_group.cg_item);
        atomic_dec_mb(&tpg->tpg_pr_ref_count);
}

static int core_scsi3_nodeacl_depend_item(struct se_node_acl *nacl)
{
        if (nacl->dynamic_node_acl)
                return 0;
        return target_depend_item(&nacl->acl_group.cg_item);
}

static void core_scsi3_nodeacl_undepend_item(struct se_node_acl *nacl)
{
        if (!nacl->dynamic_node_acl)
                target_undepend_item(&nacl->acl_group.cg_item);
        atomic_dec_mb(&nacl->acl_pr_ref_count);
}

static int core_scsi3_lunacl_depend_item(struct se_dev_entry *se_deve)
{
        struct se_lun_acl *lun_acl;

        /*
         * For nacl->dynamic_node_acl=1
         */
        lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
                                kref_read(&se_deve->pr_kref) != 0);
        if (!lun_acl)
                return 0;

        return target_depend_item(&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;

        /*
         * For nacl->dynamic_node_acl=1
         */
        lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
                                kref_read(&se_deve->pr_kref) != 0);
        if (!lun_acl) {
                kref_put(&se_deve->pr_kref, target_pr_kref_release);
                return;
        }

        target_undepend_item(&lun_acl->se_lun_group.cg_item);
        kref_put(&se_deve->pr_kref, target_pr_kref_release);
}

static sense_reason_t
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_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;
        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;
        unsigned char *buf, *ptr, proto_ident;
        const unsigned char *i_str = NULL;
        char *iport_ptr = NULL, i_buf[PR_REG_ISID_ID_LEN];
        sense_reason_t ret;
        u32 tpdl, tid_len = 0;
        u32 dest_rtpi = 0;

        /*
         * Allocate a struct pr_transport_id_holder and setup the
         * local_node_acl pointer 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");
                return TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
        }
        INIT_LIST_HEAD(&tidh_new->dest_list);
        tidh_new->dest_tpg = tpg;
        tidh_new->dest_node_acl = se_sess->se_node_acl;

        local_pr_reg = __core_scsi3_alloc_registration(cmd->se_dev,
                                se_sess->se_node_acl, cmd->se_lun,
                                NULL, cmd->orig_fe_lun, l_isid,
                                sa_res_key, all_tg_pt, aptpl);
        if (!local_pr_reg) {
                kfree(tidh_new);
                return TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
        }

        if (core_scsi3_lunacl_depend_item(local_pr_reg->pr_reg_deve)) {
                kfree(tidh_new);
                kref_put(&local_pr_reg->pr_reg_deve->pr_kref,
                         target_pr_kref_release);
                kmem_cache_free(t10_pr_reg_cache, local_pr_reg);
                return TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
        }

        tidh_new->dest_pr_reg = local_pr_reg;
        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);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out;
        }

        buf = transport_kmap_data_sg(cmd);
        if (!buf) {
                ret = TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
                goto out;
        }

        /*
         * 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 = get_unaligned_be32(&buf[24]);

        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);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out_unmap;
        }
        /*
         * 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) {
                struct se_lun *dest_lun, *tmp_lun;

                proto_ident = (ptr[0] & 0x0f);
                dest_tpg = NULL;

                spin_lock(&dev->se_port_lock);
                list_for_each_entry(tmp_lun, &dev->dev_sep_list, lun_dev_link) {
                        tmp_tpg = tmp_lun->lun_tpg;

                        /*
                         * Look for the matching proto_ident provided by
                         * the received TransportID
                         */
                        if (tmp_tpg->proto_id != proto_ident)
                                continue;
                        dest_rtpi = tmp_lun->lun_rtpi;

                        iport_ptr = NULL;
                        i_str = target_parse_pr_out_transport_id(tmp_tpg,
                                        ptr, &tid_len, &iport_ptr);
                        if (!i_str)
                                continue;
                        /*
                         * 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 &&
                            dev->dev_attrib.enforce_pr_isids &&
                            !iport_ptr) {
                                pr_warn("SPC-PR: enforce_pr_isids is set but a isid has not been sent in the SPEC_I_PT data for %s.",
                                        i_str);
                                ret = TCM_INVALID_PARAMETER_LIST;
                                spin_unlock(&dev->se_port_lock);
                                goto out_unmap;
                        }

                        atomic_inc_mb(&tmp_tpg->tpg_pr_ref_count);
                        spin_unlock(&dev->se_port_lock);

                        if (core_scsi3_tpg_depend_item(tmp_tpg)) {
                                pr_err(" core_scsi3_tpg_depend_item()"
                                        " for tmp_tpg\n");
                                atomic_dec_mb(&tmp_tpg->tpg_pr_ref_count);
                                ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                                goto out_unmap;
                        }
                        /*
                         * Locate the destination initiator ACL to be registered
                         * from the decoded fabric module specific TransportID
                         * at *i_str.
                         */
                        mutex_lock(&tmp_tpg->acl_node_mutex);
                        dest_node_acl = __core_tpg_get_initiator_node_acl(
                                                tmp_tpg, i_str);
                        if (dest_node_acl)
                                atomic_inc_mb(&dest_node_acl->acl_pr_ref_count);
                        mutex_unlock(&tmp_tpg->acl_node_mutex);

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

                        if (core_scsi3_nodeacl_depend_item(dest_node_acl)) {
                                pr_err("configfs_depend_item() failed"
                                        " for dest_node_acl->acl_group\n");
                                atomic_dec_mb(&dest_node_acl->acl_pr_ref_count);
                                core_scsi3_tpg_undepend_item(tmp_tpg);
                                ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                                goto out_unmap;
                        }

                        dest_tpg = tmp_tpg;
                        pr_debug("SPC-3 PR SPEC_I_PT: Located %s Node: %s Port RTPI: %u\n",
                                dest_tpg->se_tpg_tfo->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");
                        ret = TCM_INVALID_PARAMETER_LIST;
                        goto out_unmap;
                }

                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->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);
                        ret = TCM_INVALID_PARAMETER_LIST;
                        goto out_unmap;
                }
                /*
                 * 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: %u\n",
                                dest_tpg->se_tpg_tfo->fabric_name,
                                dest_rtpi);

                        core_scsi3_nodeacl_undepend_item(dest_node_acl);
                        core_scsi3_tpg_undepend_item(dest_tpg);
                        ret = TCM_INVALID_PARAMETER_LIST;
                        goto out_unmap;
                }

                if (core_scsi3_lunacl_depend_item(dest_se_deve)) {
                        pr_err("core_scsi3_lunacl_depend_item()"
                                        " failed\n");
                        kref_put(&dest_se_deve->pr_kref, target_pr_kref_release);
                        core_scsi3_nodeacl_undepend_item(dest_node_acl);
                        core_scsi3_tpg_undepend_item(dest_tpg);
                        ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                        goto out_unmap;
                }

                pr_debug("SPC-3 PR SPEC_I_PT: Located %s Node: %s"
                        " dest_se_deve mapped_lun: %llu\n",
                        dest_tpg->se_tpg_tfo->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);
                        ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                        goto out_unmap;
                }
                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_lun = rcu_dereference_check(dest_se_deve->se_lun,
                                kref_read(&dest_se_deve->pr_kref) != 0);

                dest_pr_reg = __core_scsi3_alloc_registration(cmd->se_dev,
                                        dest_node_acl, dest_lun, dest_se_deve,
                                        dest_se_deve->mapped_lun, 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);
                        ret = TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
                        goto out_unmap;
                }
                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;

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

                memset(i_buf, 0, PR_REG_ISID_ID_LEN);
                core_pr_dump_initiator_port(dest_pr_reg, i_buf, 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:"
                        " %llu\n", dest_tpg->se_tpg_tfo->fabric_name,
                        dest_node_acl->initiatorname, i_buf, (dest_se_deve) ?
                        dest_se_deve->mapped_lun : 0);

                if (dest_pr_reg == local_pr_reg)
                        continue;

                core_scsi3_nodeacl_undepend_item(dest_node_acl);
                core_scsi3_tpg_undepend_item(dest_tpg);
        }

        return 0;
out_unmap:
        transport_kunmap_data_sg(cmd);
out:
        /*
         * 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) {
                bool is_local = false;

                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;

                if (dest_pr_reg == local_pr_reg)
                        is_local = true;

                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);
                }

                kmem_cache_free(t10_pr_reg_cache, dest_pr_reg);
                core_scsi3_lunacl_undepend_item(dest_se_deve);

                if (is_local)
                        continue;

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

static int core_scsi3_update_aptpl_buf(
        struct se_device *dev,
        unsigned char *buf,
        u32 pr_aptpl_buf_len)
{
        struct se_portal_group *tpg;
        struct t10_pr_registration *pr_reg;
        unsigned char tmp[512], isid_buf[32];
        ssize_t len = 0;
        int reg_count = 0;
        int ret = 0;

        spin_lock(&dev->dev_reservation_lock);
        spin_lock(&dev->t10_pr.registration_lock);
        /*
         * Walk the registration list..
         */
        list_for_each_entry(pr_reg, &dev->t10_pr.registration_list,
                        pr_reg_list) {

                tmp[0] = '\0';
                isid_buf[0] = '\0';
                tpg = pr_reg->pr_reg_nacl->se_tpg;
                /*
                 * 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=%llu\n", reg_count,
                                tpg->se_tpg_tfo->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=%llu\n",
                                reg_count, tpg->se_tpg_tfo->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,"
                               " reallocating larger buffer\n");
                        ret = -EMSGSIZE;
                        goto out;
                }
                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=%llu\nPR_REG_END:"
                        " %d\n", tpg->se_tpg_tfo->fabric_name,
                        tpg->se_tpg_tfo->tpg_get_wwn(tpg),
                        tpg->se_tpg_tfo->tpg_get_tag(tpg),
                        pr_reg->tg_pt_sep_rtpi, pr_reg->pr_aptpl_target_lun,
                        reg_count);

                if ((len + strlen(tmp) >= pr_aptpl_buf_len)) {
                        pr_err("Unable to update renaming APTPL metadata,"
                               " reallocating larger buffer\n");
                        ret = -EMSGSIZE;
                        goto out;
                }
                len += sprintf(buf+len, "%s", tmp);
                reg_count++;
        }

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

out:
        spin_unlock(&dev->t10_pr.registration_lock);
        spin_unlock(&dev->dev_reservation_lock);

        return ret;
}

static int __core_scsi3_write_aptpl_to_file(
        struct se_device *dev,
        unsigned char *buf)
{
        struct t10_wwn *wwn = &dev->t10_wwn;
        struct file *file;
        int flags = O_RDWR | O_CREAT | O_TRUNC;
        char *path;
        u32 pr_aptpl_buf_len;
        int ret;
        loff_t pos = 0;

        path = kasprintf(GFP_KERNEL, "%s/pr/aptpl_%s", db_root,
                        &wwn->unit_serial[0]);
        if (!path)
                return -ENOMEM;

        file = filp_open(path, flags, 0600);
        if (IS_ERR(file)) {
                pr_err("filp_open(%s) for APTPL metadata"
                        " failed\n", path);
                kfree(path);
                return PTR_ERR(file);
        }

        pr_aptpl_buf_len = (strlen(buf) + 1); /* Add extra for NULL */

        ret = kernel_write(file, buf, pr_aptpl_buf_len, &pos);

        if (ret < 0)
                pr_debug("Error writing APTPL metadata file: %s\n", path);
        fput(file);
        kfree(path);

        return (ret < 0) ? -EIO : 0;
}

/*

 * Clear the APTPL metadata if APTPL has been disabled, otherwise
 * write out the updated metadata to struct file for this SCSI device.
 */
static sense_reason_t core_scsi3_update_and_write_aptpl(struct se_device *dev, bool aptpl)
{
        unsigned char *buf;
        int rc, len = PR_APTPL_BUF_LEN;

        if (!aptpl) {
                char *null_buf = "No Registrations or Reservations\n";

                rc = __core_scsi3_write_aptpl_to_file(dev, null_buf);
                dev->t10_pr.pr_aptpl_active = 0;
                pr_debug("SPC-3 PR: Set APTPL Bit Deactivated\n");

                if (rc)
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

                return 0;
        }
retry:
        buf = vzalloc(len);
        if (!buf)
                return TCM_OUT_OF_RESOURCES;

        rc = core_scsi3_update_aptpl_buf(dev, buf, len);
        if (rc < 0) {
                vfree(buf);
                len *= 2;
                goto retry;
        }

        rc = __core_scsi3_write_aptpl_to_file(dev, buf);
        if (rc != 0) {
                pr_err("SPC-3 PR: Could not update APTPL\n");
                vfree(buf);
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        dev->t10_pr.pr_aptpl_active = 1;
        vfree(buf);
        pr_debug("SPC-3 PR: Set APTPL Bit Activated\n");
        return 0;
}

static sense_reason_t
core_scsi3_emulate_pro_register(struct se_cmd *cmd, u64 res_key, u64 sa_res_key,
                bool aptpl, bool all_tg_pt, bool spec_i_pt, enum register_type register_type)
{
        struct se_session *se_sess = cmd->se_sess;
        struct se_device *dev = cmd->se_dev;
        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;
        struct t10_reservation *pr_tmpl = &dev->t10_pr;
        unsigned char isid_buf[PR_REG_ISID_LEN] = { };
        unsigned char *isid_ptr = NULL;
        sense_reason_t ret = TCM_NO_SENSE;
        int pr_holder = 0, type;

        if (!se_sess || !se_lun) {
                pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        se_tpg = se_sess->se_tpg;

        if (se_tpg->se_tpg_tfo->sess_get_initiator_sid) {
                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 = core_scsi3_locate_pr_reg(dev, se_sess->se_node_acl, se_sess);
        if (!pr_reg) {
                if (res_key) {
                        pr_warn("SPC-3 PR: Reservation Key non-zero"
                                " for SA REGISTER, returning CONFLICT\n");
                        return TCM_RESERVATION_CONFLICT;
                }
                /*
                 * 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.
                         */
                        if (core_scsi3_alloc_registration(cmd->se_dev,
                                        se_sess->se_node_acl, cmd->se_lun,
                                        NULL, cmd->orig_fe_lun, isid_ptr,
                                        sa_res_key, all_tg_pt, aptpl,
                                        register_type, 0)) {
                                pr_err("Unable to allocate"
                                        " struct t10_pr_registration\n");
                                return TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
                        }
                } 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;
                }
                return core_scsi3_update_and_write_aptpl(dev, aptpl);
        }

        /* ok, existing registration */

        if ((register_type == REGISTER) && (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);
                ret = TCM_RESERVATION_CONFLICT;
                goto out;
        }

        if (spec_i_pt) {
                pr_err("SPC-3 PR REGISTER: SPEC_I_PT"
                        " set on a registered nexus\n");
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out;
        }

        /*
         * 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 REGISTER: ALL_TG_PT=1"
                        " registration exists, but ALL_TG_PT=1 bit not"
                        " present in received PROUT\n");
                ret = TCM_INVALID_CDB_FIELD;
                goto out;
        }

        /*
         * sa_res_key=1 Change Reservation Key for registered I_T Nexus.
         */
        if (sa_res_key) {
                /*
                 * 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->fabric_name,
                         (register_type == REGISTER_AND_IGNORE_EXISTING_KEY) ? "_AND_IGNORE_EXISTING_KEY" : "",
                         pr_reg->pr_reg_nacl->initiatorname,
                         pr_reg->pr_res_key, pr_reg->pr_res_generation);

        } else {
                /*
                 * sa_res_key=0 Unregister Reservation Key for registered I_T Nexus.
                 */
                type = pr_reg->pr_res_type;
                pr_holder = core_scsi3_check_implicit_release(cmd->se_dev,
                                                              pr_reg);
                if (pr_holder < 0) {
                        ret = TCM_RESERVATION_CONFLICT;
                        goto out;
                }

                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);
                pr_reg = NULL;

                /*
                 * 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) {

                                target_ua_allocate_lun(
                                        pr_reg_p->pr_reg_nacl,
                                        pr_reg_p->pr_res_mapped_lun,
                                        0x2A,
                                        ASCQ_2AH_RESERVATIONS_RELEASED);
                        }
                }

                spin_unlock(&pr_tmpl->registration_lock);
        }

        ret = core_scsi3_update_and_write_aptpl(dev, aptpl);

out:
        if (pr_reg)
                core_scsi3_put_pr_reg(pr_reg);
        return ret;
}

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 sense_reason_t
core_scsi3_pro_reserve(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_res_holder;
        struct t10_reservation *pr_tmpl = &dev->t10_pr;
        char i_buf[PR_REG_ISID_ID_LEN] = { };
        sense_reason_t ret;

        if (!se_sess || !se_lun) {
                pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        /*
         * 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");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        /*
         * 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);
                ret = TCM_RESERVATION_CONFLICT;
                goto out_put_pr_reg;
        }
        /*
         * 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);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out_put_pr_reg;
        }
        /*
         * 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 (!is_reservation_holder(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->fabric_name,
                                se_sess->se_node_acl->initiatorname,
                                pr_res_nacl->se_tpg->se_tpg_tfo->fabric_name,
                                pr_res_holder->pr_reg_nacl->initiatorname);

                        spin_unlock(&dev->dev_reservation_lock);
                        ret = TCM_RESERVATION_CONFLICT;
                        goto out_put_pr_reg;
                }
                /*
                 * 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->fabric_name,
                                se_sess->se_node_acl->initiatorname,
                                pr_res_nacl->se_tpg->se_tpg_tfo->fabric_name,
                                pr_res_holder->pr_reg_nacl->initiatorname);

                        spin_unlock(&dev->dev_reservation_lock);
                        ret = TCM_RESERVATION_CONFLICT;
                        goto out_put_pr_reg;
                }
                /*
                 * 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);
                ret = 0;
                goto out_put_pr_reg;
        }
        /*
         * 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;
        core_pr_dump_initiator_port(pr_reg, i_buf, 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->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->fabric_name,
                        se_sess->se_node_acl->initiatorname,
                        i_buf);
        spin_unlock(&dev->dev_reservation_lock);

        if (pr_tmpl->pr_aptpl_active)
                core_scsi3_update_and_write_aptpl(cmd->se_dev, true);

        ret = 0;
out_put_pr_reg:
        core_scsi3_put_pr_reg(pr_reg);
        return ret;
}

static sense_reason_t
core_scsi3_emulate_pro_reserve(struct se_cmd *cmd, int type, int scope,
                u64 res_key)
{
        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:
                return core_scsi3_pro_reserve(cmd, type, scope, res_key);
        default:
                pr_err("SPC-3 PR: Unknown Service Action RESERVE Type:"
                        " 0x%02x\n", type);
                return TCM_INVALID_CDB_FIELD;
        }
}

static void __core_scsi3_complete_pro_release(
        struct se_device *dev,
        struct se_node_acl *se_nacl,
        struct t10_pr_registration *pr_reg,
        int explicit,
        int unreg)
{
        const struct target_core_fabric_ops *tfo = se_nacl->se_tpg->se_tpg_tfo;
        char i_buf[PR_REG_ISID_ID_LEN] = { };
        int pr_res_type = 0, pr_res_scope = 0;

        lockdep_assert_held(&dev->dev_reservation_lock);

        core_pr_dump_initiator_port(pr_reg, i_buf, PR_REG_ISID_ID_LEN);
        /*
         * Go ahead and release the current PR reservation holder.
         * If an All Registrants reservation is currently active and
         * a unregister operation is requested, replace the current
         * dev_pr_res_holder with another active registration.
         */
        if (dev->dev_pr_res_holder) {
                pr_res_type = dev->dev_pr_res_holder->pr_res_type;
                pr_res_scope = dev->dev_pr_res_holder->pr_res_scope;
                dev->dev_pr_res_holder->pr_res_type = 0;
                dev->dev_pr_res_holder->pr_res_scope = 0;
                dev->dev_pr_res_holder->pr_res_holder = 0;
                dev->dev_pr_res_holder = NULL;
        }
        if (!unreg)
                goto out;

        spin_lock(&dev->t10_pr.registration_lock);
        list_del_init(&pr_reg->pr_reg_list);
        /*
         * If the I_T nexus is a reservation holder, the persistent reservation
         * is of an all registrants type, and the I_T nexus is the last remaining
         * registered I_T nexus, then the device server shall also release the
         * persistent reservation.
         */
        if (!list_empty(&dev->t10_pr.registration_list) &&
            ((pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG) ||
             (pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG))) {
                dev->dev_pr_res_holder =
                        list_entry(dev->t10_pr.registration_list.next,
                                   struct t10_pr_registration, pr_reg_list);
                dev->dev_pr_res_holder->pr_res_type = pr_res_type;
                dev->dev_pr_res_holder->pr_res_scope = pr_res_scope;
                dev->dev_pr_res_holder->pr_res_holder = 1;
        }
        spin_unlock(&dev->t10_pr.registration_lock);
out:
        if (!dev->dev_pr_res_holder) {
                pr_debug("SPC-3 PR [%s] Service Action: %s RELEASE cleared"
                        " reservation holder TYPE: %s ALL_TG_PT: %d\n",
                        tfo->fabric_name, (explicit) ? "explicit" :
                        "implicit", core_scsi3_pr_dump_type(pr_res_type),
                        (pr_reg->pr_reg_all_tg_pt) ? 1 : 0);
        }
        pr_debug("SPC-3 PR [%s] RELEASE Node: %s%s\n",
                tfo->fabric_name, se_nacl->initiatorname,
                i_buf);
        /*
         * 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 sense_reason_t
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->t10_pr;
        sense_reason_t ret = 0;

        if (!se_sess || !se_lun) {
                pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        /*
         * 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");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        /*
         * 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);
                goto out_put_pr_reg;
        }

        if (!is_reservation_holder(pr_res_holder, pr_reg)) {
                /*
                 * Release request from a registered I_T nexus that is not a
                 * persistent reservation holder. return GOOD status.
                 */
                spin_unlock(&dev->dev_reservation_lock);
                goto out_put_pr_reg;
        }

        /*
         * 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);
                ret = TCM_RESERVATION_CONFLICT;
                goto out_put_pr_reg;
        }
        /*
         * 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->fabric_name,
                        se_sess->se_node_acl->initiatorname,
                        pr_res_nacl->se_tpg->se_tpg_tfo->fabric_name,
                        pr_res_holder->pr_reg_nacl->initiatorname);

                spin_unlock(&dev->dev_reservation_lock);
                ret = TCM_RESERVATION_CONFLICT;
                goto out_put_pr_reg;
        }
        /*
         * 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, 0);

        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;

                target_ua_allocate_lun(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)
                core_scsi3_update_and_write_aptpl(cmd->se_dev, true);

out_put_pr_reg:
        core_scsi3_put_pr_reg(pr_reg);
        return ret;
}

static sense_reason_t
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->t10_pr;
        struct t10_pr_registration *pr_reg, *pr_reg_tmp, *pr_reg_n, *pr_res_holder;
        u64 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");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        /*
         * 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);
                return TCM_RESERVATION_CONFLICT;
        }
        /*
         * 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, 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)
                        target_ua_allocate_lun(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->fabric_name);

        core_scsi3_update_and_write_aptpl(cmd->se_dev, false);

        core_scsi3_pr_generation(dev);
        return 0;
}

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,
        enum preempt_type preempt_type)
{
        struct se_node_acl *nacl = pr_reg->pr_reg_nacl;
        const struct target_core_fabric_ops *tfo = nacl->se_tpg->se_tpg_tfo;
        char i_buf[PR_REG_ISID_ID_LEN] = { };

        lockdep_assert_held(&dev->dev_reservation_lock);

        core_pr_dump_initiator_port(pr_reg, i_buf, PR_REG_ISID_ID_LEN);
        /*
         * Do an implicit RELEASE of the existing reservation.
         */
        if (dev->dev_pr_res_holder)
                __core_scsi3_complete_pro_release(dev, nacl,
                                                  dev->dev_pr_res_holder, 0, 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->fabric_name, (preempt_type == PREEMPT_AND_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->fabric_name, (preempt_type == PREEMPT_AND_ABORT) ? "_AND_ABORT" : "",
                nacl->initiatorname, i_buf);
        /*
         * 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;
                kmem_cache_free(t10_pr_reg_cache, pr_reg);
        }
}

static sense_reason_t
core_scsi3_pro_preempt(struct se_cmd *cmd, int type, int scope, u64 res_key,
                u64 sa_res_key, enum preempt_type preempt_type)
{
        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->t10_pr;
        u64 pr_res_mapped_lun = 0;
        int all_reg = 0, calling_it_nexus = 0;
        bool sa_res_key_unmatched = sa_res_key != 0;
        int prh_type = 0, prh_scope = 0;

        if (!se_sess)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        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",
                        (preempt_type == PREEMPT_AND_ABORT) ? "_AND_ABORT" : "");
                return TCM_RESERVATION_CONFLICT;
        }
        if (pr_reg_n->pr_res_key != res_key) {
                core_scsi3_put_pr_reg(pr_reg_n);
                return TCM_RESERVATION_CONFLICT;
        }
        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);
                return TCM_INVALID_PARAMETER_LIST;
        }

        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);
                return TCM_INVALID_PARAMETER_LIST;
        }
        /*
         * 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;
                                sa_res_key_unmatched = false;

                                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,
                                        (preempt_type == PREEMPT_AND_ABORT) ? &preempt_and_abort_list :
                                                NULL, calling_it_nexus);
                        } 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 implicit
                                 * 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;
                                sa_res_key_unmatched = false;

                                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,
                                        (preempt_type == PREEMPT_AND_ABORT) ? &preempt_and_abort_list :
                                                NULL, 0);
                        }
                        if (!calling_it_nexus)
                                target_ua_allocate_lun(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 (sa_res_key_unmatched) {
                        spin_unlock(&dev->dev_reservation_lock);
                        core_scsi3_put_pr_reg(pr_reg_n);
                        return TCM_RESERVATION_CONFLICT;
                }
                /*
                 * 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,
                                (preempt_type == PREEMPT_AND_ABORT) ? &preempt_and_abort_list : NULL,
                                type, scope, preempt_type);

                        if (preempt_type == PREEMPT_AND_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)
                        core_scsi3_update_and_write_aptpl(cmd->se_dev, true);

                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, 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,
                                (preempt_type == PREEMPT_AND_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;
                 */
                target_ua_allocate_lun(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,
                        (preempt_type == PREEMPT_AND_ABORT) ? &preempt_and_abort_list : NULL,
                        type, scope, preempt_type);
        /*
         * 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;

                        target_ua_allocate_lun(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 (preempt_type == PREEMPT_AND_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)
                core_scsi3_update_and_write_aptpl(cmd->se_dev, true);

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

static sense_reason_t
core_scsi3_emulate_pro_preempt(struct se_cmd *cmd, int type, int scope,
                u64 res_key, u64 sa_res_key, enum preempt_type preempt_type)
{
        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:
                return core_scsi3_pro_preempt(cmd, type, scope, res_key,
                                              sa_res_key, preempt_type);
        default:
                pr_err("SPC-3 PR: Unknown Service Action PREEMPT%s"
                        " Type: 0x%02x\n", (preempt_type == PREEMPT_AND_ABORT) ? "_AND_ABORT" : "", type);
                return TCM_INVALID_CDB_FIELD;
        }
}


static sense_reason_t
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, *tmp_lun;
        struct se_node_acl *pr_res_nacl, *pr_reg_nacl, *dest_node_acl = NULL;
        struct se_portal_group *se_tpg, *dest_se_tpg = NULL;
        const 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->t10_pr;
        unsigned char *buf;
        const unsigned char *initiator_str;
        char *iport_ptr = NULL, i_buf[PR_REG_ISID_ID_LEN] = { };
        u32 tid_len, tmp_tid_len;
        int new_reg = 0, type, scope, matching_iname;
        sense_reason_t ret;
        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");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        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");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        /*
         * 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);
                ret = TCM_RESERVATION_CONFLICT;
                goto out_put_pr_reg;
        }
        /*
         * 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");
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out_put_pr_reg;
        }

        /*
         * 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);
        if (!buf) {
                ret = TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
                goto out_put_pr_reg;
        }

        rtpi = get_unaligned_be16(&buf[18]);
        tid_len = get_unaligned_be32(&buf[20]);
        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);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out_put_pr_reg;
        }

        spin_lock(&dev->se_port_lock);
        list_for_each_entry(tmp_lun, &dev->dev_sep_list, lun_dev_link) {
                if (tmp_lun->lun_rtpi != rtpi)
                        continue;
                dest_se_tpg = tmp_lun->lun_tpg;
                dest_tf_ops = dest_se_tpg->se_tpg_tfo;
                if (!dest_tf_ops)
                        continue;

                atomic_inc_mb(&dest_se_tpg->tpg_pr_ref_count);
                spin_unlock(&dev->se_port_lock);

                if (core_scsi3_tpg_depend_item(dest_se_tpg)) {
                        pr_err("core_scsi3_tpg_depend_item() failed"
                                " for dest_se_tpg\n");
                        atomic_dec_mb(&dest_se_tpg->tpg_pr_ref_count);
                        ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                        goto out_put_pr_reg;
                }

                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);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out_put_pr_reg;
        }

        buf = transport_kmap_data_sg(cmd);
        if (!buf) {
                ret = TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
                goto out_put_pr_reg;
        }
        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_se_tpg->proto_id) {
                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_se_tpg->proto_id,
                        dest_tf_ops->fabric_name);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out;
        }
        initiator_str = target_parse_pr_out_transport_id(dest_se_tpg,
                        &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");
                ret = TCM_INVALID_PARAMETER_LIST;
                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->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);
                ret = TCM_INVALID_PARAMETER_LIST;
                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);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out;
        }
after_iport_check:
        /*
         * Locate the destination struct se_node_acl from the received Transport ID
         */
        mutex_lock(&dest_se_tpg->acl_node_mutex);
        dest_node_acl = __core_tpg_get_initiator_node_acl(dest_se_tpg,
                                initiator_str);
        if (dest_node_acl)
                atomic_inc_mb(&dest_node_acl->acl_pr_ref_count);
        mutex_unlock(&dest_se_tpg->acl_node_mutex);

        if (!dest_node_acl) {
                pr_err("Unable to locate %s dest_node_acl for"
                        " TransportID%s\n", dest_tf_ops->fabric_name,
                        initiator_str);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out;
        }

        if (core_scsi3_nodeacl_depend_item(dest_node_acl)) {
                pr_err("core_scsi3_nodeacl_depend_item() for"
                        " dest_node_acl\n");
                atomic_dec_mb(&dest_node_acl->acl_pr_ref_count);
                dest_node_acl = NULL;
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out;
        }

        pr_debug("SPC-3 PR REGISTER_AND_MOVE: Found %s dest_node_acl:"
                " %s from TransportID\n", dest_tf_ops->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->fabric_name, rtpi);
                ret = TCM_INVALID_PARAMETER_LIST;
                goto out;
        }

        if (core_scsi3_lunacl_depend_item(dest_se_deve)) {
                pr_err("core_scsi3_lunacl_depend_item() failed\n");
                kref_put(&dest_se_deve->pr_kref, target_pr_kref_release);
                dest_se_deve = NULL;
                ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                goto out;
        }

        pr_debug("SPC-3 PR REGISTER_AND_MOVE: Located %s node %s LUN"
                " ACL for dest_se_deve->mapped_lun: %llu\n",
                dest_tf_ops->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);
                ret = TCM_INVALID_CDB_FIELD;
                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 (!is_reservation_holder(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);
                ret = TCM_RESERVATION_CONFLICT;
                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);
                ret = TCM_RESERVATION_CONFLICT;
                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) {
                struct se_lun *dest_lun = rcu_dereference_check(dest_se_deve->se_lun,
                                kref_read(&dest_se_deve->pr_kref) != 0);

                spin_unlock(&dev->dev_reservation_lock);
                if (core_scsi3_alloc_registration(cmd->se_dev, dest_node_acl,
                                        dest_lun, dest_se_deve, dest_se_deve->mapped_lun,
                                        iport_ptr, sa_res_key, 0, aptpl, 2, 1)) {
                        ret = TCM_INSUFFICIENT_REGISTRATION_RESOURCES;
                        goto out;
                }
                spin_lock(&dev->dev_reservation_lock);
                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, 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;
        core_pr_dump_initiator_port(pr_reg, i_buf, 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->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->fabric_name, pr_reg_nacl->initiatorname,
                i_buf, dest_tf_ops->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);

        core_scsi3_update_and_write_aptpl(cmd->se_dev, aptpl);

        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);

out_put_pr_reg:
        core_scsi3_put_pr_reg(pr_reg);
        return ret;
}

/*
 * See spc4r17 section 6.14 Table 170
 */
sense_reason_t
target_scsi3_emulate_pr_out(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        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;
        sense_reason_t 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_reservation_flags & DRF_SPC2_RESERVATIONS) {
                pr_err("Received PERSISTENT_RESERVE CDB while legacy"
                        " SPC-2 reservation is held, returning"
                        " RESERVATION_CONFLICT\n");
                return TCM_RESERVATION_CONFLICT;
        }

        /*
         * 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)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        if (cmd->data_length < 24) {
                pr_warn("SPC-PR: Received PR OUT parameter list"
                        " length too small: %u\n", cmd->data_length);
                return TCM_PARAMETER_LIST_LENGTH_ERROR;
        }

        /*
         * 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);
        if (!buf)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        /*
         * From PERSISTENT_RESERVE_OUT parameter list (payload)
         */
        res_key = get_unaligned_be64(&buf[0]);
        sa_res_key = get_unaligned_be64(&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);
        }
        /*
         * If the backend device has been configured to force APTPL metadata
         * write-out, go ahead and propigate aptpl=1 down now.
         */
        if (dev->dev_attrib.force_pr_aptpl)
                aptpl = 1;

        transport_kunmap_data_sg(cmd);
        buf = NULL;

        /*
         * SPEC_I_PT=1 is only valid for Service action: REGISTER
         */
        if (spec_i_pt && (sa != PRO_REGISTER))
                return TCM_INVALID_PARAMETER_LIST;

        /*
         * 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 && (sa != PRO_REGISTER_AND_MOVE) &&
            (cmd->data_length != 24)) {
                pr_warn("SPC-PR: Received PR OUT illegal parameter"
                        " list length: %u\n", cmd->data_length);
                return TCM_PARAMETER_LIST_LENGTH_ERROR;
        }

        /*
         * (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, REGISTER);
                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, PREEMPT);
                break;
        case PRO_PREEMPT_AND_ABORT:
                ret = core_scsi3_emulate_pro_preempt(cmd, type, scope,
                                        res_key, sa_res_key, PREEMPT_AND_ABORT);
                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, REGISTER_AND_IGNORE_EXISTING_KEY);
                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", sa);
                return TCM_INVALID_CDB_FIELD;
        }

        if (!ret)
                target_complete_cmd(cmd, SAM_STAT_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 sense_reason_t
core_scsi3_pri_read_keys(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_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);
                return TCM_INVALID_CDB_FIELD;
        }

        buf = transport_kmap_data_sg(cmd);
        if (!buf)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        put_unaligned_be32(dev->t10_pr.pr_generation, buf);

        spin_lock(&dev->t10_pr.registration_lock);
        list_for_each_entry(pr_reg, &dev->t10_pr.registration_list,
                        pr_reg_list) {
                /*
                 * Check for overflow of 8byte PRI READ_KEYS payload and
                 * next reservation key list descriptor.
                 */
                if (off + 8 <= cmd->data_length) {
                        put_unaligned_be64(pr_reg->pr_res_key, &buf[off]);
                        off += 8;
                }
                /*
                 * SPC5r17: 6.16.2 READ KEYS service action
                 * The ADDITIONAL LENGTH field indicates the number of bytes in
                 * the Reservation key list. The contents of the ADDITIONAL
                 * LENGTH field are not altered based on the allocation length
                 */
                add_len += 8;
        }
        spin_unlock(&dev->t10_pr.registration_lock);

        put_unaligned_be32(add_len, &buf[4]);
        target_set_cmd_data_length(cmd, 8 + add_len);

        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 sense_reason_t
core_scsi3_pri_read_reservation(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct t10_pr_registration *pr_reg;
        unsigned char *buf;
        u64 pr_res_key;
        u32 add_len = 0;

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

        buf = transport_kmap_data_sg(cmd);
        if (!buf)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        put_unaligned_be32(dev->t10_pr.pr_generation, &buf[0]);

        spin_lock(&dev->dev_reservation_lock);
        pr_reg = dev->dev_pr_res_holder;
        if (pr_reg) {
                /*
                 * Set the Additional Length to 16 when a reservation is held
                 */
                add_len = 16;
                put_unaligned_be32(add_len, &buf[4]);

                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;

                put_unaligned_be64(pr_res_key, &buf[8]);
                /*
                 * Set the SCOPE and TYPE
                 */
                buf[21] = (pr_reg->pr_res_scope & 0xf0) |
                          (pr_reg->pr_res_type & 0x0f);
        }

        target_set_cmd_data_length(cmd, 8 + add_len);

err:
        spin_unlock(&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 sense_reason_t
core_scsi3_pri_report_capabilities(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct t10_reservation *pr_tmpl = &dev->t10_pr;
        unsigned char *buf;
        u16 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);
                return TCM_INVALID_CDB_FIELD;
        }

        buf = transport_kmap_data_sg(cmd);
        if (!buf)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        put_unaligned_be16(len, &buf[0]);
        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 */

        target_set_cmd_data_length(cmd, len);

        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 sense_reason_t
core_scsi3_pri_read_full_status(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct se_node_acl *se_nacl;
        struct se_portal_group *se_tpg;
        struct t10_pr_registration *pr_reg, *pr_reg_tmp;
        struct t10_reservation *pr_tmpl = &dev->t10_pr;
        unsigned char *buf;
        u32 add_desc_len = 0, add_len = 0;
        u32 off = 8; /* off into first Full Status descriptor */
        int format_code = 0, pr_res_type = 0, pr_res_scope = 0;
        int exp_desc_len, desc_len;
        bool all_reg = false;

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

        buf = transport_kmap_data_sg(cmd);
        if (!buf)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        put_unaligned_be32(dev->t10_pr.pr_generation, &buf[0]);

        spin_lock(&dev->dev_reservation_lock);
        if (dev->dev_pr_res_holder) {
                struct t10_pr_registration *pr_holder = dev->dev_pr_res_holder;

                if (pr_holder->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_ALLREG ||
                    pr_holder->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_ALLREG) {
                        all_reg = true;
                        pr_res_type = pr_holder->pr_res_type;
                        pr_res_scope = pr_holder->pr_res_scope;
                }
        }
        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) {

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

                atomic_inc_mb(&pr_reg->pr_res_holders);
                spin_unlock(&pr_tmpl->registration_lock);
                /*
                 * Determine expected length of $FABRIC_MOD specific
                 * TransportID full status descriptor..
                 */
                exp_desc_len = target_get_pr_transport_id_len(se_nacl, pr_reg,
                                        &format_code);
                if (exp_desc_len < 0 ||
                    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_mb(&pr_reg->pr_res_holders);
                        break;
                }
                /*
                 * Set RESERVATION KEY
                 */
                put_unaligned_be64(pr_reg->pr_res_key, &buf[off]);
                off += 8;
                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 or there is an All Registrants reservation
                 * active, 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 if (all_reg) {
                        buf[off++] |= 0x01;
                        buf[off++] = (pr_res_scope & 0xf0) |
                                     (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) {
                        u16 sep_rtpi = pr_reg->tg_pt_sep_rtpi;

                        put_unaligned_be16(sep_rtpi, &buf[off]);
                        off += 2;
                } else
                        off += 2; /* Skip over RELATIVE TARGET PORT IDENTIFIER */

                buf[off+4] = se_tpg->proto_id;

                /*
                 * Now, have the $FABRIC_MOD fill in the transport ID.
                 */
                desc_len = target_get_pr_transport_id(se_nacl, pr_reg,
                                &format_code, &buf[off+4]);