/*******************************************************************************
 * Filename:  target_core_tpg.c
 *
 * This file contains generic Target Portal Group related functions.
 *
 * (c) Copyright 2002-2013 Datera, Inc.
 *
 * Nicholas A. Bellinger <nab@kernel.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 ******************************************************************************/

#include <linux/net.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/in.h>
#include <linux/export.h>
#include <net/sock.h>
#include <net/tcp.h>
#include <scsi/scsi_proto.h>

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

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

extern struct se_device *g_lun0_dev;

static DEFINE_SPINLOCK(tpg_lock);
static LIST_HEAD(tpg_list);

/*      __core_tpg_get_initiator_node_acl():
 *
 *      mutex_lock(&tpg->acl_node_mutex); must be held when calling
 */
struct se_node_acl *__core_tpg_get_initiator_node_acl(
        struct se_portal_group *tpg,
        const char *initiatorname)
{
        struct se_node_acl *acl;

        list_for_each_entry(acl, &tpg->acl_node_list, acl_list) {
                if (!strcmp(acl->initiatorname, initiatorname))
                        return acl;
        }

        return NULL;
}

/*      core_tpg_get_initiator_node_acl():
 *
 *
 */
struct se_node_acl *core_tpg_get_initiator_node_acl(
        struct se_portal_group *tpg,
        unsigned char *initiatorname)
{
        struct se_node_acl *acl;
        /*
         * Obtain se_node_acl->acl_kref using fabric driver provided
         * initiatorname[] during node acl endpoint lookup driven by
         * new se_session login.
         *
         * The reference is held until se_session shutdown -> release
         * occurs via fabric driver invoked transport_deregister_session()
         * or transport_free_session() code.
         */
        mutex_lock(&tpg->acl_node_mutex);
        acl = __core_tpg_get_initiator_node_acl(tpg, initiatorname);
        if (acl) {
                if (!kref_get_unless_zero(&acl->acl_kref))
                        acl = NULL;
        }
        mutex_unlock(&tpg->acl_node_mutex);

        return acl;
}
EXPORT_SYMBOL(core_tpg_get_initiator_node_acl);

void core_allocate_nexus_loss_ua(
        struct se_node_acl *nacl)
{
        struct se_dev_entry *deve;

        if (!nacl)
                return;

        rcu_read_lock();
        hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link)
                core_scsi3_ua_allocate(deve, 0x29,
                        ASCQ_29H_NEXUS_LOSS_OCCURRED);
        rcu_read_unlock();
}
EXPORT_SYMBOL(core_allocate_nexus_loss_ua);

/*      core_tpg_add_node_to_devs():
 *
 *
 */
void core_tpg_add_node_to_devs(
        struct se_node_acl *acl,
        struct se_portal_group *tpg,
        struct se_lun *lun_orig)
{
        bool lun_access_ro = true;
        struct se_lun *lun;
        struct se_device *dev;

        mutex_lock(&tpg->tpg_lun_mutex);
        hlist_for_each_entry_rcu(lun, &tpg->tpg_lun_hlist, link) {
                if (lun_orig && lun != lun_orig)
                        continue;

                dev = rcu_dereference_check(lun->lun_se_dev,
                                            lockdep_is_held(&tpg->tpg_lun_mutex));
                /*
                 * By default in LIO-Target $FABRIC_MOD,
                 * demo_mode_write_protect is ON, or READ_ONLY;
                 */
                if (!tpg->se_tpg_tfo->tpg_check_demo_mode_write_protect(tpg)) {
                        lun_access_ro = false;
                } else {
                        /*
                         * Allow only optical drives to issue R/W in default RO
                         * demo mode.
                         */
                        if (dev->transport->get_device_type(dev) == TYPE_DISK)
                                lun_access_ro = true;
                        else
                                lun_access_ro = false;
                }

                pr_debug("TARGET_CORE[%s]->TPG[%u]_LUN[%llu] - Adding %s"
                        " access for LUN in Demo Mode\n",
                        tpg->se_tpg_tfo->get_fabric_name(),
                        tpg->se_tpg_tfo->tpg_get_tag(tpg), lun->unpacked_lun,
                        lun_access_ro ? "READ-ONLY" : "READ-WRITE");

                core_enable_device_list_for_node(lun, NULL, lun->unpacked_lun,
                                                 lun_access_ro, acl, tpg);
                /*
                 * Check to see if there are any existing persistent reservation
                 * APTPL pre-registrations that need to be enabled for this dynamic
                 * LUN ACL now..
                 */
                core_scsi3_check_aptpl_registration(dev, tpg, lun, acl,
                                                    lun->unpacked_lun);
        }
        mutex_unlock(&tpg->tpg_lun_mutex);
}

static void
target_set_nacl_queue_depth(struct se_portal_group *tpg,
                            struct se_node_acl *acl, u32 queue_depth)
{
        acl->queue_depth = queue_depth;

        if (!acl->queue_depth) {
                pr_warn("Queue depth for %s Initiator Node: %s is 0,"
                        "defaulting to 1.\n", tpg->se_tpg_tfo->get_fabric_name(),
                        acl->initiatorname);
                acl->queue_depth = 1;
        }
}

static struct se_node_acl *target_alloc_node_acl(struct se_portal_group *tpg,
                const unsigned char *initiatorname)
{
        struct se_node_acl *acl;
        u32 queue_depth;

        acl = kzalloc(max(sizeof(*acl), tpg->se_tpg_tfo->node_acl_size),
                        GFP_KERNEL);
        if (!acl)
                return NULL;

        INIT_LIST_HEAD(&acl->acl_list);
        INIT_LIST_HEAD(&acl->acl_sess_list);
        INIT_HLIST_HEAD(&acl->lun_entry_hlist);
        kref_init(&acl->acl_kref);
        init_completion(&acl->acl_free_comp);
        spin_lock_init(&acl->nacl_sess_lock);
        mutex_init(&acl->lun_entry_mutex);
        atomic_set(&acl->acl_pr_ref_count, 0);

        if (tpg->se_tpg_tfo->tpg_get_default_depth)
                queue_depth = tpg->se_tpg_tfo->tpg_get_default_depth(tpg);
        else
                queue_depth = 1;
        target_set_nacl_queue_depth(tpg, acl, queue_depth);

        snprintf(acl->initiatorname, TRANSPORT_IQN_LEN, "%s", initiatorname);
        acl->se_tpg = tpg;
        acl->acl_index = scsi_get_new_index(SCSI_AUTH_INTR_INDEX);

        tpg->se_tpg_tfo->set_default_node_attributes(acl);

        return acl;
}

static void target_add_node_acl(struct se_node_acl *acl)
{
        struct se_portal_group *tpg = acl->se_tpg;

        mutex_lock(&tpg->acl_node_mutex);
        list_add_tail(&acl->acl_list, &tpg->acl_node_list);
        mutex_unlock(&tpg->acl_node_mutex);

        pr_debug("%s_TPG[%hu] - Added %s ACL with TCQ Depth: %d for %s"
                " Initiator Node: %s\n",
                tpg->se_tpg_tfo->get_fabric_name(),
                tpg->se_tpg_tfo->tpg_get_tag(tpg),
                acl->dynamic_node_acl ? "DYNAMIC" : "",
                acl->queue_depth,
                tpg->se_tpg_tfo->get_fabric_name(),
                acl->initiatorname);
}

bool target_tpg_has_node_acl(struct se_portal_group *tpg,
                             const char *initiatorname)
{
        struct se_node_acl *acl;
        bool found = false;

        mutex_lock(&tpg->acl_node_mutex);
        list_for_each_entry(acl, &tpg->acl_node_list, acl_list) {
                if (!strcmp(acl->initiatorname, initiatorname)) {
                        found = true;
                        break;
                }
        }
        mutex_unlock(&tpg->acl_node_mutex);

        return found;
}
EXPORT_SYMBOL(target_tpg_has_node_acl);

struct se_node_acl *core_tpg_check_initiator_node_acl(
        struct se_portal_group *tpg,
        unsigned char *initiatorname)
{
        struct se_node_acl *acl;

        acl = core_tpg_get_initiator_node_acl(tpg, initiatorname);
        if (acl)
                return acl;

        if (!tpg->se_tpg_tfo->tpg_check_demo_mode(tpg))
                return NULL;

        acl = target_alloc_node_acl(tpg, initiatorname);
        if (!acl)
                return NULL;
        /*
         * When allocating a dynamically generated node_acl, go ahead
         * and take the extra kref now before returning to the fabric
         * driver caller.
         *
         * Note this reference will be released at session shutdown
         * time within transport_free_session() code.
         */
        kref_get(&acl->acl_kref);
        acl->dynamic_node_acl = 1;

        /*
         * Here we only create demo-mode MappedLUNs from the active
         * TPG LUNs if the fabric is not explicitly asking for
         * tpg_check_demo_mode_login_only() == 1.
         */
        if ((tpg->se_tpg_tfo->tpg_check_demo_mode_login_only == NULL) ||
            (tpg->se_tpg_tfo->tpg_check_demo_mode_login_only(tpg) != 1))
                core_tpg_add_node_to_devs(acl, tpg, NULL);

        target_add_node_acl(acl);
        return acl;
}
EXPORT_SYMBOL(core_tpg_check_initiator_node_acl);

void core_tpg_wait_for_nacl_pr_ref(struct se_node_acl *nacl)
{
        while (atomic_read(&nacl->acl_pr_ref_count) != 0)
                cpu_relax();
}

struct se_node_acl *core_tpg_add_initiator_node_acl(
        struct se_portal_group *tpg,
        const char *initiatorname)
{
        struct se_node_acl *acl;

        mutex_lock(&tpg->acl_node_mutex);
        acl = __core_tpg_get_initiator_node_acl(tpg, initiatorname);
        if (acl) {
                if (acl->dynamic_node_acl) {
                        acl->dynamic_node_acl = 0;
                        pr_debug("%s_TPG[%u] - Replacing dynamic ACL"
                                " for %s\n", tpg->se_tpg_tfo->get_fabric_name(),
                                tpg->se_tpg_tfo->tpg_get_tag(tpg), initiatorname);
                        mutex_unlock(&tpg->acl_node_mutex);
                        return acl;
                }

                pr_err("ACL entry for %s Initiator"
                        " Node %s already exists for TPG %u, ignoring"
                        " request.\n",  tpg->se_tpg_tfo->get_fabric_name(),
                        initiatorname, tpg->se_tpg_tfo->tpg_get_tag(tpg));
                mutex_unlock(&tpg->acl_node_mutex);
                return ERR_PTR(-EEXIST);
        }
        mutex_unlock(&tpg->acl_node_mutex);

        acl = target_alloc_node_acl(tpg, initiatorname);
        if (!acl)
                return ERR_PTR(-ENOMEM);

        target_add_node_acl(acl);
        return acl;
}

void core_tpg_del_initiator_node_acl(struct se_node_acl *acl)
{
        struct se_portal_group *tpg = acl->se_tpg;
        LIST_HEAD(sess_list);
        struct se_session *sess, *sess_tmp;
        unsigned long flags;
        int rc;

        mutex_lock(&tpg->acl_node_mutex);
        if (acl->dynamic_node_acl) {
                acl->dynamic_node_acl = 0;
        }
        list_del(&acl->acl_list);
        mutex_unlock(&tpg->acl_node_mutex);

        spin_lock_irqsave(&acl->nacl_sess_lock, flags);
        acl->acl_stop = 1;

        list_for_each_entry_safe(sess, sess_tmp, &acl->acl_sess_list,
                                sess_acl_list) {
                if (sess->sess_tearing_down != 0)
                        continue;

                if (!target_get_session(sess))
                        continue;
                list_move(&sess->sess_acl_list, &sess_list);
        }
        spin_unlock_irqrestore(&acl->nacl_sess_lock, flags);

        list_for_each_entry_safe(sess, sess_tmp, &sess_list, sess_acl_list) {
                list_del(&sess->sess_acl_list);

                rc = tpg->se_tpg_tfo->shutdown_session(sess);
                target_put_session(sess);
                if (!rc)
                        continue;
                target_put_session(sess);
        }
        target_put_nacl(acl);
        /*
         * Wait for last target_put_nacl() to complete in target_complete_nacl()
         * for active fabric session transport_deregister_session() callbacks.
         */
        wait_for_completion(&acl->acl_free_comp);

        core_tpg_wait_for_nacl_pr_ref(acl);
        core_free_device_list_for_node(acl, tpg);

        pr_debug("%s_TPG[%hu] - Deleted ACL with TCQ Depth: %d for %s"
                " Initiator Node: %s\n", tpg->se_tpg_tfo->get_fabric_name(),
                tpg->se_tpg_tfo->tpg_get_tag(tpg), acl->queue_depth,
                tpg->se_tpg_tfo->get_fabric_name(), acl->initiatorname);

        kfree(acl);
}

/*      core_tpg_set_initiator_node_queue_depth():
 *
 *
 */
int core_tpg_set_initiator_node_queue_depth(
        struct se_node_acl *acl,
        u32 queue_depth)
{
        LIST_HEAD(sess_list);
        struct se_portal_group *tpg = acl->se_tpg;
        struct se_session *sess, *sess_tmp;
        unsigned long flags;
        int rc;

        /*
         * User has requested to change the queue depth for a Initiator Node.
         * Change the value in the Node's struct se_node_acl, and call
         * target_set_nacl_queue_depth() to set the new queue depth.
         */
        target_set_nacl_queue_depth(tpg, acl, queue_depth);

        spin_lock_irqsave(&acl->nacl_sess_lock, flags);
        list_for_each_entry_safe(sess, sess_tmp, &acl->acl_sess_list,
                                 sess_acl_list) {
                if (sess->sess_tearing_down != 0)
                        continue;
                if (!target_get_session(sess))
                        continue;
                spin_unlock_irqrestore(&acl->nacl_sess_lock, flags);

                /*
                 * Finally call tpg->se_tpg_tfo->close_session() to force session
                 * reinstatement to occur if there is an active session for the
                 * $FABRIC_MOD Initiator Node in question.
                 */
                rc = tpg->se_tpg_tfo->shutdown_session(sess);
                target_put_session(sess);
                if (!rc) {
                        spin_lock_irqsave(&acl->nacl_sess_lock, flags);
                        continue;
                }
                target_put_session(sess);
                spin_lock_irqsave(&acl->nacl_sess_lock, flags);
        }
        spin_unlock_irqrestore(&acl->nacl_sess_lock, flags);

        pr_debug("Successfully changed queue depth to: %d for Initiator"
                " Node: %s on %s Target Portal Group: %u\n", acl->queue_depth,
                acl->initiatorname, tpg->se_tpg_tfo->get_fabric_name(),
                tpg->se_tpg_tfo->tpg_get_tag(tpg));

        return 0;
}
EXPORT_SYMBOL(core_tpg_set_initiator_node_queue_depth);

/*      core_tpg_set_initiator_node_tag():
 *
 *      Initiator nodeacl tags are not used internally, but may be used by
 *      userspace to emulate aliases or groups.
 *      Returns length of newly-set tag or -EINVAL.
 */
int core_tpg_set_initiator_node_tag(
        struct se_portal_group *tpg,
        struct se_node_acl *acl,
        const char *new_tag)
{
        if (strlen(new_tag) >= MAX_ACL_TAG_SIZE)
                return -EINVAL;

        if (!strncmp("NULL", new_tag, 4)) {
                acl->acl_tag[0] = '\0';
                return 0;
        }

        return snprintf(acl->acl_tag, MAX_ACL_TAG_SIZE, "%s", new_tag);
}
EXPORT_SYMBOL(core_tpg_set_initiator_node_tag);

static void core_tpg_lun_ref_release(struct percpu_ref *ref)
{
        struct se_lun *lun = container_of(ref, struct se_lun, lun_ref);

        complete(&lun->lun_ref_comp);
}

int core_tpg_register(
        struct se_wwn *se_wwn,
        struct se_portal_group *se_tpg,
        int proto_id)
{
        int ret;

        if (!se_tpg)
                return -EINVAL;
        /*
         * For the typical case where core_tpg_register() is called by a
         * fabric driver from target_core_fabric_ops->fabric_make_tpg()
         * configfs context, use the original tf_ops pointer already saved
         * by target-core in target_fabric_make_wwn().
         *
         * Otherwise, for special cases like iscsi-target discovery TPGs
         * the caller is responsible for setting ->se_tpg_tfo ahead of
         * calling core_tpg_register().
         */
        if (se_wwn)
                se_tpg->se_tpg_tfo = se_wwn->wwn_tf->tf_ops;

        if (!se_tpg->se_tpg_tfo) {
                pr_err("Unable to locate se_tpg->se_tpg_tfo pointer\n");
                return -EINVAL;
        }

        INIT_HLIST_HEAD(&se_tpg->tpg_lun_hlist);
        se_tpg->proto_id = proto_id;
        se_tpg->se_tpg_wwn = se_wwn;
        atomic_set(&se_tpg->tpg_pr_ref_count, 0);
        INIT_LIST_HEAD(&se_tpg->acl_node_list);
        INIT_LIST_HEAD(&se_tpg->se_tpg_node);
        INIT_LIST_HEAD(&se_tpg->tpg_sess_list);
        spin_lock_init(&se_tpg->session_lock);
        mutex_init(&se_tpg->tpg_lun_mutex);
        mutex_init(&se_tpg->acl_node_mutex);

        if (se_tpg->proto_id >= 0) {
                se_tpg->tpg_virt_lun0 = core_tpg_alloc_lun(se_tpg, 0);
                if (IS_ERR(se_tpg->tpg_virt_lun0))
                        return PTR_ERR(se_tpg->tpg_virt_lun0);

                ret = core_tpg_add_lun(se_tpg, se_tpg->tpg_virt_lun0,
                                true, g_lun0_dev);
                if (ret < 0) {
                        kfree(se_tpg->tpg_virt_lun0);
                        return ret;
                }
        }

        spin_lock_bh(&tpg_lock);
        list_add_tail(&se_tpg->se_tpg_node, &tpg_list);
        spin_unlock_bh(&tpg_lock);

        pr_debug("TARGET_CORE[%s]: Allocated portal_group for endpoint: %s, "
                 "Proto: %d, Portal Tag: %u\n", se_tpg->se_tpg_tfo->get_fabric_name(),
                se_tpg->se_tpg_tfo->tpg_get_wwn(se_tpg) ?
                se_tpg->se_tpg_tfo->tpg_get_wwn(se_tpg) : NULL,
                se_tpg->proto_id, se_tpg->se_tpg_tfo->tpg_get_tag(se_tpg));

        return 0;
}
EXPORT_SYMBOL(core_tpg_register);

int core_tpg_deregister(struct se_portal_group *se_tpg)
{
        const struct target_core_fabric_ops *tfo = se_tpg->se_tpg_tfo;
        struct se_node_acl *nacl, *nacl_tmp;
        LIST_HEAD(node_list);

        pr_debug("TARGET_CORE[%s]: Deallocating portal_group for endpoint: %s, "
                 "Proto: %d, Portal Tag: %u\n", tfo->get_fabric_name(),
                tfo->tpg_get_wwn(se_tpg) ? tfo->tpg_get_wwn(se_tpg) : NULL,
                se_tpg->proto_id, tfo->tpg_get_tag(se_tpg));

        spin_lock_bh(&tpg_lock);
        list_del(&se_tpg->se_tpg_node);
        spin_unlock_bh(&tpg_lock);

        while (atomic_read(&se_tpg->tpg_pr_ref_count) != 0)
                cpu_relax();

        mutex_lock(&se_tpg->acl_node_mutex);
        list_splice_init(&se_tpg->acl_node_list, &node_list);
        mutex_unlock(&se_tpg->acl_node_mutex);
        /*
         * Release any remaining demo-mode generated se_node_acl that have
         * not been released because of TFO->tpg_check_demo_mode_cache() == 1
         * in transport_deregister_session().
         */
        list_for_each_entry_safe(nacl, nacl_tmp, &node_list, acl_list) {
                list_del(&nacl->acl_list);

                core_tpg_wait_for_nacl_pr_ref(nacl);
                core_free_device_list_for_node(nacl, se_tpg);
                kfree(nacl);
        }

        if (se_tpg->proto_id >= 0) {
                core_tpg_remove_lun(se_tpg, se_tpg->tpg_virt_lun0);
                kfree_rcu(se_tpg->tpg_virt_lun0, rcu_head);
        }

        return 0;
}
EXPORT_SYMBOL(core_tpg_deregister);

struct se_lun *core_tpg_alloc_lun(
        struct se_portal_group *tpg,
        u64 unpacked_lun)
{
        struct se_lun *lun;

        lun = kzalloc(sizeof(*lun), GFP_KERNEL);
        if (!lun) {
                pr_err("Unable to allocate se_lun memory\n");
                return ERR_PTR(-ENOMEM);
        }
        lun->unpacked_lun = unpacked_lun;
        lun->lun_link_magic = SE_LUN_LINK_MAGIC;
        atomic_set(&lun->lun_acl_count, 0);
        init_completion(&lun->lun_ref_comp);
        INIT_LIST_HEAD(&lun->lun_deve_list);
        INIT_LIST_HEAD(&lun->lun_dev_link);
        atomic_set(&lun->lun_tg_pt_secondary_offline, 0);
        spin_lock_init(&lun->lun_deve_lock);
        mutex_init(&lun->lun_tg_pt_md_mutex);
        INIT_LIST_HEAD(&lun->lun_tg_pt_gp_link);
        spin_lock_init(&lun->lun_tg_pt_gp_lock);
        lun->lun_tpg = tpg;

        return lun;
}

int core_tpg_add_lun(
        struct se_portal_group *tpg,
        struct se_lun *lun,
        bool lun_access_ro,
        struct se_device *dev)
{
        int ret;

        ret = percpu_ref_init(&lun->lun_ref, core_tpg_lun_ref_release, 0,
                              GFP_KERNEL);
        if (ret < 0)
                goto out;

        ret = core_alloc_rtpi(lun, dev);
        if (ret)
                goto out_kill_ref;

        if (!(dev->transport->transport_flags & TRANSPORT_FLAG_PASSTHROUGH) &&
            !(dev->se_hba->hba_flags & HBA_FLAGS_INTERNAL_USE))
                target_attach_tg_pt_gp(lun, dev->t10_alua.default_tg_pt_gp);

        mutex_lock(&tpg->tpg_lun_mutex);

        spin_lock(&dev->se_port_lock);
        lun->lun_index = dev->dev_index;
        rcu_assign_pointer(lun->lun_se_dev, dev);
        dev->export_count++;
        list_add_tail(&lun->lun_dev_link, &dev->dev_sep_list);
        spin_unlock(&dev->se_port_lock);

        if (dev->dev_flags & DF_READ_ONLY)
                lun->lun_access_ro = true;
        else
                lun->lun_access_ro = lun_access_ro;
        if (!(dev->se_hba->hba_flags & HBA_FLAGS_INTERNAL_USE))
                hlist_add_head_rcu(&lun->link, &tpg->tpg_lun_hlist);
        mutex_unlock(&tpg->tpg_lun_mutex);

        return 0;

out_kill_ref:
        percpu_ref_exit(&lun->lun_ref);
out:
        return ret;
}

void core_tpg_remove_lun(
        struct se_portal_group *tpg,
        struct se_lun *lun)
{
        /*
         * rcu_dereference_raw protected by se_lun->lun_group symlink
         * reference to se_device->dev_group.
         */
        struct se_device *dev = rcu_dereference_raw(lun->lun_se_dev);

        core_clear_lun_from_tpg(lun, tpg);
        /*
         * Wait for any active I/O references to percpu se_lun->lun_ref to
         * be released.  Also, se_lun->lun_ref is now used by PR and ALUA
         * logic when referencing a remote target port during ALL_TGT_PT=1
         * and generating UNIT_ATTENTIONs for ALUA access state transition.
         */
        transport_clear_lun_ref(lun);

        mutex_lock(&tpg->tpg_lun_mutex);
        if (lun->lun_se_dev) {
                target_detach_tg_pt_gp(lun);

                spin_lock(&dev->se_port_lock);
                list_del(&lun->lun_dev_link);
                dev->export_count--;
                rcu_assign_pointer(lun->lun_se_dev, NULL);
                spin_unlock(&dev->se_port_lock);
        }
        if (!(dev->se_hba->hba_flags & HBA_FLAGS_INTERNAL_USE))
                hlist_del_rcu(&lun->link);
        mutex_unlock(&tpg->tpg_lun_mutex);

        percpu_ref_exit(&lun->lun_ref);
}