/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * 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 version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2015, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/obdclass/genops.c
 *
 * These are the only exported functions, they provide some generic
 * infrastructure for managing object devices
 */

#define DEBUG_SUBSYSTEM S_CLASS
#include "../include/obd_class.h"
#include "../include/lprocfs_status.h"
#include "../include/lustre_kernelcomm.h"

spinlock_t obd_types_lock;

static struct kmem_cache *obd_device_cachep;
struct kmem_cache *obdo_cachep;
EXPORT_SYMBOL(obdo_cachep);
static struct kmem_cache *import_cachep;

static struct list_head      obd_zombie_imports;
static struct list_head      obd_zombie_exports;
static spinlock_t  obd_zombie_impexp_lock;
static void obd_zombie_impexp_notify(void);
static void obd_zombie_export_add(struct obd_export *exp);
static void obd_zombie_import_add(struct obd_import *imp);

int (*ptlrpc_put_connection_superhack)(struct ptlrpc_connection *c);
EXPORT_SYMBOL(ptlrpc_put_connection_superhack);

/*
 * support functions: we could use inter-module communication, but this
 * is more portable to other OS's
 */
static struct obd_device *obd_device_alloc(void)
{
        struct obd_device *obd;

        obd = kmem_cache_zalloc(obd_device_cachep, GFP_NOFS);
        if (obd)
                obd->obd_magic = OBD_DEVICE_MAGIC;
        return obd;
}

static void obd_device_free(struct obd_device *obd)
{
        LASSERTF(obd->obd_magic == OBD_DEVICE_MAGIC, "obd %p obd_magic %08x != %08x\n",
                 obd, obd->obd_magic, OBD_DEVICE_MAGIC);
        if (obd->obd_namespace) {
                CERROR("obd %p: namespace %p was not properly cleaned up (obd_force=%d)!\n",
                       obd, obd->obd_namespace, obd->obd_force);
                LBUG();
        }
        lu_ref_fini(&obd->obd_reference);
        kmem_cache_free(obd_device_cachep, obd);
}

static struct obd_type *class_search_type(const char *name)
{
        struct list_head *tmp;
        struct obd_type *type;

        spin_lock(&obd_types_lock);
        list_for_each(tmp, &obd_types) {
                type = list_entry(tmp, struct obd_type, typ_chain);
                if (strcmp(type->typ_name, name) == 0) {
                        spin_unlock(&obd_types_lock);
                        return type;
                }
        }
        spin_unlock(&obd_types_lock);
        return NULL;
}

static struct obd_type *class_get_type(const char *name)
{
        struct obd_type *type = class_search_type(name);

        if (!type) {
                const char *modname = name;

                if (!request_module("%s", modname)) {
                        CDEBUG(D_INFO, "Loaded module '%s'\n", modname);
                        type = class_search_type(name);
                } else {
                        LCONSOLE_ERROR_MSG(0x158, "Can't load module '%s'\n",
                                           modname);
                }
        }
        if (type) {
                spin_lock(&type->obd_type_lock);
                type->typ_refcnt++;
                try_module_get(type->typ_dt_ops->owner);
                spin_unlock(&type->obd_type_lock);
        }
        return type;
}

void class_put_type(struct obd_type *type)
{
        LASSERT(type);
        spin_lock(&type->obd_type_lock);
        type->typ_refcnt--;
        module_put(type->typ_dt_ops->owner);
        spin_unlock(&type->obd_type_lock);
}
EXPORT_SYMBOL(class_put_type);

#define CLASS_MAX_NAME 1024

int class_register_type(struct obd_ops *dt_ops, struct md_ops *md_ops,
                        const char *name,
                        struct lu_device_type *ldt)
{
        struct obd_type *type;
        int rc;

        /* sanity check */
        LASSERT(strnlen(name, CLASS_MAX_NAME) < CLASS_MAX_NAME);

        if (class_search_type(name)) {
                CDEBUG(D_IOCTL, "Type %s already registered\n", name);
                return -EEXIST;
        }

        rc = -ENOMEM;
        type = kzalloc(sizeof(*type), GFP_NOFS);
        if (!type)
                return rc;

        type->typ_dt_ops = kzalloc(sizeof(*type->typ_dt_ops), GFP_NOFS);
        type->typ_md_ops = kzalloc(sizeof(*type->typ_md_ops), GFP_NOFS);
        type->typ_name = kzalloc(strlen(name) + 1, GFP_NOFS);

        if (!type->typ_dt_ops ||
            !type->typ_md_ops ||
            !type->typ_name)
                goto failed;

        *(type->typ_dt_ops) = *dt_ops;
        /* md_ops is optional */
        if (md_ops)
                *(type->typ_md_ops) = *md_ops;
        strcpy(type->typ_name, name);
        spin_lock_init(&type->obd_type_lock);

        type->typ_debugfs_entry = ldebugfs_register(type->typ_name,
                                                    debugfs_lustre_root,
                                                    NULL, type);
        if (IS_ERR_OR_NULL(type->typ_debugfs_entry)) {
                rc = type->typ_debugfs_entry ? PTR_ERR(type->typ_debugfs_entry)
                                             : -ENOMEM;
                type->typ_debugfs_entry = NULL;
                goto failed;
        }

        type->typ_kobj = kobject_create_and_add(type->typ_name, lustre_kobj);
        if (!type->typ_kobj) {
                rc = -ENOMEM;
                goto failed;
        }

        if (ldt) {
                type->typ_lu = ldt;
                rc = lu_device_type_init(ldt);
                if (rc != 0)
                        goto failed;
        }

        spin_lock(&obd_types_lock);
        list_add(&type->typ_chain, &obd_types);
        spin_unlock(&obd_types_lock);

        return 0;

 failed:
        if (type->typ_kobj)
                kobject_put(type->typ_kobj);
        kfree(type->typ_name);
        kfree(type->typ_md_ops);
        kfree(type->typ_dt_ops);
        kfree(type);
        return rc;
}
EXPORT_SYMBOL(class_register_type);

int class_unregister_type(const char *name)
{
        struct obd_type *type = class_search_type(name);

        if (!type) {
                CERROR("unknown obd type\n");
                return -EINVAL;
        }

        if (type->typ_refcnt) {
                CERROR("type %s has refcount (%d)\n", name, type->typ_refcnt);
                /* This is a bad situation, let's make the best of it */
                /* Remove ops, but leave the name for debugging */
                kfree(type->typ_dt_ops);
                kfree(type->typ_md_ops);
                return -EBUSY;
        }

        if (type->typ_kobj)
                kobject_put(type->typ_kobj);

        if (!IS_ERR_OR_NULL(type->typ_debugfs_entry))
                ldebugfs_remove(&type->typ_debugfs_entry);

        if (type->typ_lu)
                lu_device_type_fini(type->typ_lu);

        spin_lock(&obd_types_lock);
        list_del(&type->typ_chain);
        spin_unlock(&obd_types_lock);
        kfree(type->typ_name);
        kfree(type->typ_dt_ops);
        kfree(type->typ_md_ops);
        kfree(type);
        return 0;
} /* class_unregister_type */
EXPORT_SYMBOL(class_unregister_type);

/**
 * Create a new obd device.
 *
 * Find an empty slot in ::obd_devs[], create a new obd device in it.
 *
 * \param[in] type_name obd device type string.
 * \param[in] name      obd device name.
 *
 * \retval NULL if create fails, otherwise return the obd device
 *       pointer created.
 */
struct obd_device *class_newdev(const char *type_name, const char *name)
{
        struct obd_device *result = NULL;
        struct obd_device *newdev;
        struct obd_type *type = NULL;
        int i;
        int new_obd_minor = 0;

        if (strlen(name) >= MAX_OBD_NAME) {
                CERROR("name/uuid must be < %u bytes long\n", MAX_OBD_NAME);
                return ERR_PTR(-EINVAL);
        }

        type = class_get_type(type_name);
        if (!type) {
                CERROR("OBD: unknown type: %s\n", type_name);
                return ERR_PTR(-ENODEV);
        }

        newdev = obd_device_alloc();
        if (!newdev) {
                result = ERR_PTR(-ENOMEM);
                goto out_type;
        }

        LASSERT(newdev->obd_magic == OBD_DEVICE_MAGIC);

        write_lock(&obd_dev_lock);
        for (i = 0; i < class_devno_max(); i++) {
                struct obd_device *obd = class_num2obd(i);

                if (obd && (strcmp(name, obd->obd_name) == 0)) {
                        CERROR("Device %s already exists at %d, won't add\n",
                               name, i);
                        if (result) {
                                LASSERTF(result->obd_magic == OBD_DEVICE_MAGIC,
                                         "%p obd_magic %08x != %08x\n", result,
                                         result->obd_magic, OBD_DEVICE_MAGIC);
                                LASSERTF(result->obd_minor == new_obd_minor,
                                         "%p obd_minor %d != %d\n", result,
                                         result->obd_minor, new_obd_minor);

                                obd_devs[result->obd_minor] = NULL;
                                result->obd_name[0] = '\0';
                         }
                        result = ERR_PTR(-EEXIST);
                        break;
                }
                if (!result && !obd) {
                        result = newdev;
                        result->obd_minor = i;
                        new_obd_minor = i;
                        result->obd_type = type;
                        strncpy(result->obd_name, name,
                                sizeof(result->obd_name) - 1);
                        obd_devs[i] = result;
                }
        }
        write_unlock(&obd_dev_lock);

        if (!result && i >= class_devno_max()) {
                CERROR("all %u OBD devices used, increase MAX_OBD_DEVICES\n",
                       class_devno_max());
                result = ERR_PTR(-EOVERFLOW);
                goto out;
        }

        if (IS_ERR(result))
                goto out;

        CDEBUG(D_IOCTL, "Adding new device %s (%p)\n",
               result->obd_name, result);

        return result;
out:
        obd_device_free(newdev);
out_type:
        class_put_type(type);
        return result;
}

void class_release_dev(struct obd_device *obd)
{
        struct obd_type *obd_type = obd->obd_type;

        LASSERTF(obd->obd_magic == OBD_DEVICE_MAGIC, "%p obd_magic %08x != %08x\n",
                 obd, obd->obd_magic, OBD_DEVICE_MAGIC);
        LASSERTF(obd == obd_devs[obd->obd_minor], "obd %p != obd_devs[%d] %p\n",
                 obd, obd->obd_minor, obd_devs[obd->obd_minor]);
        LASSERT(obd_type);

        CDEBUG(D_INFO, "Release obd device %s at %d obd_type name =%s\n",
               obd->obd_name, obd->obd_minor, obd->obd_type->typ_name);

        write_lock(&obd_dev_lock);
        obd_devs[obd->obd_minor] = NULL;
        write_unlock(&obd_dev_lock);
        obd_device_free(obd);

        class_put_type(obd_type);
}

int class_name2dev(const char *name)
{
        int i;

        if (!name)
                return -1;

        read_lock(&obd_dev_lock);
        for (i = 0; i < class_devno_max(); i++) {
                struct obd_device *obd = class_num2obd(i);

                if (obd && strcmp(name, obd->obd_name) == 0) {
                        /* Make sure we finished attaching before we give
                         * out any references
                         */
                        LASSERT(obd->obd_magic == OBD_DEVICE_MAGIC);
                        if (obd->obd_attached) {
                                read_unlock(&obd_dev_lock);
                                return i;
                        }
                        break;
                }
        }
        read_unlock(&obd_dev_lock);

        return -1;
}
EXPORT_SYMBOL(class_name2dev);

struct obd_device *class_name2obd(const char *name)
{
        int dev = class_name2dev(name);

        if (dev < 0 || dev > class_devno_max())
                return NULL;
        return class_num2obd(dev);
}
EXPORT_SYMBOL(class_name2obd);

int class_uuid2dev(struct obd_uuid *uuid)
{
        int i;

        read_lock(&obd_dev_lock);
        for (i = 0; i < class_devno_max(); i++) {
                struct obd_device *obd = class_num2obd(i);

                if (obd && obd_uuid_equals(uuid, &obd->obd_uuid)) {
                        LASSERT(obd->obd_magic == OBD_DEVICE_MAGIC);
                        read_unlock(&obd_dev_lock);
                        return i;
                }
        }
        read_unlock(&obd_dev_lock);

        return -1;
}
EXPORT_SYMBOL(class_uuid2dev);

/**
 * Get obd device from ::obd_devs[]
 *
 * \param num [in] array index
 *
 * \retval NULL if ::obd_devs[\a num] does not contains an obd device
 *       otherwise return the obd device there.
 */
struct obd_device *class_num2obd(int num)
{
        struct obd_device *obd = NULL;

        if (num < class_devno_max()) {
                obd = obd_devs[num];
                if (!obd)
                        return NULL;

                LASSERTF(obd->obd_magic == OBD_DEVICE_MAGIC,
                         "%p obd_magic %08x != %08x\n",
                         obd, obd->obd_magic, OBD_DEVICE_MAGIC);
                LASSERTF(obd->obd_minor == num,
                         "%p obd_minor %0d != %0d\n",
                         obd, obd->obd_minor, num);
        }

        return obd;
}
EXPORT_SYMBOL(class_num2obd);

/* Search for a client OBD connected to tgt_uuid.  If grp_uuid is
 * specified, then only the client with that uuid is returned,
 * otherwise any client connected to the tgt is returned.
 */
struct obd_device *class_find_client_obd(struct obd_uuid *tgt_uuid,
                                         const char *typ_name,
                                         struct obd_uuid *grp_uuid)
{
        int i;

        read_lock(&obd_dev_lock);
        for (i = 0; i < class_devno_max(); i++) {
                struct obd_device *obd = class_num2obd(i);

                if (!obd)
                        continue;
                if ((strncmp(obd->obd_type->typ_name, typ_name,
                             strlen(typ_name)) == 0)) {
                        if (obd_uuid_equals(tgt_uuid,
                                            &obd->u.cli.cl_target_uuid) &&
                            ((grp_uuid) ? obd_uuid_equals(grp_uuid,
                                                         &obd->obd_uuid) : 1)) {
                                read_unlock(&obd_dev_lock);
                                return obd;
                        }
                }
        }
        read_unlock(&obd_dev_lock);

        return NULL;
}
EXPORT_SYMBOL(class_find_client_obd);

/* Iterate the obd_device list looking devices have grp_uuid. Start
 * searching at *next, and if a device is found, the next index to look
 * at is saved in *next. If next is NULL, then the first matching device
 * will always be returned.
 */
struct obd_device *class_devices_in_group(struct obd_uuid *grp_uuid, int *next)
{
        int i;

        if (!next)
                i = 0;
        else if (*next >= 0 && *next < class_devno_max())
                i = *next;
        else
                return NULL;

        read_lock(&obd_dev_lock);
        for (; i < class_devno_max(); i++) {
                struct obd_device *obd = class_num2obd(i);

                if (!obd)
                        continue;
                if (obd_uuid_equals(grp_uuid, &obd->obd_uuid)) {
                        if (next)
                                *next = i+1;
                        read_unlock(&obd_dev_lock);
                        return obd;
                }
        }
        read_unlock(&obd_dev_lock);

        return NULL;
}
EXPORT_SYMBOL(class_devices_in_group);

/**
 * to notify sptlrpc log for \a fsname has changed, let every relevant OBD
 * adjust sptlrpc settings accordingly.
 */
int class_notify_sptlrpc_conf(const char *fsname, int namelen)
{
        struct obd_device  *obd;
        const char       *type;
        int              i, rc = 0, rc2;

        LASSERT(namelen > 0);

        read_lock(&obd_dev_lock);
        for (i = 0; i < class_devno_max(); i++) {
                obd = class_num2obd(i);

                if (!obd || obd->obd_set_up == 0 || obd->obd_stopping)
                        continue;

                /* only notify mdc, osc, mdt, ost */
                type = obd->obd_type->typ_name;
                if (strcmp(type, LUSTRE_MDC_NAME) != 0 &&
                    strcmp(type, LUSTRE_OSC_NAME) != 0 &&
                    strcmp(type, LUSTRE_MDT_NAME) != 0 &&
                    strcmp(type, LUSTRE_OST_NAME) != 0)
                        continue;

                if (strncmp(obd->obd_name, fsname, namelen))
                        continue;

                class_incref(obd, __func__, obd);
                read_unlock(&obd_dev_lock);
                rc2 = obd_set_info_async(NULL, obd->obd_self_export,
                                         sizeof(KEY_SPTLRPC_CONF),
                                         KEY_SPTLRPC_CONF, 0, NULL, NULL);
                rc = rc ? rc : rc2;
                class_decref(obd, __func__, obd);
                read_lock(&obd_dev_lock);
        }
        read_unlock(&obd_dev_lock);
        return rc;
}
EXPORT_SYMBOL(class_notify_sptlrpc_conf);

void obd_cleanup_caches(void)
{
        kmem_cache_destroy(obd_device_cachep);
        obd_device_cachep = NULL;
        kmem_cache_destroy(obdo_cachep);
        obdo_cachep = NULL;
        kmem_cache_destroy(import_cachep);
        import_cachep = NULL;
}

int obd_init_caches(void)
{
        LASSERT(!obd_device_cachep);
        obd_device_cachep = kmem_cache_create("ll_obd_dev_cache",
                                              sizeof(struct obd_device),
                                              0, 0, NULL);
        if (!obd_device_cachep)
                goto out;

        LASSERT(!obdo_cachep);
        obdo_cachep = kmem_cache_create("ll_obdo_cache", sizeof(struct obdo),
                                        0, 0, NULL);
        if (!obdo_cachep)
                goto out;

        LASSERT(!import_cachep);
        import_cachep = kmem_cache_create("ll_import_cache",
                                          sizeof(struct obd_import),
                                          0, 0, NULL);
        if (!import_cachep)
                goto out;

        return 0;
 out:
        obd_cleanup_caches();
        return -ENOMEM;
}

/* map connection to client */
struct obd_export *class_conn2export(struct lustre_handle *conn)
{
        struct obd_export *export;

        if (!conn) {
                CDEBUG(D_CACHE, "looking for null handle\n");
                return NULL;
        }

        if (conn->cookie == -1) {  /* this means assign a new connection */
                CDEBUG(D_CACHE, "want a new connection\n");
                return NULL;
        }

        CDEBUG(D_INFO, "looking for export cookie %#llx\n", conn->cookie);
        export = class_handle2object(conn->cookie);
        return export;
}
EXPORT_SYMBOL(class_conn2export);

struct obd_device *class_exp2obd(struct obd_export *exp)
{
        if (exp)
                return exp->exp_obd;
        return NULL;
}
EXPORT_SYMBOL(class_exp2obd);

struct obd_import *class_exp2cliimp(struct obd_export *exp)
{
        struct obd_device *obd = exp->exp_obd;

        if (!obd)
                return NULL;
        return obd->u.cli.cl_import;
}
EXPORT_SYMBOL(class_exp2cliimp);

/* Export management functions */
static void class_export_destroy(struct obd_export *exp)
{
        struct obd_device *obd = exp->exp_obd;

        LASSERT_ATOMIC_ZERO(&exp->exp_refcount);
        LASSERT(obd);

        CDEBUG(D_IOCTL, "destroying export %p/%s for %s\n", exp,
               exp->exp_client_uuid.uuid, obd->obd_name);

        /* "Local" exports (lctl, LOV->{mdc,osc}) have no connection. */
        if (exp->exp_connection)
                ptlrpc_put_connection_superhack(exp->exp_connection);

        LASSERT(list_empty(&exp->exp_outstanding_replies));
        LASSERT(list_empty(&exp->exp_uncommitted_replies));
        LASSERT(list_empty(&exp->exp_req_replay_queue));
        LASSERT(list_empty(&exp->exp_hp_rpcs));
        obd_destroy_export(exp);
        class_decref(obd, "export", exp);

        OBD_FREE_RCU(exp, sizeof(*exp), &exp->exp_handle);
}

static void export_handle_addref(void *export)
{
        class_export_get(export);
}

static struct portals_handle_ops export_handle_ops = {
        .hop_addref = export_handle_addref,
        .hop_free   = NULL,
};

struct obd_export *class_export_get(struct obd_export *exp)
{
        atomic_inc(&exp->exp_refcount);
        CDEBUG(D_INFO, "GETting export %p : new refcount %d\n", exp,
               atomic_read(&exp->exp_refcount));
        return exp;
}
EXPORT_SYMBOL(class_export_get);

void class_export_put(struct obd_export *exp)
{
        LASSERT_ATOMIC_GT_LT(&exp->exp_refcount, 0, LI_POISON);
        CDEBUG(D_INFO, "PUTting export %p : new refcount %d\n", exp,
               atomic_read(&exp->exp_refcount) - 1);

        if (atomic_dec_and_test(&exp->exp_refcount)) {
                LASSERT(!list_empty(&exp->exp_obd_chain));
                CDEBUG(D_IOCTL, "final put %p/%s\n",
                       exp, exp->exp_client_uuid.uuid);

                /* release nid stat refererence */
                lprocfs_exp_cleanup(exp);

                obd_zombie_export_add(exp);
        }
}
EXPORT_SYMBOL(class_export_put);

/* Creates a new export, adds it to the hash table, and returns a
 * pointer to it. The refcount is 2: one for the hash reference, and
 * one for the pointer returned by this function.
 */
struct obd_export *class_new_export(struct obd_device *obd,
                                    struct obd_uuid *cluuid)
{
        struct obd_export *export;
        struct cfs_hash *hash = NULL;
        int rc = 0;

        export = kzalloc(sizeof(*export), GFP_NOFS);
        if (!export)
                return ERR_PTR(-ENOMEM);

        export->exp_conn_cnt = 0;
        export->exp_lock_hash = NULL;
        export->exp_flock_hash = NULL;
        atomic_set(&export->exp_refcount, 2);
        atomic_set(&export->exp_rpc_count, 0);
        atomic_set(&export->exp_cb_count, 0);
        atomic_set(&export->exp_locks_count, 0);
#if LUSTRE_TRACKS_LOCK_EXP_REFS
        INIT_LIST_HEAD(&export->exp_locks_list);
        spin_lock_init(&export->exp_locks_list_guard);
#endif
        atomic_set(&export->exp_replay_count, 0);
        export->exp_obd = obd;
        INIT_LIST_HEAD(&export->exp_outstanding_replies);
        spin_lock_init(&export->exp_uncommitted_replies_lock);
        INIT_LIST_HEAD(&export->exp_uncommitted_replies);
        INIT_LIST_HEAD(&export->exp_req_replay_queue);
        INIT_LIST_HEAD(&export->exp_handle.h_link);
        INIT_LIST_HEAD(&export->exp_hp_rpcs);
        class_handle_hash(&export->exp_handle, &export_handle_ops);
        spin_lock_init(&export->exp_lock);
        spin_lock_init(&export->exp_rpc_lock);
        INIT_HLIST_NODE(&export->exp_uuid_hash);
        spin_lock_init(&export->exp_bl_list_lock);
        INIT_LIST_HEAD(&export->exp_bl_list);

        export->exp_sp_peer = LUSTRE_SP_ANY;
        export->exp_flvr.sf_rpc = SPTLRPC_FLVR_INVALID;
        export->exp_client_uuid = *cluuid;
        obd_init_export(export);

        spin_lock(&obd->obd_dev_lock);
        /* shouldn't happen, but might race */
        if (obd->obd_stopping) {
                rc = -ENODEV;
                goto exit_unlock;
        }

        hash = cfs_hash_getref(obd->obd_uuid_hash);
        if (!hash) {
                rc = -ENODEV;
                goto exit_unlock;
        }
        spin_unlock(&obd->obd_dev_lock);

        if (!obd_uuid_equals(cluuid, &obd->obd_uuid)) {
                rc = cfs_hash_add_unique(hash, cluuid, &export->exp_uuid_hash);
                if (rc != 0) {
                        LCONSOLE_WARN("%s: denying duplicate export for %s, %d\n",
                                      obd->obd_name, cluuid->uuid, rc);
                        rc = -EALREADY;
                        goto exit_err;
                }
        }

        spin_lock(&obd->obd_dev_lock);
        if (obd->obd_stopping) {
                cfs_hash_del(hash, cluuid, &export->exp_uuid_hash);
                rc = -ENODEV;
                goto exit_unlock;
        }

        class_incref(obd, "export", export);
        list_add(&export->exp_obd_chain, &export->exp_obd->obd_exports);
        export->exp_obd->obd_num_exports++;
        spin_unlock(&obd->obd_dev_lock);
        cfs_hash_putref(hash);
        return export;

exit_unlock:
        spin_unlock(&obd->obd_dev_lock);
exit_err:
        if (hash)
                cfs_hash_putref(hash);
        class_handle_unhash(&export->exp_handle);
        LASSERT(hlist_unhashed(&export->exp_uuid_hash));
        obd_destroy_export(export);
        kfree(export);
        return ERR_PTR(rc);
}
EXPORT_SYMBOL(class_new_export);

void class_unlink_export(struct obd_export *exp)
{
        class_handle_unhash(&exp->exp_handle);

        spin_lock(&exp->exp_obd->obd_dev_lock);
        /* delete an uuid-export hashitem from hashtables */
        if (!hlist_unhashed(&exp->exp_uuid_hash))
                cfs_hash_del(exp->exp_obd->obd_uuid_hash,
                             &exp->exp_client_uuid,
                             &exp->exp_uuid_hash);

        list_move(&exp->exp_obd_chain, &exp->exp_obd->obd_unlinked_exports);
        exp->exp_obd->obd_num_exports--;
        spin_unlock(&exp->exp_obd->obd_dev_lock);
        class_export_put(exp);
}
EXPORT_SYMBOL(class_unlink_export);

/* Import management functions */
static void class_import_destroy(struct obd_import *imp)
{
        CDEBUG(D_IOCTL, "destroying import %p for %s\n", imp,
               imp->imp_obd->obd_name);

        LASSERT_ATOMIC_ZERO(&imp->imp_refcount);

        ptlrpc_put_connection_superhack(imp->imp_connection);

        while (!list_empty(&imp->imp_conn_list)) {
                struct obd_import_conn *imp_conn;

                imp_conn = list_entry(imp->imp_conn_list.next,
                                      struct obd_import_conn, oic_item);
                list_del_init(&imp_conn->oic_item);
                ptlrpc_put_connection_superhack(imp_conn->oic_conn);
                kfree(imp_conn);
        }

        LASSERT(!imp->imp_sec);
        class_decref(imp->imp_obd, "import", imp);
        OBD_FREE_RCU(imp, sizeof(*imp), &imp->imp_handle);
}

static void import_handle_addref(void *import)
{
        class_import_get(import);
}

static struct portals_handle_ops import_handle_ops = {
        .hop_addref = import_handle_addref,
        .hop_free   = NULL,
};

struct obd_import *class_import_get(struct obd_import *import)
{
        atomic_inc(&import->imp_refcount);
        CDEBUG(D_INFO, "import %p refcount=%d obd=%s\n", import,
               atomic_read(&import->imp_refcount),
               import->imp_obd->obd_name);
        return import;
}
EXPORT_SYMBOL(class_import_get);

void class_import_put(struct obd_import *imp)
{
        LASSERT(list_empty(&imp->imp_zombie_chain));
        LASSERT_ATOMIC_GT_LT(&imp->imp_refcount, 0, LI_POISON);

        CDEBUG(D_INFO, "import %p refcount=%d obd=%s\n", imp,
               atomic_read(&imp->imp_refcount) - 1,
               imp->imp_obd->obd_name);

        if (atomic_dec_and_test(&imp->imp_refcount)) {
                CDEBUG(D_INFO, "final put import %p\n", imp);
                obd_zombie_import_add(imp);
        }

        /* catch possible import put race */
        LASSERT_ATOMIC_GE_LT(&imp->imp_refcount, 0, LI_POISON);
}
EXPORT_SYMBOL(class_import_put);

static void init_imp_at(struct imp_at *at)
{
        int i;

        at_init(&at->iat_net_latency, 0, 0);
        for (i = 0; i < IMP_AT_MAX_PORTALS; i++) {
                /* max service estimates are tracked on the server side, so
                 * don't use the AT history here, just use the last reported
                 * val. (But keep hist for proc histogram, worst_ever)
                 */
                at_init(&at->iat_service_estimate[i], INITIAL_CONNECT_TIMEOUT,
                        AT_FLG_NOHIST);
        }
}

struct obd_import *class_new_import(struct obd_device *obd)
{
        struct obd_import *imp;

        imp = kzalloc(sizeof(*imp), GFP_NOFS);
        if (!imp)
                return NULL;

        INIT_LIST_HEAD(&imp->imp_pinger_chain);
        INIT_LIST_HEAD(&imp->imp_zombie_chain);
        INIT_LIST_HEAD(&imp->imp_replay_list);
        INIT_LIST_HEAD(&imp->imp_sending_list);
        INIT_LIST_HEAD(&imp->imp_delayed_list);
        INIT_LIST_HEAD(&imp->imp_committed_list);
        imp->imp_replay_cursor = &imp->imp_committed_list;
        spin_lock_init(&imp->imp_lock);
        imp->imp_last_success_conn = 0;
        imp->imp_state = LUSTRE_IMP_NEW;
        imp->imp_obd = class_incref(obd, "import", imp);
        mutex_init(&imp->imp_sec_mutex);
        init_waitqueue_head(&imp->imp_recovery_waitq);

        atomic_set(&imp->imp_refcount, 2);
        atomic_set(&imp->imp_unregistering, 0);
        atomic_set(&imp->imp_inflight, 0);
        atomic_set(&imp->imp_replay_inflight, 0);
        atomic_set(&imp->imp_inval_count, 0);
        INIT_LIST_HEAD(&imp->imp_conn_list);
        INIT_LIST_HEAD(&imp->imp_handle.h_link);
        class_handle_hash(&imp->imp_handle, &import_handle_ops);
        init_imp_at(&imp->imp_at);

        /* the default magic is V2, will be used in connect RPC, and
         * then adjusted according to the flags in request/reply.
         */
        imp->imp_msg_magic = LUSTRE_MSG_MAGIC_V2;

        return imp;
}
EXPORT_SYMBOL(class_new_import);

void class_destroy_import(struct obd_import *import)
{
        LASSERT(import);
        LASSERT(import != LP_POISON);

        class_handle_unhash(&import->imp_handle);

        spin_lock(&import->imp_lock);
        import->imp_generation++;
        spin_unlock(&import->imp_lock);
        class_import_put(import);
}
EXPORT_SYMBOL(class_destroy_import);

#if LUSTRE_TRACKS_LOCK_EXP_REFS

void __class_export_add_lock_ref(struct obd_export *exp, struct ldlm_lock *lock)
{
        spin_lock(&exp->exp_locks_list_guard);

        LASSERT(lock->l_exp_refs_nr >= 0);

        if (lock->l_exp_refs_target && lock->l_exp_refs_target != exp) {
                LCONSOLE_WARN("setting export %p for lock %p which already has export %p\n",
                              exp, lock, lock->l_exp_refs_target);
        }
        if ((lock->l_exp_refs_nr++) == 0) {
                list_add(&lock->l_exp_refs_link, &exp->exp_locks_list);
                lock->l_exp_refs_target = exp;
        }
        CDEBUG(D_INFO, "lock = %p, export = %p, refs = %u\n",
               lock, exp, lock->l_exp_refs_nr);
        spin_unlock(&exp->exp_locks_list_guard);
}
EXPORT_SYMBOL(__class_export_add_lock_ref);

void __class_export_del_lock_ref(struct obd_export *exp, struct ldlm_lock *lock)
{
        spin_lock(&exp->exp_locks_list_guard);
        LASSERT(lock->l_exp_refs_nr > 0);
        if (lock->l_exp_refs_target != exp) {
                LCONSOLE_WARN("lock %p, mismatching export pointers: %p, %p\n",
                              lock, lock->l_exp_refs_target, exp);
        }
        if (-- lock->l_exp_refs_nr == 0) {
                list_del_init(&lock->l_exp_refs_link);
                lock->l_exp_refs_target = NULL;
        }
        CDEBUG(D_INFO, "lock = %p, export = %p, refs = %u\n",
               lock, exp, lock->l_exp_refs_nr);
        spin_unlock(&exp->exp_locks_list_guard);
}
EXPORT_SYMBOL(__class_export_del_lock_ref);
#endif

/* A connection defines an export context in which preallocation can
 * be managed. This releases the export pointer reference, and returns
 * the export handle, so the export refcount is 1 when this function
 * returns.

 */
int class_connect(struct lustre_handle *conn, struct obd_device *obd,
                  struct obd_uuid *cluuid)
{
        struct obd_export *export;

        LASSERT(conn);
        LASSERT(obd);
        LASSERT(cluuid);

        export = class_new_export(obd, cluuid);
        if (IS_ERR(export))
                return PTR_ERR(export);

        conn->cookie = export->exp_handle.h_cookie;
        class_export_put(export);

        CDEBUG(D_IOCTL, "connect: client %s, cookie %#llx\n",
               cluuid->uuid, conn->cookie);
        return 0;
}
EXPORT_SYMBOL(class_connect);

/* This function removes 1-3 references from the export:
 * 1 - for export pointer passed
 * and if disconnect really need
 * 2 - removing from hash
 * 3 - in client_unlink_export
 * The export pointer passed to this function can destroyed
 */
int class_disconnect(struct obd_export *export)
{
        int already_disconnected;

        if (!export) {
                CWARN("attempting to free NULL export %p\n", export);
                return -EINVAL;
        }

        spin_lock(&export->exp_lock);
        already_disconnected = export->exp_disconnected;
        export->exp_disconnected = 1;
        spin_unlock(&export->exp_lock);

        /* class_cleanup(), abort_recovery(), and class_fail_export()
         * all end up in here, and if any of them race we shouldn't
         * call extra class_export_puts().
         */
        if (already_disconnected)
                goto no_disconn;

        CDEBUG(D_IOCTL, "disconnect: cookie %#llx\n",
               export->exp_handle.h_cookie);

        class_unlink_export(export);
no_disconn:
        class_export_put(export);
        return 0;
}
EXPORT_SYMBOL(class_disconnect);

void class_fail_export(struct obd_export *exp)
{
        int rc, already_failed;

        spin_lock(&exp->exp_lock);
        already_failed = exp->exp_failed;
        exp->exp_failed = 1;
        spin_unlock(&exp->exp_lock);

        if (already_failed) {
                CDEBUG(D_HA, "disconnecting dead export %p/%s; skipping\n",
                       exp, exp->exp_client_uuid.uuid);
                return;
        }

        CDEBUG(D_HA, "disconnecting export %p/%s\n",
               exp, exp->exp_client_uuid.uuid);

        if (obd_dump_on_timeout)
                libcfs_debug_dumplog();

        /* need for safe call CDEBUG after obd_disconnect */
        class_export_get(exp);

        /* Most callers into obd_disconnect are removing their own reference
         * (request, for example) in addition to the one from the hash table.
         * We don't have such a reference here, so make one.
         */
        class_export_get(exp);
        rc = obd_disconnect(exp);
        if (rc)
                CERROR("disconnecting export %p failed: %d\n", exp, rc);
        else
                CDEBUG(D_HA, "disconnected export %p/%s\n",
                       exp, exp->exp_client_uuid.uuid);
        class_export_put(exp);
}
EXPORT_SYMBOL(class_fail_export);

#if LUSTRE_TRACKS_LOCK_EXP_REFS
void (*class_export_dump_hook)(struct obd_export *) = NULL;
EXPORT_SYMBOL(class_export_dump_hook);
#endif

/* Total amount of zombies to be destroyed */
static int zombies_count;

/**
 * kill zombie imports and exports
 */
static void obd_zombie_impexp_cull(void)
{
        struct obd_import *import;
        struct obd_export *export;

        do {
                spin_lock(&obd_zombie_impexp_lock);

                import = NULL;
                if (!list_empty(&obd_zombie_imports)) {
                        import = list_entry(obd_zombie_imports.next,
                                            struct obd_import,
                                            imp_zombie_chain);
                        list_del_init(&import->imp_zombie_chain);
                }

                export = NULL;
                if (!list_empty(&obd_zombie_exports)) {
                        export = list_entry(obd_zombie_exports.next,
                                            struct obd_export,
                                            exp_obd_chain);
                        list_del_init(&export->exp_obd_chain);
                }

                spin_unlock(&obd_zombie_impexp_lock);

                if (import) {
                        class_import_destroy(import);
                        spin_lock(&obd_zombie_impexp_lock);
                        zombies_count--;
                        spin_unlock(&obd_zombie_impexp_lock);
                }

                if (export) {
                        class_export_destroy(export);
                        spin_lock(&obd_zombie_impexp_lock);
                        zombies_count--;
                        spin_unlock(&obd_zombie_impexp_lock);
                }

                cond_resched();
        } while (import || export);
}

static struct completion        obd_zombie_start;
static struct completion        obd_zombie_stop;
static unsigned long            obd_zombie_flags;
static wait_queue_head_t                obd_zombie_waitq;
static pid_t                    obd_zombie_pid;

enum {
        OBD_ZOMBIE_STOP         = 0x0001,
};

/**
 * check for work for kill zombie import/export thread.
 */
static int obd_zombie_impexp_check(void *arg)
{
        int rc;

        spin_lock(&obd_zombie_impexp_lock);
        rc = (zombies_count == 0) &&
             !test_bit(OBD_ZOMBIE_STOP, &obd_zombie_flags);
        spin_unlock(&obd_zombie_impexp_lock);

        return rc;
}

/**
 * Add export to the obd_zombie thread and notify it.
 */
static void obd_zombie_export_add(struct obd_export *exp)
{
        spin_lock(&exp->exp_obd->obd_dev_lock);
        LASSERT(!list_empty(&exp->exp_obd_chain));
        list_del_init(&exp->exp_obd_chain);
        spin_unlock(&exp->exp_obd->obd_dev_lock);
        spin_lock(&obd_zombie_impexp_lock);
        zombies_count++;
        list_add(&exp->exp_obd_chain, &obd_zombie_exports);
        spin_unlock(&obd_zombie_impexp_lock);

        obd_zombie_impexp_notify();
}

/**
 * Add import to the obd_zombie thread and notify it.
 */
static void obd_zombie_import_add(struct obd_import *imp)
{
        LASSERT(!imp->imp_sec);
        spin_lock(&obd_zombie_impexp_lock);
        LASSERT(list_empty(&imp->imp_zombie_chain));
        zombies_count++;
        list_add(&imp->imp_zombie_chain, &obd_zombie_imports);
        spin_unlock(&obd_zombie_impexp_lock);

        obd_zombie_impexp_notify();
}

/**
 * notify import/export destroy thread about new zombie.
 */
static void obd_zombie_impexp_notify(void)
{
        /*
         * Make sure obd_zombie_impexp_thread get this notification.
         * It is possible this signal only get by obd_zombie_barrier, and
         * barrier gulps this notification and sleeps away and hangs ensues
         */
        wake_up_all(&obd_zombie_waitq);
}

/**
 * check whether obd_zombie is idle
 */
static int obd_zombie_is_idle(void)
{
        int rc;

        LASSERT(!test_bit(OBD_ZOMBIE_STOP, &obd_zombie_flags));
        spin_lock(&obd_zombie_impexp_lock);
        rc = (zombies_count == 0);
        spin_unlock(&obd_zombie_impexp_lock);
        return rc;
}

/**
 * wait when obd_zombie import/export queues become empty
 */
void obd_zombie_barrier(void)
{
        struct l_wait_info lwi = { 0 };

        if (obd_zombie_pid == current_pid())
                /* don't wait for myself */
                return;
        l_wait_event(obd_zombie_waitq, obd_zombie_is_idle(), &lwi);
}
EXPORT_SYMBOL(obd_zombie_barrier);

/**
 * destroy zombie export/import thread.
 */
static int obd_zombie_impexp_thread(void *unused)
{
        unshare_fs_struct();
        complete(&obd_zombie_start);

        obd_zombie_pid = current_pid();

        while (!test_bit(OBD_ZOMBIE_STOP, &obd_zombie_flags)) {
                struct l_wait_info lwi = { 0 };

                l_wait_event(obd_zombie_waitq,
                             !obd_zombie_impexp_check(NULL), &lwi);
                obd_zombie_impexp_cull();

                /*
                 * Notify obd_zombie_barrier callers that queues
                 * may be empty.
                 */
                wake_up(&obd_zombie_waitq);
        }

        complete(&obd_zombie_stop);

        return 0;
}

/**
 * start destroy zombie import/export thread
 */
int obd_zombie_impexp_init(void)
{
        struct task_struct *task;

        INIT_LIST_HEAD(&obd_zombie_imports);
        INIT_LIST_HEAD(&obd_zombie_exports);
        spin_lock_init(&obd_zombie_impexp_lock);
        init_completion(&obd_zombie_start);
        init_completion(&obd_zombie_stop);
        init_waitqueue_head(&obd_zombie_waitq);
        obd_zombie_pid = 0;

        task = kthread_run(obd_zombie_impexp_thread, NULL, "obd_zombid");
        if (IS_ERR(task))
                return PTR_ERR(task);

        wait_for_completion(&obd_zombie_start);
        return 0;
}

/**
 * stop destroy zombie import/export thread
 */
void obd_zombie_impexp_stop(void)
{
        set_bit(OBD_ZOMBIE_STOP, &obd_zombie_flags);
        obd_zombie_impexp_notify();
        wait_for_completion(&obd_zombie_stop);
}