/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
 * vim:expandtab:shiftwidth=8:tabstop=8:
 *
 * 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 [sun.com URL with a
 * copy of GPLv2].
 *
 * 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  2008 Sun Microsystems, Inc. All rights reserved
 * Use is subject to license terms.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * iam_lvar.c
 *
 * implementation of iam format for fixed size records, variable sized keys.
 *
 * Author: Nikita Danilov <nikita@clusterfs.com>
 */

#include <linux/types.h>
#include "osd_internal.h"

/*
 * Leaf operations.
 */

enum {
        IAM_LVAR_LEAF_MAGIC = 0x1973 /* This is duplicated in
                                      * lustre/utils/create_iam.c */
};

/* This is duplicated in lustre/utils/create_iam.c */
struct lvar_leaf_header {
        __le16 vlh_magic; /* magic number IAM_LVAR_LEAF_MAGIC */
        __le16 vlh_used;  /* used bytes, including header */
};

/*
 * Format of leaf entry:
 *
 * __le16 keysize
 *     u8 key[keysize]
 *     u8 record[rec_size]
 *
 * Entries are ordered in key order.
 */

/* This is duplicated in lustre/utils/create_iam.c */
typedef __u32 lvar_hash_t;

/* This is duplicated in lustre/utils/create_iam.c */
struct lvar_leaf_entry {
        __le32 vle_hash;
        __le16 vle_keysize;
        u8     vle_key[0];
};

#define PDIFF(ptr0, ptr1) (((char *)(ptr0)) - ((char *)(ptr1)))


static inline int blocksize(const struct iam_leaf *leaf)
{
        return iam_leaf_container(leaf)->ic_object->i_sb->s_blocksize;
}

static inline const char *kchar(const struct iam_key *key)
{
        return (void *)key;
}

static inline struct iam_lentry *lvar_lentry(const struct lvar_leaf_entry *ent)
{
        return (struct iam_lentry *)ent;
}

static inline struct lvar_leaf_entry *lentry_lvar(const struct iam_lentry *lent)
{
        return (struct lvar_leaf_entry *)lent;
}


static inline int e_keysize(const struct lvar_leaf_entry *ent)
{
        return le16_to_cpu(ent->vle_keysize);
}

/* This is duplicated in lustre/utils/create_iam.c */
enum {
        LVAR_PAD   = 4,
        LVAR_ROUND = LVAR_PAD - 1
};

static inline int getsize(const struct iam_leaf *leaf, int namelen, int recsize)
{
        CLASSERT(!(LVAR_PAD & (LVAR_PAD - 1)));

        return (offsetof(struct lvar_leaf_entry, vle_key) +
                namelen + recsize + LVAR_ROUND) & ~LVAR_ROUND;
}

static inline int rec_size(const struct iam_rec *rec)
{
        return *(const char *)rec;
}

static inline struct iam_rec *e_rec(const struct lvar_leaf_entry *ent)
{
        return ((void *)ent) +
                offsetof(struct lvar_leaf_entry, vle_key) + e_keysize(ent);
}

static inline int e_size(const struct iam_leaf *leaf,
                         const struct lvar_leaf_entry *ent)
{
        return getsize(leaf, e_keysize(ent), rec_size(e_rec(ent)));
}

static inline char *e_char(const struct lvar_leaf_entry *ent)
{
        return (char *)&ent->vle_key;
}

static inline struct iam_key *e_key(const struct lvar_leaf_entry *ent)
{
        return (struct iam_key *)e_char(ent);
}

static inline lvar_hash_t e_hash(const struct lvar_leaf_entry *ent)
{
        return le32_to_cpu(ent->vle_hash);
}

static void e_print(const struct lvar_leaf_entry *ent)
{
        printk("        %p %8.8x \"%*.*s\"\n", ent, e_hash(ent),
               e_keysize(ent), e_keysize(ent), e_char(ent));
}
#if 0
static int e_check(const struct iam_leaf *leaf,
                   const struct lvar_leaf_entry *ent)
{
        const void *point = ent;
        const void *start = leaf->il_bh->b_data;
        return
                start + sizeof(struct lvar_leaf_header) <= point &&
                point + e_size(leaf, ent) < start + blocksize(leaf);
}
#endif

static inline struct lvar_leaf_entry *e_next(const struct iam_leaf *leaf,
                                             const struct lvar_leaf_entry *ent)
{
        return ((void *)ent) + e_size(leaf, ent);
}

#define LVAR_HASH_SANDWICH  (0)
#define LVAR_HASH_TEA       (1)
#define LVAR_HASH_R5        (0)
#define LVAR_HASH_PREFIX    (0)

static __u32 hash_build0(const char *name, int namelen)
{
        __u32 result;

        if (namelen == 0)
                return 0;
        if (strncmp(name, ".", 1) == 0 && namelen == 1)
                return 1;
        if (strncmp(name, "..", 2) == 0 && namelen == 2)
                return 2;

        if (LVAR_HASH_PREFIX) {
                result = 0;
                strncpy((void *)&result,
                        name, min(namelen, (int)sizeof result));
        } else {
                struct ldiskfs_dx_hash_info hinfo;

                hinfo.hash_version = LDISKFS_DX_HASH_TEA;
                hinfo.seed = 0;
                ldiskfsfs_dirhash(name, namelen, &hinfo);
                result = hinfo.hash;
                if (LVAR_HASH_SANDWICH) {
                        __u32 result2;

                        hinfo.hash_version = LDISKFS_DX_HASH_TEA;
                        hinfo.seed = 0;
                        ldiskfsfs_dirhash(name, namelen, &hinfo);
                        result2 = hinfo.hash;
                        result = (0xfc000000 & result2) | (0x03ffffff & result);
                }
        }
        return result;
}

enum {
        HASH_GRAY_AREA = 1024,
        HASH_MAX_SIZE  = 0x7fffffffUL
};

static __u32 hash_build(const char *name, int namelen)
{
        __u32 hash;

        hash = (hash_build0(name, namelen) << 1) & HASH_MAX_SIZE;
        if (hash > HASH_MAX_SIZE - HASH_GRAY_AREA)
                hash &= HASH_GRAY_AREA - 1;
        return hash;
}

static inline lvar_hash_t get_hash(const struct iam_container *bag,
                                   const char *name, int namelen)
{
        return hash_build(name, namelen);
}

static inline int e_eq(const struct lvar_leaf_entry *ent,
                       const char *name, int namelen)
{
        return namelen == e_keysize(ent) && !memcmp(e_char(ent), name, namelen);
}

static inline int e_cmp(const struct iam_leaf *leaf,
                        const struct lvar_leaf_entry *ent, lvar_hash_t hash)
{
        lvar_hash_t ehash;

        ehash = e_hash(ent);
        return ehash == hash ? 0 : (ehash < hash ? -1 : +1);
}

static struct lvar_leaf_header *n_head(const struct iam_leaf *l)
{
        return (struct lvar_leaf_header *)l->il_bh->b_data;
}

static int h_used(const struct lvar_leaf_header *hdr)
{
        return le16_to_cpu(hdr->vlh_used);
}

static void h_used_adj(const struct iam_leaf *leaf,
                       struct lvar_leaf_header *hdr, int adj)
{
        int used;

        used = h_used(hdr) + adj;
        assert_corr(sizeof *hdr <= used && used <= blocksize(leaf));
        hdr->vlh_used = cpu_to_le16(used);
}

static struct lvar_leaf_entry *n_start(const struct iam_leaf *leaf)
{
        return (void *)leaf->il_bh->b_data + sizeof(struct lvar_leaf_header);
}

static struct lvar_leaf_entry *n_end(const struct iam_leaf *l)
{
        return (void *)l->il_bh->b_data + h_used(n_head(l));
}

static struct lvar_leaf_entry *n_cur(const struct iam_leaf *l)
{
        return lentry_lvar(l->il_at);
}

void n_print(const struct iam_leaf *l)
{
        struct lvar_leaf_entry *scan;

        printk(CFS_KERN_EMERG "used: %d\n", h_used(n_head(l)));
        for (scan = n_start(l); scan < n_end(l); scan = e_next(l, scan))
                e_print(scan);
}

#if LDISKFS_CORRECTNESS_ON
static int n_at_rec(const struct iam_leaf *folio)
{
        return
                n_start(folio) <= lentry_lvar(folio->il_at) &&
                lentry_lvar(folio->il_at) < n_end(folio);
}

#if LDISKFS_INVARIANT_ON
static int n_invariant(const struct iam_leaf *leaf)
{
        struct iam_path        *path;
        struct lvar_leaf_entry *scan;
        struct lvar_leaf_entry *end;
        lvar_hash_t             hash;
        lvar_hash_t             nexthash;
        lvar_hash_t             starthash;

        end  = n_end(leaf);
        hash = 0;
        path = leaf->il_path;

        if (h_used(n_head(leaf)) > blocksize(leaf))
                return 0;

        /*
         * Delimiting key in the parent index node. Clear least bit to account
         * for hash collision marker.
         */
        starthash = *(lvar_hash_t *)iam_ikey_at(path, path->ip_frame->at) & ~1;
        for (scan = n_start(leaf); scan < end; scan = e_next(leaf, scan)) {
                nexthash = e_hash(scan);
                if (nexthash != get_hash(iam_leaf_container(leaf),
                                         e_char(scan), e_keysize(scan))) {
                        BREAKPOINT();
                        return 0;
                }
                if (0 && nexthash < starthash) {
                        /*
                         * Unfortunately this useful invariant cannot be
                         * reliably checked as parent node is nor necessarily
                         * locked.
                         */
                        n_print(leaf);
                        printk("%#x < %#x\n", nexthash, starthash);
                        dump_stack();
                        return 0;
                }
                if (nexthash < hash) {
                        BREAKPOINT();
                        return 0;
                }
                hash = nexthash;
        }
        if (scan != end) {
                BREAKPOINT();
                return 0;
        }
        return 1;
}
/* LDISKFS_INVARIANT_ON */
#endif

/* LDISKFS_CORRECTNESS_ON */
#endif

static struct iam_ikey *lvar_ikey(const struct iam_leaf *l,
                                  struct iam_ikey *key)
{
        lvar_hash_t *hash;

        assert_corr(n_at_rec(l));

        hash = (void *)key;
        *hash = e_hash(n_cur(l));
        return key;
}

static struct iam_key *lvar_key(const struct iam_leaf *l)
{
        return e_key(n_cur(l));
}

static int lvar_key_size(const struct iam_leaf *l)
{
        return e_keysize(n_cur(l));
}

static void lvar_start(struct iam_leaf *l)
{
        l->il_at = lvar_lentry(n_start(l));
}

static int lvar_init(struct iam_leaf *l)
{
        int result;
        int used;
        struct lvar_leaf_header *head;

        assert_corr(l->il_bh != NULL);

        head = n_head(l);
        used = h_used(head);
        if (head->vlh_magic == le16_to_cpu(IAM_LVAR_LEAF_MAGIC) &&
            used <= blocksize(l)) {
                l->il_at = l->il_entries = lvar_lentry(n_start(l));
                result = 0;
        } else {
                struct inode *obj;

                obj = iam_leaf_container(l)->ic_object;
                CERROR("Wrong magic in node %llu (#%lu): %#x != %#x or "
                       "wrong used: %i",
                       (unsigned long long)l->il_bh->b_blocknr, obj->i_ino,
                       head->vlh_magic, le16_to_cpu(IAM_LVAR_LEAF_MAGIC),
                       used);
                result = -EIO;
        }
        return result;
}

static void lvar_fini(struct iam_leaf *l)
{
        l->il_entries = l->il_at = NULL;
}

struct iam_rec *lvar_rec(const struct iam_leaf *l)
{
        assert_corr(n_at_rec(l));
        return e_rec(n_cur(l));
}

static void lvar_next(struct iam_leaf *l)
{
        assert_corr(n_at_rec(l));
        assert_corr(iam_leaf_is_locked(l));
        l->il_at = lvar_lentry(e_next(l, n_cur(l)));
}

static int lvar_lookup(struct iam_leaf *leaf, const struct iam_key *k)
{
        struct lvar_leaf_entry *found;
        struct lvar_leaf_entry *scan;
        struct lvar_leaf_entry *end;
        int                     result;
        const char             *name;
        int                     namelen;
        int                     found_equal;
        lvar_hash_t             hash;
        int                     last;

        assert_inv(n_invariant(leaf));
        end = n_end(leaf);

        name = kchar(k);
        namelen = strlen(name);
        hash = get_hash(iam_leaf_container(leaf), name, namelen);
        found = NULL;
        found_equal = 0;
        last = 1;

        for (scan = n_start(leaf); scan < end; scan = e_next(leaf, scan)) {
                lvar_hash_t scan_hash;

                scan_hash = e_hash(scan);
                if (scan_hash < hash)
                        found = scan;
                else if (scan_hash == hash) {
                        if (e_eq(scan, name, namelen)) {
                                /*
                                 * perfect match
                                 */
                                leaf->il_at = lvar_lentry(scan);
                                return IAM_LOOKUP_EXACT;
                        } else if (!found_equal) {
                                        found = scan;
                                        found_equal = 1;
                        }
                } else {
                        last = 0;
                        break;
                }
        }
        if (found == NULL) {
                /*
                 * @k is less than all hashes in the leaf.
                 */
                lvar_start(leaf);
                result = IAM_LOOKUP_BEFORE;
        } else {
                leaf->il_at = lvar_lentry(found);
                result = IAM_LOOKUP_OK;
                assert_corr(n_at_rec(leaf));
        }
        if (last)
                result |= IAM_LOOKUP_LAST;
        assert_inv(n_invariant(leaf));

        return result;
}

static int lvar_ilookup(struct iam_leaf *leaf, const struct iam_ikey *ik)
{
        struct lvar_leaf_entry *scan;
        struct lvar_leaf_entry *end;
        lvar_hash_t             hash;

        assert_inv(n_invariant(leaf));
        end  = n_end(leaf);
        hash = *(const lvar_hash_t *)ik;

        lvar_start(leaf);
        for (scan = n_start(leaf); scan < end; scan = e_next(leaf, scan)) {
                lvar_hash_t scan_hash;

                scan_hash = e_hash(scan);
                if (scan_hash > hash)
                        return scan == n_start(leaf) ?
                                IAM_LOOKUP_BEFORE : IAM_LOOKUP_OK;
                leaf->il_at = lvar_lentry(scan);
                if (scan_hash == hash)
                        return IAM_LOOKUP_EXACT;
        }
        assert_inv(n_invariant(leaf));
        /*
         * @ik is greater than any key in the node. Return last record in the
         * node.
         */
        return IAM_LOOKUP_OK;
}

static void __lvar_key_set(struct iam_leaf *l, const struct iam_key *k)
{
        memcpy(e_key(n_cur(l)), k, e_keysize(n_cur(l)));
}

static void lvar_key_set(struct iam_leaf *l, const struct iam_key *k)
{
        assert_corr(n_at_rec(l));
        assert_corr(strlen(kchar(k)) == e_keysize(n_cur(l)));
        assert_corr(iam_leaf_is_locked(l));
        __lvar_key_set(l, k);
        assert_inv(n_invariant(l));
}

static int lvar_key_cmp(const struct iam_leaf *l, const struct iam_key *k)
{
        lvar_hash_t hash;
        const char *name;

        name = kchar(k);

        hash = get_hash(iam_leaf_container(l), name, strlen(name));
        return e_cmp(l, n_cur(l), hash);
}

static int lvar_key_eq(const struct iam_leaf *l, const struct iam_key *k)
{
        const char *name;

        name = kchar(k);
        return e_eq(n_cur(l), name, strlen(name));
}

static void __lvar_rec_set(struct iam_leaf *l, const struct iam_rec *r)
{
        memcpy(e_rec(n_cur(l)), r, rec_size(r));
}

static void lvar_rec_set(struct iam_leaf *l, const struct iam_rec *r)
{
        assert_corr(n_at_rec(l));
        assert_corr(iam_leaf_is_locked(l));
        __lvar_rec_set(l, r);
        assert_inv(n_invariant(l));
}

static void lvar_rec_get(const struct iam_leaf *l, struct iam_rec *r)
{
        struct iam_rec *rec;

        rec = e_rec(n_cur(l));
        assert_corr(n_at_rec(l));
        assert_corr(iam_leaf_is_locked(l));
        memcpy(r, rec, rec_size(rec));
        assert_inv(n_invariant(l));
}

static int lvar_can_add(const struct iam_leaf *l,
                        const struct iam_key *k, const struct iam_rec *r)
{
        assert_corr(iam_leaf_is_locked(l));
        return
                h_used(n_head(l)) +
                getsize(l, strlen(kchar(k)), rec_size(r)) <= blocksize(l);
}

static int lvar_at_end(const struct iam_leaf *folio)
{
        assert_corr(iam_leaf_is_locked(folio));
        return n_cur(folio) == n_end(folio);
}

static void lvar_rec_add(struct iam_leaf *leaf,
                         const struct iam_key *k, const struct iam_rec *r)
{
        const char *key;
        int   ksize;
        int   shift;
        void *end;
        void *start;
        ptrdiff_t diff;

        assert_corr(lvar_can_add(leaf, k, r));
        assert_inv(n_invariant(leaf));
        assert_corr(iam_leaf_is_locked(leaf));

        key   = kchar(k);
        ksize = strlen(key);
        shift = getsize(leaf, ksize, rec_size(r));

        if (!lvar_at_end(leaf)) {
                assert_corr(n_cur(leaf) < n_end(leaf));
                end = n_end(leaf);
                if (lvar_key_cmp(leaf, k) <= 0)
                        lvar_next(leaf);
                else
                        /*
                         * Another exceptional case: insertion with the key
                         * less than least key in the leaf.
                         */
                        assert_corr(leaf->il_at == leaf->il_entries);

                start = leaf->il_at;
                diff  = PDIFF(end, start);
                assert_corr(diff >= 0);
                memmove(start + shift, start, diff);
        }
        h_used_adj(leaf, n_head(leaf), shift);
        n_cur(leaf)->vle_keysize = cpu_to_le16(ksize);
        n_cur(leaf)->vle_hash = cpu_to_le32(get_hash(iam_leaf_container(leaf),
                                                     key, ksize));
        __lvar_key_set(leaf, k);
        __lvar_rec_set(leaf, r);
        assert_corr(n_at_rec(leaf));
        assert_inv(n_invariant(leaf));
}

static void lvar_rec_del(struct iam_leaf *leaf, int shift)
{
        void *next;
        void *end;
        int nob;

        assert_corr(n_at_rec(leaf));
        assert_inv(n_invariant(leaf));
        assert_corr(iam_leaf_is_locked(leaf));

        end  = n_end(leaf);
        next = e_next(leaf, n_cur(leaf));
        nob  = e_size(leaf, n_cur(leaf));
        memmove(leaf->il_at, next, end - next);
        h_used_adj(leaf, n_head(leaf), -nob);
        assert_inv(n_invariant(leaf));
}

static void lvar_init_new(struct iam_container *c, struct buffer_head *bh)
{
        struct lvar_leaf_header *hdr;

        hdr = (struct lvar_leaf_header *)bh->b_data;
        hdr->vlh_magic = cpu_to_le16(IAM_LVAR_LEAF_MAGIC);
        hdr->vlh_used  = sizeof *hdr;
}

static struct lvar_leaf_entry *find_pivot(const struct iam_leaf *leaf,
                                          struct lvar_leaf_entry **prev)
{
        void *scan;
        void *start;
        int threshold;

        *prev = NULL;
        threshold = blocksize(leaf) / 2;
        for (scan = start = n_start(leaf); scan - start <= threshold;
             *prev = scan, scan = e_next(leaf, scan)) {
                ;
        }
        return scan;
}

static void lvar_split(struct iam_leaf *leaf, struct buffer_head **bh,
                       iam_ptr_t new_blknr)
{
        struct lvar_leaf_entry  *first_to_move;
        struct lvar_leaf_entry  *last_to_stay;
        struct iam_path         *path;
        struct lvar_leaf_header *hdr;
        struct buffer_head      *new_leaf;

        ptrdiff_t   tomove;
        lvar_hash_t hash;

        assert_inv(n_invariant(leaf));
        assert_corr(iam_leaf_is_locked(leaf));

        new_leaf = *bh;
        path = iam_leaf_path(leaf);

        hdr = (void *)new_leaf->b_data;

        first_to_move = find_pivot(leaf, &last_to_stay);
        assert_corr(last_to_stay != NULL);
        assert_corr(e_next(leaf, last_to_stay) == first_to_move);

        hash = e_hash(first_to_move);
        if (hash == e_hash(last_to_stay))
                /*
                 * Duplicate hash.
                 */
                hash |= 1;

        tomove = PDIFF(n_end(leaf), first_to_move);
        memmove(hdr + 1, first_to_move, tomove);

        h_used_adj(leaf, hdr, tomove);
        h_used_adj(leaf, n_head(leaf), -tomove);

        assert_corr(n_end(leaf) == first_to_move);

        if (n_cur(leaf) >= first_to_move) {
                /*
                 * insertion point moves into new leaf.
                 */
                ptrdiff_t shift;
                int result;

                shift = PDIFF(leaf->il_at, first_to_move);
                *bh = leaf->il_bh;
                leaf->il_bh = new_leaf;
                leaf->il_curidx = new_blknr;

                assert_corr(iam_leaf_is_locked(leaf));
                result = lvar_init(leaf);
                /*
                 * init cannot fail, as node was just initialized.
                 */
                assert_corr(result == 0);
                leaf->il_at = ((void *)leaf->il_at) + shift;
        }
        /*
         * Insert pointer to the new node (together with the least key in
         * the node) into index node.
         */
        iam_insert_key_lock(path, path->ip_frame, (struct iam_ikey *)&hash,
                            new_blknr);
        assert_corr(n_cur(leaf) < n_end(leaf));
        assert_inv(n_invariant(leaf));
}

static struct iam_leaf_operations lvar_leaf_ops = {
        .init           = lvar_init,
        .init_new       = lvar_init_new,
        .fini           = lvar_fini,
        .start          = lvar_start,
        .next           = lvar_next,
        .key            = lvar_key,
        .ikey           = lvar_ikey,
        .rec            = lvar_rec,
        .key_set        = lvar_key_set,
        .key_cmp        = lvar_key_cmp,
        .key_eq         = lvar_key_eq,
        .key_size       = lvar_key_size,
        .rec_set        = lvar_rec_set,
        .rec_get        = lvar_rec_get,
        .lookup         = lvar_lookup,
        .ilookup        = lvar_ilookup,
        .at_end         = lvar_at_end,
        .rec_add        = lvar_rec_add,
        .rec_del        = lvar_rec_del,
        .can_add        = lvar_can_add,
        .split          = lvar_split
};

/*
 * Index operations.
 */

enum {
        /* This is duplicated in lustre/utils/create_iam.c */
        /* egrep -i '^o?x?[olabcdef]*$' /usr/share/dict/words */
        IAM_LVAR_ROOT_MAGIC = 0xb01dface
};

/* This is duplicated in lustre/utils/create_iam.c */
struct lvar_root {
        __le32 vr_magic;
        __le16 vr_recsize;
        __le16 vr_ptrsize;
        u8     vr_indirect_levels;
        u8     vr_padding0;
        __le16 vr_padding1;
};

static __u32 lvar_root_ptr(struct iam_container *c)
{
        return 0;
}

static int lvar_node_init(struct iam_container *c, struct buffer_head *bh,
                          int root)
{
        return 0;
}

static struct iam_entry *lvar_root_inc(struct iam_container *c,
                                       struct iam_path *path,
                                       struct iam_frame *frame)
{
        struct lvar_root *root;
        struct iam_entry *entries;

        assert_corr(iam_frame_is_locked(path, frame));
        entries = frame->entries;

        dx_set_count(entries, 2);
        assert_corr(dx_get_limit(entries) == dx_root_limit(path));

        root = (void *)frame->bh->b_data;
        assert_corr(le64_to_cpu(root->vr_magic) == IAM_LVAR_ROOT_MAGIC);
        root->vr_indirect_levels ++;
        frame->at = entries = iam_entry_shift(path, entries, 1);
        memset(iam_ikey_at(path, entries), 0,
               iam_path_descr(path)->id_ikey_size);
        return entries;
}

static int lvar_node_check(struct iam_path *path, struct iam_frame *frame)
{
        unsigned count;
        unsigned limit;
        unsigned limit_correct;
        struct iam_entry *entries;

        entries = dx_node_get_entries(path, frame);

        if (frame == path->ip_frames) {
                struct lvar_root *root;

                root = (void *)frame->bh->b_data;
                if (le64_to_cpu(root->vr_magic) != IAM_LVAR_ROOT_MAGIC)
                        return -EIO;
                limit_correct = dx_root_limit(path);
        } else
                limit_correct = dx_node_limit(path);
        count = dx_get_count(entries);
        limit = dx_get_limit(entries);
        if (count > limit)
                return -EIO;
        if (limit != limit_correct)
                return -EIO;
        return 0;
}

static int lvar_node_load(struct iam_path *path, struct iam_frame *frame)
{
        struct iam_entry *entries;
        void *data;
        entries = dx_node_get_entries(path, frame);

        data = frame->bh->b_data;

        if (frame == path->ip_frames) {
                struct lvar_root *root;
                const char *name;

                root = data;
                name = kchar(path->ip_key_target);
                path->ip_indirect = root->vr_indirect_levels;
                if (path->ip_ikey_target == NULL) {
                        path->ip_ikey_target = iam_path_ikey(path, 4);
                        *(lvar_hash_t *)path->ip_ikey_target =
                                get_hash(path->ip_container, name,
                                         strlen(name));
                }
        }
        frame->entries = frame->at = entries;
        return 0;
}

static int lvar_ikeycmp(const struct iam_container *c,
                        const struct iam_ikey *k1, const struct iam_ikey *k2)
{
        lvar_hash_t p1 = le32_to_cpu(*(lvar_hash_t *)k1);
        lvar_hash_t p2 = le32_to_cpu(*(lvar_hash_t *)k2);

        return p1 > p2 ? +1 : (p1 < p2 ? -1 : 0);
}

static struct iam_path_descr *lvar_ipd_alloc(const struct iam_container *c,
                                             void *area)
{
        return iam_ipd_alloc(area, c->ic_descr->id_ikey_size);
}

static void lvar_root(void *buf,
                      int blocksize, int keysize, int ptrsize, int recsize)
{
        struct lvar_root *root;
        struct dx_countlimit *limit;
        void                 *entry;
        int isize;

        isize = sizeof(lvar_hash_t) + ptrsize;
        root = buf;
        *root = (typeof(*root)) {
                .vr_magic            = cpu_to_le32(IAM_LVAR_ROOT_MAGIC),
                .vr_recsize          = cpu_to_le16(recsize),
                .vr_ptrsize          = cpu_to_le16(ptrsize),
                .vr_indirect_levels  = 0
        };

        limit = (void *)(root + 1);
        *limit = (typeof(*limit)){
                /*
                 * limit itself + one pointer to the leaf.
                 */
                .count = cpu_to_le16(2),
                .limit = iam_root_limit(sizeof(struct lvar_root), blocksize,
                                        sizeof (lvar_hash_t) + ptrsize)
        };

        entry = root + 1;
        /*
         * Skip over @limit.
         */
        entry += isize;

        /*
         * Entry format is <key> followed by <ptr>. In the minimal tree
         * consisting of a root and single node, <key> is a minimal possible
         * key.
         */
        *(lvar_hash_t *)entry = 0;
        entry += sizeof(lvar_hash_t);
        /* now @entry points to <ptr> */
        if (ptrsize == 4)
                *(u_int32_t *)entry = cpu_to_le32(1);
        else
                *(u_int64_t *)entry = cpu_to_le64(1);
}

static int lvar_esize(int namelen, int recsize)
{
        return (offsetof(struct lvar_leaf_entry, vle_key) +
                namelen + recsize + LVAR_ROUND) & ~LVAR_ROUND;
}

static void lvar_leaf(void *buf,
                      int blocksize, int keysize, int ptrsize, int recsize)
{
        struct lvar_leaf_header *head;
        struct lvar_leaf_entry  *entry;

        /* form leaf */
        head = buf;
        *head = (typeof(*head)) {
                .vlh_magic = cpu_to_le16(IAM_LVAR_LEAF_MAGIC),
                .vlh_used  = cpu_to_le16(sizeof *head + lvar_esize(0, recsize))
        };
        entry = (void *)(head + 1);
        *entry = (typeof(*entry)) {
                .vle_hash    = 0,
                .vle_keysize = 0
        };
        memset(e_rec(entry), 0, recsize);
        *(char *)e_rec(entry) = recsize;
}

int iam_lvar_create(struct inode *obj,
                    int keysize, int ptrsize, int recsize, handle_t *handle)
{
        struct buffer_head *root_node;
        struct buffer_head *leaf_node;
        struct super_block *sb;

        u32 blknr;
        int result;
        unsigned long bsize;

        assert_corr(obj->i_size == 0);

        sb = obj->i_sb;
        bsize = sb->s_blocksize;
        root_node = ldiskfs_append(handle, obj, &blknr, &result);
        leaf_node = ldiskfs_append(handle, obj, &blknr, &result);
        if (root_node != NULL && leaf_node != NULL) {
                lvar_root(root_node->b_data, bsize, keysize, ptrsize, recsize);
                lvar_leaf(leaf_node->b_data, bsize, keysize, ptrsize, recsize);
                ldiskfs_mark_inode_dirty(handle, obj);
                result = ldiskfs_journal_dirty_metadata(handle, root_node);
                if (result == 0)
                        result = ldiskfs_journal_dirty_metadata(handle, leaf_node);
                if (result != 0)
                        ldiskfs_std_error(sb, result);
        }
        brelse(leaf_node);
        brelse(root_node);
        return result;
}
EXPORT_SYMBOL(iam_lvar_create);

static struct iam_operations lvar_ops = {
        .id_root_ptr    = lvar_root_ptr,
        .id_node_read   = iam_node_read,
        .id_node_init   = lvar_node_init,
        .id_node_check  = lvar_node_check,
        .id_node_load   = lvar_node_load,
        .id_ikeycmp     = lvar_ikeycmp,
        .id_root_inc    = lvar_root_inc,
        .id_ipd_alloc   = lvar_ipd_alloc,
        .id_ipd_free    = iam_ipd_free,
        .id_name        = "lvar"
};

static int lvar_guess(struct iam_container *c)
{
        int result;
        struct buffer_head *bh;
        const struct lvar_root *root;

        assert_corr(c->ic_object != NULL);

        result = iam_node_read(c, lvar_root_ptr(c), NULL, &bh);
        if (result == 0) {
                root = (void *)bh->b_data;
                if (le64_to_cpu(root->vr_magic) == IAM_LVAR_ROOT_MAGIC) {
                        struct iam_descr *descr;

                        descr = c->ic_descr;
                        descr->id_key_size  = LDISKFS_NAME_LEN;
                        descr->id_ikey_size = sizeof (lvar_hash_t);
                        descr->id_rec_size  = le16_to_cpu(root->vr_recsize);
                        descr->id_ptr_size  = le16_to_cpu(root->vr_ptrsize);
                        descr->id_root_gap  = sizeof *root;
                        descr->id_node_gap  = 0;
                        descr->id_ops       = &lvar_ops;
                        descr->id_leaf_ops  = &lvar_leaf_ops;
                } else
                        result = -EBADF;
                brelse(bh);
        }
        return result;
}

static struct iam_format lvar_format = {
        .if_guess = lvar_guess
};

void iam_lvar_format_init(void)
{
        iam_format_register(&lvar_format);
}