/*
 * 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.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/obdclass/dt_object.c
 *
 * Dt Object.
 * Generic functions from dt_object.h
 *
 * Author: Nikita Danilov <nikita@clusterfs.com>
 */

#define DEBUG_SUBSYSTEM S_CLASS

#include <obd.h>
#include <dt_object.h>
#include <linux/list.h>
/* fid_be_to_cpu() */
#include <lustre_fid.h>

#include <lustre_quota.h>

/* context key constructor/destructor: dt_global_key_init, dt_global_key_fini */
LU_KEY_INIT(dt_global, struct dt_thread_info);
LU_KEY_FINI(dt_global, struct dt_thread_info);

struct lu_context_key dt_key = {
        .lct_tags = LCT_MD_THREAD | LCT_DT_THREAD | LCT_MG_THREAD | LCT_LOCAL,
        .lct_init = dt_global_key_init,
        .lct_fini = dt_global_key_fini
};
EXPORT_SYMBOL(dt_key);

/* no lock is necessary to protect the list, because call-backs
 * are added during system startup. Please refer to "struct dt_device".
 */
void dt_txn_callback_add(struct dt_device *dev, struct dt_txn_callback *cb)
{
        list_add(&cb->dtc_linkage, &dev->dd_txn_callbacks);
}
EXPORT_SYMBOL(dt_txn_callback_add);

void dt_txn_callback_del(struct dt_device *dev, struct dt_txn_callback *cb)
{
        list_del_init(&cb->dtc_linkage);
}
EXPORT_SYMBOL(dt_txn_callback_del);

int dt_txn_hook_start(const struct lu_env *env,
                      struct dt_device *dev, struct thandle *th)
{
        int rc = 0;
        struct dt_txn_callback *cb;

        if (th->th_local)
                return 0;

        list_for_each_entry(cb, &dev->dd_txn_callbacks, dtc_linkage) {
                if (cb->dtc_txn_start == NULL ||
                    !(cb->dtc_tag & env->le_ctx.lc_tags))
                        continue;
                rc = cb->dtc_txn_start(env, th, cb->dtc_cookie);
                if (rc < 0)
                        break;
        }
        return rc;
}
EXPORT_SYMBOL(dt_txn_hook_start);

int dt_txn_hook_stop(const struct lu_env *env, struct thandle *txn)
{
        struct dt_device       *dev = txn->th_dev;
        struct dt_txn_callback *cb;
        int                  rc = 0;

        if (txn->th_local)
                return 0;

        list_for_each_entry(cb, &dev->dd_txn_callbacks, dtc_linkage) {
                if (cb->dtc_txn_stop == NULL ||
                    !(cb->dtc_tag & env->le_ctx.lc_tags))
                        continue;
                rc = cb->dtc_txn_stop(env, txn, cb->dtc_cookie);
                if (rc < 0)
                        break;
        }
        return rc;
}
EXPORT_SYMBOL(dt_txn_hook_stop);

void dt_txn_hook_commit(struct thandle *txn)
{
        struct dt_txn_callback *cb;

        if (txn->th_local)
                return;

        list_for_each_entry(cb, &txn->th_dev->dd_txn_callbacks,
                                dtc_linkage) {
                if (cb->dtc_txn_commit)
                        cb->dtc_txn_commit(txn, cb->dtc_cookie);
        }
}
EXPORT_SYMBOL(dt_txn_hook_commit);

int dt_device_init(struct dt_device *dev, struct lu_device_type *t)
{

        INIT_LIST_HEAD(&dev->dd_txn_callbacks);
        return lu_device_init(&dev->dd_lu_dev, t);
}
EXPORT_SYMBOL(dt_device_init);

void dt_device_fini(struct dt_device *dev)
{
        lu_device_fini(&dev->dd_lu_dev);
}
EXPORT_SYMBOL(dt_device_fini);

int dt_object_init(struct dt_object *obj,
                   struct lu_object_header *h, struct lu_device *d)

{
        return lu_object_init(&obj->do_lu, h, d);
}
EXPORT_SYMBOL(dt_object_init);

void dt_object_fini(struct dt_object *obj)
{
        lu_object_fini(&obj->do_lu);
}
EXPORT_SYMBOL(dt_object_fini);

int dt_try_as_dir(const struct lu_env *env, struct dt_object *obj)
{
        if (obj->do_index_ops == NULL)
                obj->do_ops->do_index_try(env, obj, &dt_directory_features);
        return obj->do_index_ops != NULL;
}
EXPORT_SYMBOL(dt_try_as_dir);

enum dt_format_type dt_mode_to_dft(__u32 mode)
{
        enum dt_format_type result;

        switch (mode & S_IFMT) {
        case S_IFDIR:
                result = DFT_DIR;
                break;
        case S_IFREG:
                result = DFT_REGULAR;
                break;
        case S_IFLNK:
                result = DFT_SYM;
                break;
        case S_IFCHR:
        case S_IFBLK:
        case S_IFIFO:
        case S_IFSOCK:
                result = DFT_NODE;
                break;
        default:
                LBUG();
                break;
        }
        return result;
}
EXPORT_SYMBOL(dt_mode_to_dft);

/**
 * lookup fid for object named \a name in directory \a dir.
 */

int dt_lookup_dir(const struct lu_env *env, struct dt_object *dir,
                  const char *name, struct lu_fid *fid)
{
        if (dt_try_as_dir(env, dir))
                return dt_lookup(env, dir, (struct dt_rec *)fid,
                                 (const struct dt_key *)name, BYPASS_CAPA);
        return -ENOTDIR;
}
EXPORT_SYMBOL(dt_lookup_dir);

/* this differs from dt_locate by top_dev as parameter
 * but not one from lu_site */
struct dt_object *dt_locate_at(const struct lu_env *env,
                               struct dt_device *dev, const struct lu_fid *fid,
                               struct lu_device *top_dev)
{
        struct lu_object *lo, *n;
        ENTRY;

        lo = lu_object_find_at(env, top_dev, fid, NULL);
        if (IS_ERR(lo))
                return (void *)lo;

        LASSERT(lo != NULL);

        list_for_each_entry(n, &lo->lo_header->loh_layers, lo_linkage) {
                if (n->lo_dev == &dev->dd_lu_dev)
                        return container_of0(n, struct dt_object, do_lu);
        }
        return ERR_PTR(-ENOENT);
}
EXPORT_SYMBOL(dt_locate_at);

/**
 * find a object named \a entry in given \a dfh->dfh_o directory.
 */
static int dt_find_entry(const struct lu_env *env, const char *entry, void *data)
{
        struct dt_find_hint  *dfh = data;
        struct dt_device     *dt = dfh->dfh_dt;
        struct lu_fid   *fid = dfh->dfh_fid;
        struct dt_object     *obj = dfh->dfh_o;
        int                result;

        result = dt_lookup_dir(env, obj, entry, fid);
        lu_object_put(env, &obj->do_lu);
        if (result == 0) {
                obj = dt_locate(env, dt, fid);
                if (IS_ERR(obj))
                        result = PTR_ERR(obj);
        }
        dfh->dfh_o = obj;
        return result;
}

/**
 * Abstract function which parses path name. This function feeds
 * path component to \a entry_func.
 */
int dt_path_parser(const struct lu_env *env,
                   char *path, dt_entry_func_t entry_func,
                   void *data)
{
        char *e;
        int rc = 0;

        while (1) {
                e = strsep(&path, "/");
                if (e == NULL)
                        break;

                if (e[0] == 0) {
                        if (!path || path[0] == '\0')
                                break;
                        continue;
                }
                rc = entry_func(env, e, data);
                if (rc)
                        break;
        }

        return rc;
}

struct dt_object *
dt_store_resolve(const struct lu_env *env, struct dt_device *dt,
                 const char *path, struct lu_fid *fid)
{
        struct dt_thread_info *info = dt_info(env);
        struct dt_find_hint   *dfh = &info->dti_dfh;
        struct dt_object      *obj;
        char                  *local = info->dti_buf;
        int                    result;


        dfh->dfh_dt = dt;
        dfh->dfh_fid = fid;

        strncpy(local, path, DT_MAX_PATH);
        local[DT_MAX_PATH - 1] = '\0';

        result = dt->dd_ops->dt_root_get(env, dt, fid);
        if (result == 0) {
                obj = dt_locate(env, dt, fid);
                if (!IS_ERR(obj)) {
                        dfh->dfh_o = obj;
                        result = dt_path_parser(env, local, dt_find_entry, dfh);
                        if (result != 0)
                                obj = ERR_PTR(result);
                        else
                                obj = dfh->dfh_o;
                }
        } else {
                obj = ERR_PTR(result);
        }
        return obj;
}
EXPORT_SYMBOL(dt_store_resolve);

static struct dt_object *dt_reg_open(const struct lu_env *env,
                                     struct dt_device *dt,
                                     struct dt_object *p,
                                     const char *name,
                                     struct lu_fid *fid)
{
        struct dt_object *o;
        int result;

        result = dt_lookup_dir(env, p, name, fid);
        if (result == 0){
                o = dt_locate(env, dt, fid);
        }
        else
                o = ERR_PTR(result);

        return o;
}

/**
 * Open dt object named \a filename from \a dirname directory.
 *      \param  dt      dt device
 *      \param  fid     on success, object fid is stored in *fid
 */
struct dt_object *dt_store_open(const struct lu_env *env,
                                struct dt_device *dt,
                                const char *dirname,
                                const char *filename,
                                struct lu_fid *fid)
{
        struct dt_object *file;
        struct dt_object *dir;

        dir = dt_store_resolve(env, dt, dirname, fid);
        if (!IS_ERR(dir)) {
                file = dt_reg_open(env, dt, dir,
                                   filename, fid);
                lu_object_put(env, &dir->do_lu);
        } else {
                file = dir;
        }
        return file;
}
EXPORT_SYMBOL(dt_store_open);

struct dt_object *dt_find_or_create(const struct lu_env *env,
                                    struct dt_device *dt,
                                    const struct lu_fid *fid,
                                    struct dt_object_format *dof,
                                    struct lu_attr *at)
{
        struct dt_object *dto;
        struct thandle *th;
        int rc;

        ENTRY;

        dto = dt_locate(env, dt, fid);
        if (IS_ERR(dto))
                RETURN(dto);

        LASSERT(dto != NULL);
        if (dt_object_exists(dto))
                RETURN(dto);

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

        rc = dt_declare_create(env, dto, at, NULL, dof, th);
        if (rc)
                GOTO(trans_stop, rc);

        rc = dt_trans_start_local(env, dt, 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(fid));

        rc = dt_create(env, dto, at, NULL, dof, th);
        if (rc)
                GOTO(unlock, rc);
        LASSERT(dt_object_exists(dto));
unlock:
        dt_write_unlock(env, dto);
trans_stop:
        dt_trans_stop(env, dt, th);
out:
        if (rc) {
                lu_object_put(env, &dto->do_lu);
                RETURN(ERR_PTR(rc));
        }
        RETURN(dto);
}
EXPORT_SYMBOL(dt_find_or_create);

/* dt class init function. */
int dt_global_init(void)
{
        int result;

        LU_CONTEXT_KEY_INIT(&dt_key);
        result = lu_context_key_register(&dt_key);
        return result;
}

void dt_global_fini(void)
{
        lu_context_key_degister(&dt_key);
}

/**
 * Generic read helper. May return an error for partial reads.
 *
 * \param env  lustre environment
 * \param dt   object to be read
 * \param buf  lu_buf to be filled, with buffer pointer and length
 * \param pos position to start reading, updated as data is read
 *
 * \retval real size of data read
 * \retval -ve errno on failure
 */
int dt_read(const struct lu_env *env, struct dt_object *dt,
            struct lu_buf *buf, loff_t *pos)
{
        LASSERTF(dt != NULL, "dt is NULL when we want to read record\n");
        return dt->do_body_ops->dbo_read(env, dt, buf, pos, BYPASS_CAPA);
}
EXPORT_SYMBOL(dt_read);

/**
 * Read structures of fixed size from storage.  Unlike dt_read(), using
 * dt_record_read() will return an error for partial reads.
 *
 * \param env  lustre environment
 * \param dt   object to be read
 * \param buf  lu_buf to be filled, with buffer pointer and length
 * \param pos position to start reading, updated as data is read
 *
 * \retval 0 on successfully reading full buffer
 * \retval -EFAULT on short read
 * \retval -ve errno on failure
 */
int dt_record_read(const struct lu_env *env, struct dt_object *dt,
                   struct lu_buf *buf, loff_t *pos)
{
        int rc;

        LASSERTF(dt != NULL, "dt is NULL when we want to read record\n");

        rc = dt->do_body_ops->dbo_read(env, dt, buf, pos, BYPASS_CAPA);

        if (rc == buf->lb_len)
                rc = 0;
        else if (rc >= 0)
                rc = -EFAULT;
        return rc;
}
EXPORT_SYMBOL(dt_record_read);

int dt_record_write(const struct lu_env *env, struct dt_object *dt,
                    const struct lu_buf *buf, loff_t *pos, struct thandle *th)
{
        int rc;

        LASSERTF(dt != NULL, "dt is NULL when we want to write record\n");
        LASSERT(th != NULL);
        LASSERT(dt->do_body_ops);
        LASSERT(dt->do_body_ops->dbo_write);
        rc = dt->do_body_ops->dbo_write(env, dt, buf, pos, th, BYPASS_CAPA, 1);
        if (rc == buf->lb_len)
                rc = 0;
        else if (rc >= 0)
                rc = -EFAULT;
        return rc;
}
EXPORT_SYMBOL(dt_record_write);

int dt_declare_version_set(const struct lu_env *env, struct dt_object *o,
                           struct thandle *th)
{
        struct lu_buf vbuf;
        char *xname = XATTR_NAME_VERSION;

        LASSERT(o);
        vbuf.lb_buf = NULL;
        vbuf.lb_len = sizeof(dt_obj_version_t);
        return dt_declare_xattr_set(env, o, &vbuf, xname, 0, th);

}
EXPORT_SYMBOL(dt_declare_version_set);

void dt_version_set(const struct lu_env *env, struct dt_object *o,
                    dt_obj_version_t version, struct thandle *th)
{
        struct lu_buf vbuf;
        char *xname = XATTR_NAME_VERSION;
        int rc;

        LASSERT(o);
        vbuf.lb_buf = &version;
        vbuf.lb_len = sizeof(version);

        rc = dt_xattr_set(env, o, &vbuf, xname, 0, th, BYPASS_CAPA);
        if (rc < 0)
                CDEBUG(D_INODE, "Can't set version, rc %d\n", rc);
        return;
}
EXPORT_SYMBOL(dt_version_set);

dt_obj_version_t dt_version_get(const struct lu_env *env, struct dt_object *o)
{
        struct lu_buf vbuf;
        char *xname = XATTR_NAME_VERSION;
        dt_obj_version_t version;
        int rc;

        LASSERT(o);
        vbuf.lb_buf = &version;
        vbuf.lb_len = sizeof(version);
        rc = dt_xattr_get(env, o, &vbuf, xname, BYPASS_CAPA);
        if (rc != sizeof(version)) {
                CDEBUG(D_INODE, "Can't get version, rc %d\n", rc);
                version = 0;
        }
        return version;
}
EXPORT_SYMBOL(dt_version_get);

/* list of all supported index types */

/* directories */
const struct dt_index_features dt_directory_features;
EXPORT_SYMBOL(dt_directory_features);

/* scrub iterator */
const struct dt_index_features dt_otable_features;
EXPORT_SYMBOL(dt_otable_features);

/* lfsck */
const struct dt_index_features dt_lfsck_features = {
        .dif_flags              = DT_IND_UPDATE,
        .dif_keysize_min        = sizeof(struct lu_fid),
        .dif_keysize_max        = sizeof(struct lu_fid),
        .dif_recsize_min        = sizeof(__u8),
        .dif_recsize_max        = sizeof(__u8),
        .dif_ptrsize            = 4
};
EXPORT_SYMBOL(dt_lfsck_features);

/* accounting indexes */
const struct dt_index_features dt_acct_features = {
        .dif_flags              = DT_IND_UPDATE,
        .dif_keysize_min        = sizeof(__u64), /* 64-bit uid/gid */
        .dif_keysize_max        = sizeof(__u64), /* 64-bit uid/gid */
        .dif_recsize_min        = sizeof(struct lquota_acct_rec), /* 16 bytes */
        .dif_recsize_max        = sizeof(struct lquota_acct_rec), /* 16 bytes */
        .dif_ptrsize            = 4
};
EXPORT_SYMBOL(dt_acct_features);

/* global quota files */
const struct dt_index_features dt_quota_glb_features = {
        .dif_flags              = DT_IND_UPDATE,
        /* a different key would have to be used for per-directory quota */
        .dif_keysize_min        = sizeof(__u64), /* 64-bit uid/gid */
        .dif_keysize_max        = sizeof(__u64), /* 64-bit uid/gid */
        .dif_recsize_min        = sizeof(struct lquota_glb_rec), /* 32 bytes */
        .dif_recsize_max        = sizeof(struct lquota_glb_rec), /* 32 bytes */
        .dif_ptrsize            = 4
};
EXPORT_SYMBOL(dt_quota_glb_features);

/* slave quota files */
const struct dt_index_features dt_quota_slv_features = {
        .dif_flags              = DT_IND_UPDATE,
        /* a different key would have to be used for per-directory quota */
        .dif_keysize_min        = sizeof(__u64), /* 64-bit uid/gid */
        .dif_keysize_max        = sizeof(__u64), /* 64-bit uid/gid */
        .dif_recsize_min        = sizeof(struct lquota_slv_rec), /* 8 bytes */
        .dif_recsize_max        = sizeof(struct lquota_slv_rec), /* 8 bytes */
        .dif_ptrsize            = 4
};
EXPORT_SYMBOL(dt_quota_slv_features);

/* helper function returning what dt_index_features structure should be used
 * based on the FID sequence. This is used by OBD_IDX_READ RPC */
static inline const struct dt_index_features *dt_index_feat_select(__u64 seq,
                                                                   __u32 mode)
{
        if (seq == FID_SEQ_QUOTA_GLB) {
                /* global quota index */
                if (!S_ISREG(mode))
                        /* global quota index should be a regular file */
                        return ERR_PTR(-ENOENT);
                return &dt_quota_glb_features;
        } else if (seq == FID_SEQ_QUOTA) {
                /* quota slave index */
                if (!S_ISREG(mode))
                        /* slave index should be a regular file */
                        return ERR_PTR(-ENOENT);
                return &dt_quota_slv_features;
        } else if (seq >= FID_SEQ_NORMAL) {
                /* object is part of the namespace, verify that it is a
                 * directory */
                if (!S_ISDIR(mode))
                        /* sorry, we can only deal with directory */
                        return ERR_PTR(-ENOTDIR);
                return &dt_directory_features;
        }

        return ERR_PTR(-EOPNOTSUPP);
}

/*
 * Fill a lu_idxpage with key/record pairs read for transfer via OBD_IDX_READ
 * RPC
 *
 * \param env - is the environment passed by the caller
 * \param lp  - is a pointer to the lu_page to fill
 * \param nob - is the maximum number of bytes that should be copied
 * \param iops - is the index operation vector associated with the index object
 * \param it   - is a pointer to the current iterator
 * \param attr - is the index attribute to pass to iops->rec()
 * \param arg  - is a pointer to the idx_info structure
 */
static int dt_index_page_build(const struct lu_env *env, union lu_page *lp,
                               int nob, const struct dt_it_ops *iops,
                               struct dt_it *it, __u32 attr, void *arg)
{
        struct idx_info         *ii = (struct idx_info *)arg;
        struct lu_idxpage       *lip = &lp->lp_idx;
        char                    *entry;
        int                      rc, size;
        ENTRY;

        /* no support for variable key & record size for now */
        LASSERT((ii->ii_flags & II_FL_VARKEY) == 0);
        LASSERT((ii->ii_flags & II_FL_VARREC) == 0);

        /* initialize the header of the new container */
        memset(lip, 0, LIP_HDR_SIZE);
        lip->lip_magic = LIP_MAGIC;
        nob        -= LIP_HDR_SIZE;

        /* compute size needed to store a key/record pair */
        size = ii->ii_recsize + ii->ii_keysize;
        if ((ii->ii_flags & II_FL_NOHASH) == 0)
                /* add hash if the client wants it */
                size += sizeof(__u64);

        entry = lip->lip_entries;
        do {
                char            *tmp_entry = entry;
                struct dt_key   *key;
                __u64            hash;

                /* fetch 64-bit hash value */
                hash = iops->store(env, it);
                ii->ii_hash_end = hash;

                if (OBD_FAIL_CHECK(OBD_FAIL_OBD_IDX_READ_BREAK)) {
                        if (lip->lip_nr != 0)
                                GOTO(out, rc = 0);
                }

                if (nob < size) {
                        if (lip->lip_nr == 0)
                                GOTO(out, rc = -EINVAL);
                        GOTO(out, rc = 0);
                }

                if ((ii->ii_flags & II_FL_NOHASH) == 0) {
                        /* client wants to the 64-bit hash value associated with
                         * each record */
                        memcpy(tmp_entry, &hash, sizeof(hash));
                        tmp_entry += sizeof(hash);
                }

                /* then the key value */
                LASSERT(iops->key_size(env, it) == ii->ii_keysize);
                key = iops->key(env, it);
                memcpy(tmp_entry, key, ii->ii_keysize);
                tmp_entry += ii->ii_keysize;

                /* and finally the record */
                rc = iops->rec(env, it, (struct dt_rec *)tmp_entry, attr);
                if (rc != -ESTALE) {
                        if (rc != 0)
                                GOTO(out, rc);

                        /* hash/key/record successfully copied! */
                        lip->lip_nr++;
                        if (unlikely(lip->lip_nr == 1 && ii->ii_count == 0))
                                ii->ii_hash_start = hash;
                        entry = tmp_entry + ii->ii_recsize;
                        nob -= size;
                }

                /* move on to the next record */
                do {
                        rc = iops->next(env, it);
                } while (rc == -ESTALE);

        } while (rc == 0);

        GOTO(out, rc);
out:
        if (rc >= 0 && lip->lip_nr > 0)
                /* one more container */
                ii->ii_count++;
        if (rc > 0)
                /* no more entries */
                ii->ii_hash_end = II_END_OFF;
        return rc;
}

/*
 * Walk index and fill lu_page containers with key/record pairs
 *
 * \param env - is the environment passed by the caller
 * \param obj - is the index object to parse
 * \param rdpg - is the lu_rdpg descriptor associated with the transfer
 * \param filler - is the callback function responsible for filling a lu_page
 *               with key/record pairs in the format wanted by the caller
 * \param arg    - is an opaq argument passed to the filler function
 *
 * \retval sum (in bytes) of all filled lu_pages
 * \retval -ve errno on failure
 */
int dt_index_walk(const struct lu_env *env, struct dt_object *obj,
                  const struct lu_rdpg *rdpg, dt_index_page_build_t filler,
                  void *arg)
{
        struct dt_it            *it;
        const struct dt_it_ops  *iops;
        unsigned int             pageidx, nob, nlupgs = 0;
        int                      rc;
        ENTRY;

        LASSERT(rdpg->rp_pages != NULL);
        LASSERT(obj->do_index_ops != NULL);

        nob = rdpg->rp_count;
        if (nob <= 0)
                RETURN(-EFAULT);

        /* Iterate through index and fill containers from @rdpg */
        iops = &obj->do_index_ops->dio_it;
        LASSERT(iops != NULL);
        it = iops->init(env, obj, rdpg->rp_attrs, BYPASS_CAPA);
        if (IS_ERR(it))
                RETURN(PTR_ERR(it));

        rc = iops->load(env, it, rdpg->rp_hash);
        if (rc == 0) {
                /*
                 * Iterator didn't find record with exactly the key requested.
                 *
                 * It is currently either
                 *
                 *     - positioned above record with key less than
                 *     requested---skip it.
                 *     - or not positioned at all (is in IAM_IT_SKEWED
                 *     state)---position it on the next item.
                 */
                rc = iops->next(env, it);
        } else if (rc > 0) {
                rc = 0;
        }

        /* Fill containers one after the other. There might be multiple
         * containers per physical page.
         *
         * At this point and across for-loop:
         *  rc == 0 -> ok, proceed.
         *  rc >  0 -> end of index.
         *  rc <  0 -> error. */
        for (pageidx = 0; rc == 0 && nob > 0; pageidx++) {
                union lu_page   *lp;
                int              i;

                LASSERT(pageidx < rdpg->rp_npages);
                lp = kmap(rdpg->rp_pages[pageidx]);

                /* fill lu pages */
                for (i = 0; i < LU_PAGE_COUNT; i++, lp++, nob -= LU_PAGE_SIZE) {
                        rc = filler(env, lp, min_t(int, nob, LU_PAGE_SIZE),
                                    iops, it, rdpg->rp_attrs, arg);
                        if (rc < 0)
                                break;
                        /* one more lu_page */
                        nlupgs++;
                        if (rc > 0)
                                /* end of index */
                                break;
                }
                kunmap(rdpg->rp_pages[i]);
        }

        iops->put(env, it);
        iops->fini(env, it);

        if (rc >= 0)
                rc = min_t(unsigned int, nlupgs * LU_PAGE_SIZE, rdpg->rp_count);

        RETURN(rc);
}
EXPORT_SYMBOL(dt_index_walk);

/**
 * Walk key/record pairs of an index and copy them into 4KB containers to be
 * transferred over the network. This is the common handler for OBD_IDX_READ
 * RPC processing.
 *
 * \param env - is the environment passed by the caller
 * \param dev - is the dt_device storing the index
 * \param ii  - is the idx_info structure packed by the client in the
 *            OBD_IDX_READ request
 * \param rdpg - is the lu_rdpg descriptor
 *
 * \retval on success, return sum (in bytes) of all filled containers
 * \retval appropriate error otherwise.
 */
int dt_index_read(const struct lu_env *env, struct dt_device *dev,
                  struct idx_info *ii, const struct lu_rdpg *rdpg)
{
        const struct dt_index_features  *feat;
        struct dt_object                *obj;
        int                              rc;
        ENTRY;

        /* rp_count shouldn't be null and should be a multiple of the container
         * size */
        if (rdpg->rp_count <= 0 && (rdpg->rp_count & (LU_PAGE_SIZE - 1)) != 0)
                RETURN(-EFAULT);

        if (fid_seq(&ii->ii_fid) >= FID_SEQ_NORMAL)
                /* we don't support directory transfer via OBD_IDX_READ for the
                 * time being */
                RETURN(-EOPNOTSUPP);

        if (!fid_is_quota(&ii->ii_fid))
                /* block access to all local files except quota files */
                RETURN(-EPERM);

        /* lookup index object subject to the transfer */
        obj = dt_locate(env, dev, &ii->ii_fid);
        if (IS_ERR(obj))
                RETURN(PTR_ERR(obj));
        if (dt_object_exists(obj) == 0)
                GOTO(out, rc = -ENOENT);

        /* fetch index features associated with index object */
        feat = dt_index_feat_select(fid_seq(&ii->ii_fid),
                                    lu_object_attr(&obj->do_lu));
        if (IS_ERR(feat))
                GOTO(out, rc = PTR_ERR(feat));

        /* load index feature if not done already */
        if (obj->do_index_ops == NULL) {
                rc = obj->do_ops->do_index_try(env, obj, feat);
                if (rc)
                        GOTO(out, rc);
        }

        /* fill ii_flags with supported index features */
        ii->ii_flags &= II_FL_NOHASH;

        ii->ii_keysize = feat->dif_keysize_max;
        if ((feat->dif_flags & DT_IND_VARKEY) != 0) {
                /* key size is variable */
                ii->ii_flags |= II_FL_VARKEY;
                /* we don't support variable key size for the time being */
                GOTO(out, rc = -EOPNOTSUPP);
        }

        ii->ii_recsize = feat->dif_recsize_max;
        if ((feat->dif_flags & DT_IND_VARREC) != 0) {
                /* record size is variable */
                ii->ii_flags |= II_FL_VARREC;
                /* we don't support variable record size for the time being */
                GOTO(out, rc = -EOPNOTSUPP);
        }

        if ((feat->dif_flags & DT_IND_NONUNQ) != 0)
                /* key isn't necessarily unique */
                ii->ii_flags |= II_FL_NONUNQ;

        dt_read_lock(env, obj, 0);
        /* fetch object version before walking the index */
        ii->ii_version = dt_version_get(env, obj);

        /* walk the index and fill lu_idxpages with key/record pairs */
        rc = dt_index_walk(env, obj, rdpg, dt_index_page_build ,ii);
        dt_read_unlock(env, obj);

        if (rc == 0) {
                /* index is empty */
                LASSERT(ii->ii_count == 0);
                ii->ii_hash_end = II_END_OFF;
        }

        GOTO(out, rc);
out:
        lu_object_put(env, &obj->do_lu);
        return rc;
}
EXPORT_SYMBOL(dt_index_read);

#ifdef LPROCFS

int lprocfs_dt_rd_blksize(char *page, char **start, off_t off,
                          int count, int *eof, void *data)
{
        struct dt_device *dt = data;
        struct obd_statfs osfs;

        int rc = dt_statfs(NULL, dt, &osfs);
        if (rc == 0) {
                *eof = 1;
                rc = snprintf(page, count, "%u\n",
                                (unsigned) osfs.os_bsize);
        }

        return rc;
}
EXPORT_SYMBOL(lprocfs_dt_rd_blksize);

int lprocfs_dt_rd_kbytestotal(char *page, char **start, off_t off,
                              int count, int *eof, void *data)
{
        struct dt_device *dt = data;
        struct obd_statfs osfs;

        int rc = dt_statfs(NULL, dt, &osfs);
        if (rc == 0) {
                __u32 blk_size = osfs.os_bsize >> 10;
                __u64 result = osfs.os_blocks;

                while (blk_size >>= 1)
                        result <<= 1;

                *eof = 1;
                rc = snprintf(page, count, LPU64"\n", result);
        }

        return rc;
}
EXPORT_SYMBOL(lprocfs_dt_rd_kbytestotal);

int lprocfs_dt_rd_kbytesfree(char *page, char **start, off_t off,
                             int count, int *eof, void *data)
{
        struct dt_device *dt = data;
        struct obd_statfs osfs;

        int rc = dt_statfs(NULL, dt, &osfs);
        if (rc == 0) {
                __u32 blk_size = osfs.os_bsize >> 10;
                __u64 result = osfs.os_bfree;

                while (blk_size >>= 1)
                        result <<= 1;

                *eof = 1;
                rc = snprintf(page, count, LPU64"\n", result);
        }

        return rc;
}
EXPORT_SYMBOL(lprocfs_dt_rd_kbytesfree);

int lprocfs_dt_rd_kbytesavail(char *page, char **start, off_t off,
                              int count, int *eof, void *data)
{
        struct dt_device *dt = data;
        struct obd_statfs osfs;

        int rc = dt_statfs(NULL, dt, &osfs);
        if (rc == 0) {
                __u32 blk_size = osfs.os_bsize >> 10;
                __u64 result = osfs.os_bavail;

                while (blk_size >>= 1)
                        result <<= 1;

                *eof = 1;
                rc = snprintf(page, count, LPU64"\n", result);
        }

        return rc;
}
EXPORT_SYMBOL(lprocfs_dt_rd_kbytesavail);

int lprocfs_dt_rd_filestotal(char *page, char **start, off_t off,
                             int count, int *eof, void *data)
{
        struct dt_device *dt = data;
        struct obd_statfs osfs;

        int rc = dt_statfs(NULL, dt, &osfs);
        if (rc == 0) {
                *eof = 1;
                rc = snprintf(page, count, LPU64"\n", osfs.os_files);
        }

        return rc;
}
EXPORT_SYMBOL(lprocfs_dt_rd_filestotal);

int lprocfs_dt_rd_filesfree(char *page, char **start, off_t off,
                            int count, int *eof, void *data)
{
        struct dt_device *dt = data;
        struct obd_statfs osfs;

        int rc = dt_statfs(NULL, dt, &osfs);
        if (rc == 0) {
                *eof = 1;
                rc = snprintf(page, count, LPU64"\n", osfs.os_ffree);
        }

        return rc;
}
EXPORT_SYMBOL(lprocfs_dt_rd_filesfree);

#endif /* LPROCFS */