/*
 * 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 COPYING file that accompanied this code.

 * 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
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2012, Intel Corporation.
 */
/*
 * lustre/obdclass/local_storage.c
 *
 * Local storage for file/objects with fid generation. Works on top of OSD.
 *
 * Author: Mikhail Pershin <mike.pershin@intel.com>
 */

#define DEBUG_SUBSYSTEM S_CLASS

#include "local_storage.h"

/* all initialized local storages on this node are linked on this */
static LIST_HEAD(ls_list_head);
static DEFINE_MUTEX(ls_list_mutex);

static int ls_object_init(const struct lu_env *env, struct lu_object *o,
                          const struct lu_object_conf *unused)
{
        struct ls_device        *ls;
        struct lu_object        *below;
        struct lu_device        *under;

        ls = container_of0(o->lo_dev, struct ls_device, ls_top_dev.dd_lu_dev);
        under = &ls->ls_osd->dd_lu_dev;
        below = under->ld_ops->ldo_object_alloc(env, o->lo_header, under);
        if (below == NULL)
                return -ENOMEM;

        lu_object_add(o, below);

        return 0;
}

static void ls_object_free(const struct lu_env *env, struct lu_object *o)
{
        struct ls_object        *obj = lu2ls_obj(o);
        struct lu_object_header *h = o->lo_header;

        dt_object_fini(&obj->ls_obj);
        lu_object_header_fini(h);
        OBD_FREE_PTR(obj);
}

struct lu_object_operations ls_lu_obj_ops = {
        .loo_object_init  = ls_object_init,
        .loo_object_free  = ls_object_free,
};

struct lu_object *ls_object_alloc(const struct lu_env *env,
                                  const struct lu_object_header *_h,
                                  struct lu_device *d)
{
        struct lu_object_header *h;
        struct ls_object        *o;
        struct lu_object        *l;

        LASSERT(_h == NULL);

        OBD_ALLOC_PTR(o);
        if (o != NULL) {
                l = &o->ls_obj.do_lu;
                h = &o->ls_header;

                lu_object_header_init(h);
                dt_object_init(&o->ls_obj, h, d);
                lu_object_add_top(h, l);

                l->lo_ops = &ls_lu_obj_ops;

                return l;
        } else {
                return NULL;
        }
}

static struct lu_device_operations ls_lu_dev_ops = {
        .ldo_object_alloc =     ls_object_alloc
};

static struct ls_device *__ls_find_dev(struct dt_device *dev)
{
        struct ls_device *ls, *ret = NULL;

        list_for_each_entry(ls, &ls_list_head, ls_linkage) {
                if (ls->ls_osd == dev) {
                        atomic_inc(&ls->ls_refcount);
                        ret = ls;
                        break;
                }
        }
        return ret;
}

struct ls_device *ls_find_dev(struct dt_device *dev)
{
        struct ls_device *ls;

        mutex_lock(&ls_list_mutex);
        ls = __ls_find_dev(dev);
        mutex_unlock(&ls_list_mutex);

        return ls;
}

static struct lu_device_type_operations ls_device_type_ops = {
        .ldto_start = NULL,
        .ldto_stop  = NULL,
};

static struct lu_device_type ls_lu_type = {
        .ldt_name = "local_storage",
        .ldt_ops  = &ls_device_type_ops,
};

struct ls_device *ls_device_get(struct dt_device *dev)
{
        struct ls_device *ls;

        mutex_lock(&ls_list_mutex);
        ls = __ls_find_dev(dev);
        if (ls)
                GOTO(out_ls, ls);

        /* not found, then create */
        OBD_ALLOC_PTR(ls);
        if (ls == NULL)
                GOTO(out_ls, ls = ERR_PTR(-ENOMEM));

        atomic_set(&ls->ls_refcount, 1);
        INIT_LIST_HEAD(&ls->ls_los_list);
        mutex_init(&ls->ls_los_mutex);

        ls->ls_osd = dev;

        LASSERT(dev->dd_lu_dev.ld_site);
        lu_device_init(&ls->ls_top_dev.dd_lu_dev, &ls_lu_type);
        ls->ls_top_dev.dd_lu_dev.ld_ops = &ls_lu_dev_ops;
        ls->ls_top_dev.dd_lu_dev.ld_site = dev->dd_lu_dev.ld_site;

        /* finally add ls to the list */
        list_add(&ls->ls_linkage, &ls_list_head);
out_ls:
        mutex_unlock(&ls_list_mutex);
        return ls;
}

void ls_device_put(const struct lu_env *env, struct ls_device *ls)
{
        LASSERT(env);
        if (!atomic_dec_and_test(&ls->ls_refcount))
                return;

        mutex_lock(&ls_list_mutex);
        if (atomic_read(&ls->ls_refcount) == 0) {
                LASSERT(list_empty(&ls->ls_los_list));
                list_del(&ls->ls_linkage);
                lu_site_purge(env, ls->ls_top_dev.dd_lu_dev.ld_site, ~0);
                lu_device_fini(&ls->ls_top_dev.dd_lu_dev);
                OBD_FREE_PTR(ls);
        }
        mutex_unlock(&ls_list_mutex);
}

/**
 * local file fid generation
 */
int local_object_fid_generate(const struct lu_env *env,
                              struct local_oid_storage *los,
                              struct lu_fid *fid)
{
        LASSERT(los->los_dev);
        LASSERT(los->los_obj);

        /* take next OID */

        /* to make it unique after reboot we store
         * the latest generated fid atomically with
         * object creation see local_object_create() */

        mutex_lock(&los->los_id_lock);
        fid->f_seq = los->los_seq;
        fid->f_oid = ++los->los_last_oid;
        fid->f_ver = 0;
        mutex_unlock(&los->los_id_lock);

        return 0;
}

int local_object_declare_create(const struct lu_env *env,
                                struct local_oid_storage *los,
                                struct dt_object *o, struct lu_attr *attr,
                                struct dt_object_format *dof,
                                struct thandle *th)
{
        struct dt_thread_info   *dti = dt_info(env);
        int                      rc;

        /* update fid generation file */
        if (los != NULL) {
                LASSERT(dt_object_exists(los->los_obj));
                rc = dt_declare_record_write(env, los->los_obj,
                                             sizeof(struct los_ondisk), 0, th);
                if (rc)
                        return rc;
        }

        rc = dt_declare_create(env, o, attr, NULL, dof, th);
        if (rc)
                return rc;

        dti->dti_lb.lb_buf = NULL;
        dti->dti_lb.lb_len = sizeof(dti->dti_lma);
        rc = dt_declare_xattr_set(env, o, &dti->dti_lb, XATTR_NAME_LMA, 0, th);

        return rc;
}

int local_object_create(const struct lu_env *env,
                        struct local_oid_storage *los,
                        struct dt_object *o, struct lu_attr *attr,
                        struct dt_object_format *dof, struct thandle *th)
{
        struct dt_thread_info   *dti = dt_info(env);
        obd_id                   lastid;
        int                      rc;

        rc = dt_create(env, o, attr, NULL, dof, th);
        if (rc)
                return rc;

        if (los == NULL)
                return rc;

        LASSERT(los->los_obj);
        LASSERT(dt_object_exists(los->los_obj));

        /* many threads can be updated this, serialize
         * them here to avoid the race where one thread
         * takes the value first, but writes it last */
        mutex_lock(&los->los_id_lock);

        /* update local oid number on disk so that
         * we know the last one used after reboot */
        lastid = cpu_to_le64(los->los_last_oid);

        dti->dti_off = 0;
        dti->dti_lb.lb_buf = &lastid;
        dti->dti_lb.lb_len = sizeof(lastid);
        rc = dt_record_write(env, los->los_obj, &dti->dti_lb, &dti->dti_off,
                             th);
        mutex_unlock(&los->los_id_lock);

        return rc;
}

/*
 * Create local named object (file, directory or index) in parent directory.
 */
struct dt_object *__local_file_create(const struct lu_env *env,
                                      const struct lu_fid *fid,
                                      struct local_oid_storage *los,
                                      struct ls_device *ls,
                                      struct dt_object *parent,
                                      const char *name, struct lu_attr *attr,
                                      struct dt_object_format *dof)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct dt_object        *dto;
        struct thandle          *th;
        int                      rc;

        dto = ls_locate(env, ls, fid);
        if (unlikely(IS_ERR(dto)))
                return dto;

        LASSERT(dto != NULL);
        if (dt_object_exists(dto))
                GOTO(out, rc = -EEXIST);

        th = dt_trans_create(env, ls->ls_osd);
        if (IS_ERR(th))
                GOTO(out, rc = PTR_ERR(th));

        rc = local_object_declare_create(env, los, dto, attr, dof, th);
        if (rc)
                GOTO(trans_stop, rc);

        if (dti->dti_dof.dof_type == DFT_DIR) {
                dt_declare_ref_add(env, dto, th);
                dt_declare_ref_add(env, parent, th);
        }

        rc = dt_declare_insert(env, parent, (void *)fid, (void *)name, th);
        if (rc)
                GOTO(trans_stop, rc);

        rc = dt_trans_start_local(env, ls->ls_osd, th);
        if (rc)
                GOTO(trans_stop, rc);

        dt_write_lock(env, dto, 0);
        if (dt_object_exists(dto))
                GOTO(unlock, rc = 0);

        CDEBUG(D_OTHER, "create new object "DFID"\n",
               PFID(lu_object_fid(&dto->do_lu)));
        rc = local_object_create(env, los, dto, attr, dof, th);
        if (rc)
                GOTO(unlock, rc);
        LASSERT(dt_object_exists(dto));

        if (dti->dti_dof.dof_type == DFT_DIR) {
                if (!dt_try_as_dir(env, dto))
                        GOTO(destroy, rc = -ENOTDIR);
                /* Add "." and ".." for newly created dir */
                rc = dt_insert(env, dto, (void *)fid, (void *)".", th,
                               BYPASS_CAPA, 1);
                if (rc)
                        GOTO(destroy, rc);
                dt_ref_add(env, dto, th);
                rc = dt_insert(env, dto, (void *)lu_object_fid(&parent->do_lu),
                               (void *)"..", th, BYPASS_CAPA, 1);
                if (rc)
                        GOTO(destroy, rc);
        }

        dt_write_lock(env, parent, 0);
        rc = dt_insert(env, parent, (const struct dt_rec *)fid,
                       (const struct dt_key *)name, th, BYPASS_CAPA, 1);
        if (dti->dti_dof.dof_type == DFT_DIR)
                dt_ref_add(env, parent, th);
        dt_write_unlock(env, parent);
        if (rc)
                GOTO(destroy, rc);
destroy:
        if (rc)
                dt_destroy(env, dto, th);
unlock:
        dt_write_unlock(env, dto);
trans_stop:
        dt_trans_stop(env, ls->ls_osd, th);
out:
        if (rc) {
                lu_object_put_nocache(env, &dto->do_lu);
                dto = ERR_PTR(rc);
        }
        return dto;
}

/*
 * Look up and create (if it does not exist) a local named file or directory in
 * parent directory.
 */
struct dt_object *local_file_find_or_create(const struct lu_env *env,
                                            struct local_oid_storage *los,
                                            struct dt_object *parent,
                                            const char *name, __u32 mode)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct dt_object        *dto;
        int                      rc;

        LASSERT(parent);

        rc = dt_lookup_dir(env, parent, name, &dti->dti_fid);
        if (rc == 0)
                /* name is found, get the object */
                dto = ls_locate(env, dt2ls_dev(los->los_dev), &dti->dti_fid);
        else if (rc != -ENOENT)
                dto = ERR_PTR(rc);
        else {
                rc = local_object_fid_generate(env, los, &dti->dti_fid);
                if (rc < 0) {
                        dto = ERR_PTR(rc);
                } else {
                        /* create the object */
                        dti->dti_attr.la_valid  = LA_MODE;
                        dti->dti_attr.la_mode   = mode;
                        dti->dti_dof.dof_type   = dt_mode_to_dft(mode & S_IFMT);
                        dto = __local_file_create(env, &dti->dti_fid, los,
                                                  dt2ls_dev(los->los_dev),
                                                  parent, name, &dti->dti_attr,
                                                  &dti->dti_dof);
                }
        }
        return dto;
}
EXPORT_SYMBOL(local_file_find_or_create);

struct dt_object *local_file_find_or_create_with_fid(const struct lu_env *env,
                                                     struct dt_device *dt,
                                                     const struct lu_fid *fid,
                                                     struct dt_object *parent,
                                                     const char *name,
                                                     __u32 mode)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct dt_object        *dto;
        int                      rc;

        LASSERT(parent);

        rc = dt_lookup_dir(env, parent, name, &dti->dti_fid);
        if (rc == 0) {
                dto = dt_locate(env, dt, &dti->dti_fid);
        } else if (rc != -ENOENT) {
                dto = ERR_PTR(rc);
        } else {
                struct ls_device *ls;

                ls = ls_device_get(dt);
                if (IS_ERR(ls)) {
                        dto = ERR_CAST(ls);
                } else {
                        /* create the object */
                        dti->dti_attr.la_valid  = LA_MODE;
                        dti->dti_attr.la_mode   = mode;
                        dti->dti_dof.dof_type   = dt_mode_to_dft(mode & S_IFMT);
                        dto = __local_file_create(env, fid, NULL, ls, parent,
                                                  name, &dti->dti_attr,
                                                  &dti->dti_dof);
                        /* ls_device_put() will finalize the ls device, we
                         * have to open the object in other device stack */
                        if (!IS_ERR(dto)) {
                                dti->dti_fid = dto->do_lu.lo_header->loh_fid;
                                lu_object_put_nocache(env, &dto->do_lu);
                                dto = dt_locate(env, dt, &dti->dti_fid);
                        }
                        ls_device_put(env, ls);
                }
        }
        return dto;
}
EXPORT_SYMBOL(local_file_find_or_create_with_fid);

/*
 * Look up and create (if it does not exist) a local named index file in parent
 * directory.
 */
struct dt_object *local_index_find_or_create(const struct lu_env *env,
                                             struct local_oid_storage *los,
                                             struct dt_object *parent,
                                             const char *name, __u32 mode,
                                             const struct dt_index_features *ft)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct dt_object        *dto;
        int                      rc;

        LASSERT(parent);

        rc = dt_lookup_dir(env, parent, name, &dti->dti_fid);
        if (rc == 0) {
                /* name is found, get the object */
                dto = ls_locate(env, dt2ls_dev(los->los_dev), &dti->dti_fid);
        } else if (rc != -ENOENT) {
                dto = ERR_PTR(rc);
        } else {
                rc = local_object_fid_generate(env, los, &dti->dti_fid);
                if (rc < 0) {
                        dto = ERR_PTR(rc);
                } else {
                        /* create the object */
                        dti->dti_attr.la_valid          = LA_MODE;
                        dti->dti_attr.la_mode           = mode;
                        dti->dti_dof.dof_type           = DFT_INDEX;
                        dti->dti_dof.u.dof_idx.di_feat  = ft;
                        dto = __local_file_create(env, &dti->dti_fid, los,
                                                  dt2ls_dev(los->los_dev),
                                                  parent, name, &dti->dti_attr,
                                                  &dti->dti_dof);
                }
        }
        return dto;

}
EXPORT_SYMBOL(local_index_find_or_create);

struct dt_object *
local_index_find_or_create_with_fid(const struct lu_env *env,
                                    struct dt_device *dt,
                                    const struct lu_fid *fid,
                                    struct dt_object *parent,
                                    const char *name, __u32 mode,
                                    const struct dt_index_features *ft)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct dt_object        *dto;
        int                      rc;

        LASSERT(parent);

        rc = dt_lookup_dir(env, parent, name, &dti->dti_fid);
        if (rc == 0) {
                /* name is found, get the object */
                if (!lu_fid_eq(fid, &dti->dti_fid))
                        dto = ERR_PTR(-EINVAL);
                else
                        dto = dt_locate(env, dt, fid);
        } else if (rc != -ENOENT) {
                dto = ERR_PTR(rc);
        } else {
                struct ls_device *ls;

                ls = ls_device_get(dt);
                if (IS_ERR(ls)) {
                        dto = ERR_CAST(ls);
                } else {
                        /* create the object */
                        dti->dti_attr.la_valid          = LA_MODE;
                        dti->dti_attr.la_mode           = mode;
                        dti->dti_dof.dof_type           = DFT_INDEX;
                        dti->dti_dof.u.dof_idx.di_feat  = ft;
                        dto = __local_file_create(env, fid, NULL, ls, parent,
                                                  name, &dti->dti_attr,
                                                  &dti->dti_dof);
                        /* ls_device_put() will finalize the ls device, we
                         * have to open the object in other device stack */
                        if (!IS_ERR(dto)) {
                                dti->dti_fid = dto->do_lu.lo_header->loh_fid;
                                lu_object_put_nocache(env, &dto->do_lu);
                                dto = dt_locate(env, dt, &dti->dti_fid);
                        }
                        ls_device_put(env, ls);
                }
        }
        return dto;
}
EXPORT_SYMBOL(local_index_find_or_create_with_fid);

static int local_object_declare_unlink(const struct lu_env *env,
                                       struct dt_device *dt,
                                       struct dt_object *p,
                                       struct dt_object *c, const char *name,
                                       struct thandle *th)
{
        int rc;

        rc = dt_declare_delete(env, p, (const struct dt_key *)name, th);
        if (rc < 0)
                return rc;

        rc = dt_declare_ref_del(env, c, th);
        if (rc < 0)
                return rc;

        return dt_declare_destroy(env, c, th);
}

int local_object_unlink(const struct lu_env *env, struct dt_device *dt,
                        struct dt_object *parent, const char *name)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct dt_object        *dto;
        struct thandle          *th;
        int                      rc;

        rc = dt_lookup_dir(env, parent, name, &dti->dti_fid);
        if (rc == -ENOENT)
                return 0;
        else if (rc < 0)
                return rc;

        dto = dt_locate(env, dt, &dti->dti_fid);
        if (unlikely(IS_ERR(dto)))
                return PTR_ERR(dto);

        th = dt_trans_create(env, dt);
        if (IS_ERR(th))
                GOTO(out, rc = PTR_ERR(th));

        rc = local_object_declare_unlink(env, dt, parent, dto, name, th);
        if (rc < 0)
                GOTO(stop, rc);

        rc = dt_trans_start_local(env, dt, th);
        if (rc < 0)
                GOTO(stop, rc);

        dt_write_lock(env, dto, 0);
        rc = dt_delete(env, parent, (struct dt_key *)name, th, BYPASS_CAPA);
        if (rc < 0)
                GOTO(unlock, rc);

        rc = dt_ref_del(env, dto, th);
        if (rc < 0) {
                rc = dt_insert(env, parent,
                               (const struct dt_rec *)&dti->dti_fid,
                               (const struct dt_key *)name, th, BYPASS_CAPA, 1);
                GOTO(unlock, rc);
        }

        rc = dt_destroy(env, dto, th);
unlock:
        dt_write_unlock(env, dto);
stop:
        dt_trans_stop(env, dt, th);
out:
        lu_object_put_nocache(env, &dto->do_lu);
        return rc;
}
EXPORT_SYMBOL(local_object_unlink);

struct local_oid_storage *dt_los_find(struct ls_device *ls, __u64 seq)
{
        struct local_oid_storage *los, *ret = NULL;

        list_for_each_entry(los, &ls->ls_los_list, los_list) {
                if (los->los_seq == seq) {
                        atomic_inc(&los->los_refcount);
                        ret = los;
                        break;
                }
        }
        return ret;
}

void dt_los_put(struct local_oid_storage *los)
{
        if (atomic_dec_and_test(&los->los_refcount))
                /* should never happen, only local_oid_storage_fini should
                 * drop refcount to zero */
                LBUG();
        return;
}

/* after Lustre 2.3 release there may be old file to store last generated FID
 * If such file exists then we have to read its content
 */
int lastid_compat_check(const struct lu_env *env, struct dt_device *dev,
                        __u64 lastid_seq, __u32 *first_oid, struct ls_device *ls)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct dt_object        *root = NULL;
        struct los_ondisk        losd;
        struct dt_object        *o = NULL;
        int                      rc = 0;

        rc = dt_root_get(env, dev, &dti->dti_fid);
        if (rc)
                return rc;

        root = ls_locate(env, ls, &dti->dti_fid);
        if (IS_ERR(root))
                return PTR_ERR(root);

        /* find old last_id file */
        snprintf(dti->dti_buf, sizeof(dti->dti_buf), "seq-"LPX64"-lastid",
                 lastid_seq);
        rc = dt_lookup_dir(env, root, dti->dti_buf, &dti->dti_fid);
        lu_object_put_nocache(env, &root->do_lu);
        if (rc == -ENOENT) {
                /* old llog lastid accessed by FID only */
                if (lastid_seq != FID_SEQ_LLOG)
                        return 0;
                dti->dti_fid.f_seq = FID_SEQ_LLOG;
                dti->dti_fid.f_oid = 1;
                dti->dti_fid.f_ver = 0;
                o = ls_locate(env, ls, &dti->dti_fid);
                if (IS_ERR(o))
                        return PTR_ERR(o);

                if (!dt_object_exists(o)) {
                        lu_object_put_nocache(env, &o->do_lu);
                        return 0;
                }
                CDEBUG(D_INFO, "Found old llog lastid file\n");
        } else if (rc < 0) {
                return rc;
        } else {
                CDEBUG(D_INFO, "Found old lastid file for sequence "LPX64"\n",
                       lastid_seq);
                o = ls_locate(env, ls, &dti->dti_fid);
                if (IS_ERR(o))
                        return PTR_ERR(o);
        }
        /* let's read seq-NNNNNN-lastid file value */
        LASSERT(dt_object_exists(o));
        dti->dti_off = 0;
        dti->dti_lb.lb_buf = &losd;
        dti->dti_lb.lb_len = sizeof(losd);
        dt_read_lock(env, o, 0);
        rc = dt_record_read(env, o, &dti->dti_lb, &dti->dti_off);
        dt_read_unlock(env, o);
        lu_object_put_nocache(env, &o->do_lu);
        if (rc == 0 && le32_to_cpu(losd.lso_magic) != LOS_MAGIC) {
                CERROR("%s: wrong content of seq-"LPX64"-lastid file, magic %x\n",
                       o->do_lu.lo_dev->ld_obd->obd_name, lastid_seq,
                       le32_to_cpu(losd.lso_magic));
                return -EINVAL;
        } else if (rc < 0) {
                CERROR("%s: failed to read seq-"LPX64"-lastid: rc = %d\n",
                       o->do_lu.lo_dev->ld_obd->obd_name, lastid_seq, rc);
                return rc;
        }
        *first_oid = le32_to_cpu(losd.lso_next_oid);
        return rc;
}

/**
 * Initialize local OID storage for required sequence.
 * That may be needed for services that uses local files and requires
 * dynamic OID allocation for them.
 *
 * Per each sequence we have an object with 'first_fid' identificator
 * containing the counter for OIDs of locally created files with that
 * sequence.
 *
 * It is used now by llog subsystem and MGS for NID tables
 *
 * Function gets first_fid to create counter object.
 * All dynamic fids will be generated with the same sequence and incremented
 * OIDs
 *
 * Returned local_oid_storage is in-memory representaion of OID storage
 */
int local_oid_storage_init(const struct lu_env *env, struct dt_device *dev,
                           const struct lu_fid *first_fid,
                           struct local_oid_storage **los)
{
        struct dt_thread_info   *dti = dt_info(env);
        struct ls_device        *ls;
        obd_id                   lastid;
        struct dt_object        *o = NULL;
        struct thandle          *th;
        __u32                    first_oid = fid_oid(first_fid);
        int                      rc = 0;

        ls = ls_device_get(dev);
        if (IS_ERR(ls))
                return PTR_ERR(ls);

        mutex_lock(&ls->ls_los_mutex);
        *los = dt_los_find(ls, fid_seq(first_fid));
        if (*los != NULL)
                GOTO(out, rc = 0);

        /* not found, then create */
        OBD_ALLOC_PTR(*los);
        if (*los == NULL)
                GOTO(out, rc = -ENOMEM);

        atomic_set(&(*los)->los_refcount, 1);
        mutex_init(&(*los)->los_id_lock);
        (*los)->los_dev = &ls->ls_top_dev;
        atomic_inc(&ls->ls_refcount);
        list_add(&(*los)->los_list, &ls->ls_los_list);

        /* Use {seq, 0, 0} to create the LAST_ID file for every
         * sequence.  OIDs start at LUSTRE_FID_INIT_OID.
         */
        dti->dti_fid.f_seq = fid_seq(first_fid);
        dti->dti_fid.f_oid = LUSTRE_FID_LASTID_OID;
        dti->dti_fid.f_ver = 0;
        o = ls_locate(env, ls, &dti->dti_fid);
        if (IS_ERR(o))
                GOTO(out_los, rc = PTR_ERR(o));

        if (!dt_object_exists(o)) {
                rc = lastid_compat_check(env, dev, fid_seq(first_fid),
                                         &first_oid, ls);
                if (rc < 0)
                        GOTO(out_los, rc);

                th = dt_trans_create(env, dev);
                if (IS_ERR(th))
                        GOTO(out_los, rc = PTR_ERR(th));

                dti->dti_attr.la_valid = LA_MODE | LA_TYPE;
                dti->dti_attr.la_mode = S_IFREG | S_IRUGO | S_IWUSR;
                dti->dti_dof.dof_type = dt_mode_to_dft(S_IFREG);

                rc = dt_declare_create(env, o, &dti->dti_attr, NULL,
                                       &dti->dti_dof, th);
                if (rc)
                        GOTO(out_trans, rc);

                rc = dt_declare_record_write(env, o, sizeof(lastid), 0, th);
                if (rc)
                        GOTO(out_trans, rc);

                rc = dt_trans_start_local(env, dev, th);
                if (rc)
                        GOTO(out_trans, rc);

                dt_write_lock(env, o, 0);
                if (dt_object_exists(o))
                        GOTO(out_lock, rc = 0);

                rc = dt_create(env, o, &dti->dti_attr, NULL, &dti->dti_dof,
                               th);
                if (rc)
                        GOTO(out_lock, rc);

                lastid = cpu_to_le64(first_oid);

                dti->dti_off = 0;
                dti->dti_lb.lb_buf = &lastid;
                dti->dti_lb.lb_len = sizeof(lastid);
                rc = dt_record_write(env, o, &dti->dti_lb, &dti->dti_off, th);
                if (rc)
                        GOTO(out_lock, rc);
out_lock:
                dt_write_unlock(env, o);
out_trans:
                dt_trans_stop(env, dev, th);
        } else {
                dti->dti_off = 0;
                dti->dti_lb.lb_buf = &lastid;
                dti->dti_lb.lb_len = sizeof(lastid);
                dt_read_lock(env, o, 0);
                rc = dt_record_read(env, o, &dti->dti_lb, &dti->dti_off);
                dt_read_unlock(env, o);
                if (rc == 0 && le64_to_cpu(lastid) > OBIF_MAX_OID) {
                        CERROR("%s: bad oid "LPU64" is read from LAST_ID\n",
                               o->do_lu.lo_dev->ld_obd->obd_name,
                               le64_to_cpu(lastid));
                        rc = -EINVAL;
                }
        }
out_los:
        if (rc != 0) {
                list_del(&(*los)->los_list);
                atomic_dec(&ls->ls_refcount);
                OBD_FREE_PTR(*los);
                *los = NULL;
                if (o != NULL && !IS_ERR(o))
                        lu_object_put_nocache(env, &o->do_lu);
        } else {
                (*los)->los_seq = fid_seq(first_fid);
                (*los)->los_last_oid = le64_to_cpu(lastid);
                (*los)->los_obj = o;
                /* read value should not be less than initial one */
                LASSERTF((*los)->los_last_oid >= first_oid, "%u < %u\n",
                         (*los)->los_last_oid, first_oid);
        }
out:
        mutex_unlock(&ls->ls_los_mutex);
        ls_device_put(env, ls);
        return rc;
}
EXPORT_SYMBOL(local_oid_storage_init);

void local_oid_storage_fini(const struct lu_env *env,
                            struct local_oid_storage *los)
{
        struct ls_device *ls;

        if (!atomic_dec_and_test(&los->los_refcount))
                return;

        LASSERT(env);
        LASSERT(los->los_dev);
        ls = dt2ls_dev(los->los_dev);

        mutex_lock(&ls->ls_los_mutex);
        if (atomic_read(&los->los_refcount) == 0) {
                if (los->los_obj)
                        lu_object_put_nocache(env, &los->los_obj->do_lu);
                list_del(&los->los_list);
                OBD_FREE_PTR(los);
        }
        mutex_unlock(&ls->ls_los_mutex);
        ls_device_put(env, ls);
}
EXPORT_SYMBOL(local_oid_storage_fini);