fs/zfs/zap_micro.c

	zap_micro.c revision c5f9e43110e1fb316fc4297c2d150b3518b80bbe
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/spa.h>
#include <sys/dmu.h>
#include <sys/zfs_context.h>
#include <sys/zap.h>
#include <sys/refcount.h>
#include <sys/zap_impl.h>
#include <sys/zap_leaf.h>
#include <sys/avl.h>
#include <sys/zfs_i18n.h>

static void mzap_upgrade(zap_t *zap, dmu_tx_t *tx);


static uint64_t
zap_hash(zap_t *zap, const char *normname)
{
    const uint8_t *cp;
    uint8_t c;
    uint64_t crc = zap->zap_salt;

    /* NB: name must already be normalized, if necessary */

    ASSERT(crc != 0);
    ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
    for (cp = (const uint8_t *)normname; (c = *cp) != '\0'; cp++) {
        crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ c) & 0xFF];
    }

    /*
     * Only use 28 bits, since we need 4 bits in the cookie for the
     * collision differentiator.  We MUST use the high bits, since
     * those are the ones that we first pay attention to when
     * chosing the bucket.
     */
    crc &= ~((1ULL << (64 - ZAP_HASHBITS)) - 1);

    return (crc);
}

static int
zap_normalize(zap_t *zap, const char *name, char *namenorm)
{
    size_t inlen, outlen;
    int err;

    inlen = strlen(name) + 1;
    outlen = ZAP_MAXNAMELEN;

    err = 0;
    (void) u8_textprep_str((char *)name, &inlen, namenorm, &outlen,
        zap->zap_normflags | U8_TEXTPREP_IGNORE_NULL, U8_UNICODE_LATEST,
        &err);

    return (err);
}

boolean_t
zap_match(zap_name_t *zn, const char *matchname)
{
    if (zn->zn_matchtype == MT_FIRST) {
        char norm[ZAP_MAXNAMELEN];

        if (zap_normalize(zn->zn_zap, matchname, norm) != 0)
            return (B_FALSE);

        return (strcmp(zn->zn_name_norm, norm) == 0);
    } else {
        /* MT_BEST or MT_EXACT */
        return (strcmp(zn->zn_name_orij, matchname) == 0);
    }
}

void
zap_name_free(zap_name_t *zn)
{
    kmem_free(zn, sizeof (zap_name_t));
}

/* XXX combine this with zap_lockdir()? */
zap_name_t *
zap_name_alloc(zap_t *zap, const char *name, matchtype_t mt)
{
    zap_name_t *zn = kmem_alloc(sizeof (zap_name_t), KM_SLEEP);

    zn->zn_zap = zap;
    zn->zn_name_orij = name;
    zn->zn_matchtype = mt;
    if (zap->zap_normflags) {
        if (zap_normalize(zap, name, zn->zn_normbuf) != 0) {
            zap_name_free(zn);
            return (NULL);
        }
        zn->zn_name_norm = zn->zn_normbuf;
    } else {
        if (mt != MT_EXACT) {
            zap_name_free(zn);
            return (NULL);
        }
        zn->zn_name_norm = zn->zn_name_orij;
    }

    zn->zn_hash = zap_hash(zap, zn->zn_name_norm);
    return (zn);
}

static void
mzap_byteswap(mzap_phys_t *buf, size_t size)
{
    int i, max;
    buf->mz_block_type = BSWAP_64(buf->mz_block_type);
    buf->mz_salt = BSWAP_64(buf->mz_salt);
    max = (size / MZAP_ENT_LEN) - 1;
    for (i = 0; i < max; i++) {
        buf->mz_chunk[i].mze_value =
            BSWAP_64(buf->mz_chunk[i].mze_value);
        buf->mz_chunk[i].mze_cd =
            BSWAP_32(buf->mz_chunk[i].mze_cd);
    }
}

void
zap_byteswap(void *buf, size_t size)
{
    uint64_t block_type;

    block_type = *(uint64_t *)buf;

    if (block_type == ZBT_MICRO || block_type == BSWAP_64(ZBT_MICRO)) {
        /* ASSERT(magic == ZAP_LEAF_MAGIC); */
        mzap_byteswap(buf, size);
    } else {
        fzap_byteswap(buf, size);
    }
}

static int
mze_compare(const void *arg1, const void *arg2)
{
    const mzap_ent_t *mze1 = arg1;
    const mzap_ent_t *mze2 = arg2;

    if (mze1->mze_hash > mze2->mze_hash)
        return (+1);
    if (mze1->mze_hash < mze2->mze_hash)
        return (-1);
    if (mze1->mze_phys.mze_cd > mze2->mze_phys.mze_cd)
        return (+1);
    if (mze1->mze_phys.mze_cd < mze2->mze_phys.mze_cd)
        return (-1);
    return (0);
}

static void
mze_insert(zap_t *zap, int chunkid, uint64_t hash, mzap_ent_phys_t *mzep)
{
    mzap_ent_t *mze;

    ASSERT(zap->zap_ismicro);
    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    ASSERT(mzep->mze_cd < ZAP_MAXCD);

    mze = kmem_alloc(sizeof (mzap_ent_t), KM_SLEEP);
    mze->mze_chunkid = chunkid;
    mze->mze_hash = hash;
    mze->mze_phys = *mzep;
    avl_add(&zap->zap_m.zap_avl, mze);
}

static mzap_ent_t *
mze_find(zap_name_t *zn)
{
    mzap_ent_t mze_tofind;
    mzap_ent_t *mze;
    avl_index_t idx;
    avl_tree_t *avl = &zn->zn_zap->zap_m.zap_avl;

    ASSERT(zn->zn_zap->zap_ismicro);
    ASSERT(RW_LOCK_HELD(&zn->zn_zap->zap_rwlock));

    if (strlen(zn->zn_name_norm) >= sizeof (mze_tofind.mze_phys.mze_name))
        return (NULL);

    mze_tofind.mze_hash = zn->zn_hash;
    mze_tofind.mze_phys.mze_cd = 0;

again:
    mze = avl_find(avl, &mze_tofind, &idx);
    if (mze == NULL)
        mze = avl_nearest(avl, idx, AVL_AFTER);
    for (; mze && mze->mze_hash == zn->zn_hash; mze = AVL_NEXT(avl, mze)) {
        if (zap_match(zn, mze->mze_phys.mze_name))
            return (mze);
    }
    if (zn->zn_matchtype == MT_BEST) {
        zn->zn_matchtype = MT_FIRST;
        goto again;
    }
    return (NULL);
}

static uint32_t
mze_find_unused_cd(zap_t *zap, uint64_t hash)
{
    mzap_ent_t mze_tofind;
    mzap_ent_t *mze;
    avl_index_t idx;
    avl_tree_t *avl = &zap->zap_m.zap_avl;
    uint32_t cd;

    ASSERT(zap->zap_ismicro);
    ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));

    mze_tofind.mze_hash = hash;
    mze_tofind.mze_phys.mze_cd = 0;

    cd = 0;
    for (mze = avl_find(avl, &mze_tofind, &idx);
        mze && mze->mze_hash == hash; mze = AVL_NEXT(avl, mze)) {
        if (mze->mze_phys.mze_cd != cd)
            break;
        cd++;
    }

    return (cd);
}

static void
mze_remove(zap_t *zap, mzap_ent_t *mze)
{
    ASSERT(zap->zap_ismicro);
    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));

    avl_remove(&zap->zap_m.zap_avl, mze);
    kmem_free(mze, sizeof (mzap_ent_t));
}

static void
mze_destroy(zap_t *zap)
{
    mzap_ent_t *mze;
    void *avlcookie = NULL;

    while (mze = avl_destroy_nodes(&zap->zap_m.zap_avl, &avlcookie))
        kmem_free(mze, sizeof (mzap_ent_t));
    avl_destroy(&zap->zap_m.zap_avl);
}

static zap_t *
mzap_open(objset_t *os, uint64_t obj, dmu_buf_t *db)
{
    zap_t *winner;
    zap_t *zap;
    int i;

    ASSERT3U(MZAP_ENT_LEN, ==, sizeof (mzap_ent_phys_t));

    zap = kmem_zalloc(sizeof (zap_t), KM_SLEEP);
    rw_init(&zap->zap_rwlock, 0, 0, 0);
    rw_enter(&zap->zap_rwlock, RW_WRITER);
    zap->zap_objset = os;
    zap->zap_object = obj;
    zap->zap_dbuf = db;

    if (*(uint64_t *)db->db_data != ZBT_MICRO) {
        mutex_init(&zap->zap_f.zap_num_entries_mtx, 0, 0, 0);
        zap->zap_f.zap_block_shift = highbit(db->db_size) - 1;
    } else {
        zap->zap_ismicro = TRUE;
    }

    /*
     * Make sure that zap_ismicro is set before we let others see
     * it, because zap_lockdir() checks zap_ismicro without the lock
     * held.
     */
    winner = dmu_buf_set_user(db, zap, &zap->zap_m.zap_phys, zap_evict);

    if (winner != NULL) {
        rw_exit(&zap->zap_rwlock);
        rw_destroy(&zap->zap_rwlock);
        if (!zap->zap_ismicro)
            mutex_destroy(&zap->zap_f.zap_num_entries_mtx);
        kmem_free(zap, sizeof (zap_t));
        return (winner);
    }

    if (zap->zap_ismicro) {
        zap->zap_salt = zap->zap_m.zap_phys->mz_salt;
        zap->zap_normflags = zap->zap_m.zap_phys->mz_normflags;
        zap->zap_m.zap_num_chunks = db->db_size / MZAP_ENT_LEN - 1;
        avl_create(&zap->zap_m.zap_avl, mze_compare,
            sizeof (mzap_ent_t), offsetof(mzap_ent_t, mze_node));

        for (i = 0; i < zap->zap_m.zap_num_chunks; i++) {
            mzap_ent_phys_t *mze =
                &zap->zap_m.zap_phys->mz_chunk[i];
            if (mze->mze_name[0]) {
                zap_name_t *zn;

                zap->zap_m.zap_num_entries++;
                zn = zap_name_alloc(zap, mze->mze_name,
                    MT_EXACT);
                mze_insert(zap, i, zn->zn_hash, mze);
                zap_name_free(zn);
            }
        }
    } else {
        zap->zap_salt = zap->zap_f.zap_phys->zap_salt;
        zap->zap_normflags = zap->zap_f.zap_phys->zap_normflags;

        ASSERT3U(sizeof (struct zap_leaf_header), ==,
            2*ZAP_LEAF_CHUNKSIZE);

        /*
         * The embedded pointer table should not overlap the
         * other members.
         */
        ASSERT3P(&ZAP_EMBEDDED_PTRTBL_ENT(zap, 0), >,
            &zap->zap_f.zap_phys->zap_salt);

        /*
         * The embedded pointer table should end at the end of
         * the block
         */
        ASSERT3U((uintptr_t)&ZAP_EMBEDDED_PTRTBL_ENT(zap,
            1<<ZAP_EMBEDDED_PTRTBL_SHIFT(zap)) -
            (uintptr_t)zap->zap_f.zap_phys, ==,
            zap->zap_dbuf->db_size);
    }
    rw_exit(&zap->zap_rwlock);
    return (zap);
}

int
zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
    krw_t lti, boolean_t fatreader, boolean_t adding, zap_t **zapp)
{
    zap_t *zap;
    dmu_buf_t *db;
    krw_t lt;
    int err;

    *zapp = NULL;

    err = dmu_buf_hold(os, obj, 0, NULL, &db);
    if (err)
        return (err);

#ifdef ZFS_DEBUG
    {
        dmu_object_info_t doi;
        dmu_object_info_from_db(db, &doi);
        ASSERT(dmu_ot[doi.doi_type].ot_byteswap == zap_byteswap);
    }
#endif

    zap = dmu_buf_get_user(db);
    if (zap == NULL)
        zap = mzap_open(os, obj, db);

    /*
     * We're checking zap_ismicro without the lock held, in order to
     * tell what type of lock we want.  Once we have some sort of
     * lock, see if it really is the right type.  In practice this
     * can only be different if it was upgraded from micro to fat,
     * and micro wanted WRITER but fat only needs READER.
     */
    lt = (!zap->zap_ismicro && fatreader) ? RW_READER : lti;
    rw_enter(&zap->zap_rwlock, lt);
    if (lt != ((!zap->zap_ismicro && fatreader) ? RW_READER : lti)) {
        /* it was upgraded, now we only need reader */
        ASSERT(lt == RW_WRITER);
        ASSERT(RW_READER ==
            (!zap->zap_ismicro && fatreader) ? RW_READER : lti);
        rw_downgrade(&zap->zap_rwlock);
        lt = RW_READER;
    }

    zap->zap_objset = os;

    if (lt == RW_WRITER)
        dmu_buf_will_dirty(db, tx);

    ASSERT3P(zap->zap_dbuf, ==, db);

    ASSERT(!zap->zap_ismicro ||
        zap->zap_m.zap_num_entries <= zap->zap_m.zap_num_chunks);
    if (zap->zap_ismicro && tx && adding &&
        zap->zap_m.zap_num_entries == zap->zap_m.zap_num_chunks) {
        uint64_t newsz = db->db_size + SPA_MINBLOCKSIZE;
        if (newsz > MZAP_MAX_BLKSZ) {
            dprintf("upgrading obj %llu: num_entries=%u\n",
                obj, zap->zap_m.zap_num_entries);
            mzap_upgrade(zap, tx);
            *zapp = zap;
            return (0);
        }
        err = dmu_object_set_blocksize(os, obj, newsz, 0, tx);
        ASSERT3U(err, ==, 0);
        zap->zap_m.zap_num_chunks =
            db->db_size / MZAP_ENT_LEN - 1;
    }

    *zapp = zap;
    return (0);
}

void
zap_unlockdir(zap_t *zap)
{
    rw_exit(&zap->zap_rwlock);
    dmu_buf_rele(zap->zap_dbuf, NULL);
}

static void
mzap_upgrade(zap_t *zap, dmu_tx_t *tx)
{
    mzap_phys_t *mzp;
    int i, sz, nchunks, err;

    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));

    sz = zap->zap_dbuf->db_size;
    mzp = kmem_alloc(sz, KM_SLEEP);
    bcopy(zap->zap_dbuf->db_data, mzp, sz);
    nchunks = zap->zap_m.zap_num_chunks;

    err = dmu_object_set_blocksize(zap->zap_objset, zap->zap_object,
        1ULL << fzap_default_block_shift, 0, tx);
    ASSERT(err == 0);

    dprintf("upgrading obj=%llu with %u chunks\n",
        zap->zap_object, nchunks);
    /* XXX destroy the avl later, so we can use the stored hash value */
    mze_destroy(zap);

    fzap_upgrade(zap, tx);

    for (i = 0; i < nchunks; i++) {
        int err;
        mzap_ent_phys_t *mze = &mzp->mz_chunk[i];
        zap_name_t *zn;
        if (mze->mze_name[0] == 0)
            continue;
        dprintf("adding %s=%llu\n",
            mze->mze_name, mze->mze_value);
        zn = zap_name_alloc(zap, mze->mze_name, MT_EXACT);
        err = fzap_add_cd(zn, 8, 1, &mze->mze_value,
            mze->mze_cd, tx);
        zap_name_free(zn);
        ASSERT3U(err, ==, 0);
    }
    kmem_free(mzp, sz);
}

static void
mzap_create_impl(objset_t *os, uint64_t obj, int normflags, dmu_tx_t *tx)
{
    dmu_buf_t *db;
    mzap_phys_t *zp;

    ASSERT(normflags == 0 ||
        spa_version(dmu_objset_spa(os)) >= SPA_VERSION_NORMALIZATION);
    VERIFY(0 == dmu_buf_hold(os, obj, 0, FTAG, &db));

#ifdef ZFS_DEBUG
    {
        dmu_object_info_t doi;
        dmu_object_info_from_db(db, &doi);
        ASSERT(dmu_ot[doi.doi_type].ot_byteswap == zap_byteswap);
    }
#endif

    dmu_buf_will_dirty(db, tx);
    zp = db->db_data;
    zp->mz_block_type = ZBT_MICRO;
    zp->mz_salt = ((uintptr_t)db ^ (uintptr_t)tx ^ (obj << 1)) | 1ULL;
    zp->mz_normflags = normflags;
    dmu_buf_rele(db, FTAG);
}

int
zap_create_claim(objset_t *os, uint64_t obj, dmu_object_type_t ot,
    dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
{
    return (zap_create_claim_norm(os, obj,
        0, ot, bonustype, bonuslen, tx));
}

int
zap_create_claim_norm(objset_t *os, uint64_t obj, int normflags,
    dmu_object_type_t ot,
    dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
{
    int err;

    err = dmu_object_claim(os, obj, ot, 0, bonustype, bonuslen, tx);
    if (err != 0)
        return (err);
    mzap_create_impl(os, obj, normflags, tx);
    return (0);
}

uint64_t
zap_create(objset_t *os, dmu_object_type_t ot,
    dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
{
    return (zap_create_norm(os, 0, ot, bonustype, bonuslen, tx));
}

uint64_t
zap_create_norm(objset_t *os, int normflags, dmu_object_type_t ot,
    dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
{
    uint64_t obj = dmu_object_alloc(os, ot, 0, bonustype, bonuslen, tx);

    mzap_create_impl(os, obj, normflags, tx);
    return (obj);
}

int
zap_destroy(objset_t *os, uint64_t zapobj, dmu_tx_t *tx)
{
    /*
     * dmu_object_free will free the object number and free the
     * data.  Freeing the data will cause our pageout function to be
     * called, which will destroy our data (zap_leaf_t's and zap_t).
     */

    return (dmu_object_free(os, zapobj, tx));
}

_NOTE(ARGSUSED(0))
void
zap_evict(dmu_buf_t *db, void *vzap)
{
    zap_t *zap = vzap;

    rw_destroy(&zap->zap_rwlock);

    if (zap->zap_ismicro)
        mze_destroy(zap);
    else
        mutex_destroy(&zap->zap_f.zap_num_entries_mtx);

    kmem_free(zap, sizeof (zap_t));
}

int
zap_count(objset_t *os, uint64_t zapobj, uint64_t *count)
{
    zap_t *zap;
    int err;

    err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
    if (err)
        return (err);
    if (!zap->zap_ismicro) {
        err = fzap_count(zap, count);
    } else {
        *count = zap->zap_m.zap_num_entries;
    }
    zap_unlockdir(zap);
    return (err);
}

/*
 * zn may be NULL; if not specified, it will be computed if needed.
 * See also the comment above zap_entry_normalization_conflict().
 */
static boolean_t
mzap_normalization_conflict(zap_t *zap, zap_name_t *zn, mzap_ent_t *mze)
{
    mzap_ent_t *other;
    int direction = AVL_BEFORE;
    boolean_t allocdzn = B_FALSE;

    if (zap->zap_normflags == 0)
        return (B_FALSE);

again:
    for (other = avl_walk(&zap->zap_m.zap_avl, mze, direction);
        other && other->mze_hash == mze->mze_hash;
        other = avl_walk(&zap->zap_m.zap_avl, other, direction)) {

        if (zn == NULL) {
            zn = zap_name_alloc(zap, mze->mze_phys.mze_name,
                MT_FIRST);
            allocdzn = B_TRUE;
        }
        if (zap_match(zn, other->mze_phys.mze_name)) {
            if (allocdzn)
                zap_name_free(zn);
            return (B_TRUE);
        }
    }

    if (direction == AVL_BEFORE) {
        direction = AVL_AFTER;
        goto again;
    }

    if (allocdzn)
        zap_name_free(zn);
    return (B_FALSE);
}

/*
 * Routines for manipulating attributes.
 */

int
zap_lookup(objset_t *os, uint64_t zapobj, const char *name,
    uint64_t integer_size, uint64_t num_integers, void *buf)
{
    return (zap_lookup_norm(os, zapobj, name, integer_size,
        num_integers, buf, MT_EXACT, NULL, 0, NULL));
}

int
zap_lookup_norm(objset_t *os, uint64_t zapobj, const char *name,
    uint64_t integer_size, uint64_t num_integers, void *buf,
    matchtype_t mt, char *realname, int rn_len,
    boolean_t *ncp)
{
    zap_t *zap;
    int err;
    mzap_ent_t *mze;
    zap_name_t *zn;

    err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
    if (err)
        return (err);
    zn = zap_name_alloc(zap, name, mt);
    if (zn == NULL) {
        zap_unlockdir(zap);
        return (ENOTSUP);
    }

    if (!zap->zap_ismicro) {
        err = fzap_lookup(zn, integer_size, num_integers, buf,
            realname, rn_len, ncp);
    } else {
        mze = mze_find(zn);
        if (mze == NULL) {
            err = ENOENT;
        } else {
            if (num_integers < 1) {
                err = EOVERFLOW;
            } else if (integer_size != 8) {
                err = EINVAL;
            } else {
                *(uint64_t *)buf = mze->mze_phys.mze_value;
                (void) strlcpy(realname,
                    mze->mze_phys.mze_name, rn_len);
                if (ncp) {
                    *ncp = mzap_normalization_conflict(zap,
                        zn, mze);
                }
            }
        }
    }
    zap_name_free(zn);
    zap_unlockdir(zap);
    return (err);
}

int
zap_length(objset_t *os, uint64_t zapobj, const char *name,
    uint64_t *integer_size, uint64_t *num_integers)
{
    zap_t *zap;
    int err;
    mzap_ent_t *mze;
    zap_name_t *zn;

    err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
    if (err)
        return (err);
    zn = zap_name_alloc(zap, name, MT_EXACT);
    if (zn == NULL) {
        zap_unlockdir(zap);
        return (ENOTSUP);
    }
    if (!zap->zap_ismicro) {
        err = fzap_length(zn, integer_size, num_integers);
    } else {
        mze = mze_find(zn);
        if (mze == NULL) {
            err = ENOENT;
        } else {
            if (integer_size)
                *integer_size = 8;
            if (num_integers)
                *num_integers = 1;
        }
    }
    zap_name_free(zn);
    zap_unlockdir(zap);
    return (err);
}

static void
mzap_addent(zap_name_t *zn, uint64_t value)
{
    int i;
    zap_t *zap = zn->zn_zap;
    int start = zap->zap_m.zap_alloc_next;
    uint32_t cd;

    dprintf("obj=%llu %s=%llu\n", zap->zap_object,
        zn->zn_name_orij, value);
    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));

#ifdef ZFS_DEBUG
    for (i = 0; i < zap->zap_m.zap_num_chunks; i++) {
        mzap_ent_phys_t *mze = &zap->zap_m.zap_phys->mz_chunk[i];
        ASSERT(strcmp(zn->zn_name_orij, mze->mze_name) != 0);
    }
#endif

    cd = mze_find_unused_cd(zap, zn->zn_hash);
    /* given the limited size of the microzap, this can't happen */
    ASSERT(cd != ZAP_MAXCD);

again:
    for (i = start; i < zap->zap_m.zap_num_chunks; i++) {
        mzap_ent_phys_t *mze = &zap->zap_m.zap_phys->mz_chunk[i];
        if (mze->mze_name[0] == 0) {
            mze->mze_value = value;
            mze->mze_cd = cd;
            (void) strcpy(mze->mze_name, zn->zn_name_orij);
            zap->zap_m.zap_num_entries++;
            zap->zap_m.zap_alloc_next = i+1;
            if (zap->zap_m.zap_alloc_next ==
                zap->zap_m.zap_num_chunks)
                zap->zap_m.zap_alloc_next = 0;
            mze_insert(zap, i, zn->zn_hash, mze);
            return;
        }
    }
    if (start != 0) {
        start = 0;
        goto again;
    }
    ASSERT(!"out of entries!");
}

int
zap_add(objset_t *os, uint64_t zapobj, const char *name,
    int integer_size, uint64_t num_integers,
    const void *val, dmu_tx_t *tx)
{
    zap_t *zap;
    int err;
    mzap_ent_t *mze;
    const uint64_t *intval = val;
    zap_name_t *zn;

    err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, &zap);
    if (err)
        return (err);
    zn = zap_name_alloc(zap, name, MT_EXACT);
    if (zn == NULL) {
        zap_unlockdir(zap);
        return (ENOTSUP);
    }
    if (!zap->zap_ismicro) {
        err = fzap_add(zn, integer_size, num_integers, val, tx);
    } else if (integer_size != 8 || num_integers != 1 ||
        strlen(name) >= MZAP_NAME_LEN) {
        dprintf("upgrading obj %llu: intsz=%u numint=%llu name=%s\n",
            zapobj, integer_size, num_integers, name);
        mzap_upgrade(zap, tx);
        err = fzap_add(zn, integer_size, num_integers, val, tx);
    } else {
        mze = mze_find(zn);
        if (mze != NULL) {
            err = EEXIST;
        } else {
            mzap_addent(zn, *intval);
        }
    }
    zap_name_free(zn);
    zap_unlockdir(zap);
    return (err);
}

int
zap_update(objset_t *os, uint64_t zapobj, const char *name,
    int integer_size, uint64_t num_integers, const void *val, dmu_tx_t *tx)
{
    zap_t *zap;
    mzap_ent_t *mze;
    const uint64_t *intval = val;
    zap_name_t *zn;
    int err;

    err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, &zap);
    if (err)
        return (err);
    zn = zap_name_alloc(zap, name, MT_EXACT);
    if (zn == NULL) {
        zap_unlockdir(zap);
        return (ENOTSUP);
    }
    if (!zap->zap_ismicro) {
        err = fzap_update(zn, integer_size, num_integers, val, tx);
    } else if (integer_size != 8 || num_integers != 1 ||
        strlen(name) >= MZAP_NAME_LEN) {
        dprintf("upgrading obj %llu: intsz=%u numint=%llu name=%s\n",
            zapobj, integer_size, num_integers, name);
        mzap_upgrade(zap, tx);
        err = fzap_update(zn, integer_size, num_integers, val, tx);
    } else {
        mze = mze_find(zn);
        if (mze != NULL) {
            mze->mze_phys.mze_value = *intval;
            zap->zap_m.zap_phys->mz_chunk
                [mze->mze_chunkid].mze_value = *intval;
        } else {
            mzap_addent(zn, *intval);
        }
    }
    zap_name_free(zn);
    zap_unlockdir(zap);
    return (err);
}

int
zap_remove(objset_t *os, uint64_t zapobj, const char *name, dmu_tx_t *tx)
{
    return (zap_remove_norm(os, zapobj, name, MT_EXACT, tx));
}

int
zap_remove_norm(objset_t *os, uint64_t zapobj, const char *name,
    matchtype_t mt, dmu_tx_t *tx)
{
    zap_t *zap;
    int err;
    mzap_ent_t *mze;
    zap_name_t *zn;

    err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, FALSE, &zap);
    if (err)
        return (err);
    zn = zap_name_alloc(zap, name, mt);
    if (zn == NULL) {
        zap_unlockdir(zap);
        return (ENOTSUP);
    }
    if (!zap->zap_ismicro) {
        err = fzap_remove(zn, tx);
    } else {
        mze = mze_find(zn);
        if (mze == NULL) {
            err = ENOENT;
        } else {
            zap->zap_m.zap_num_entries--;
            bzero(&zap->zap_m.zap_phys->mz_chunk[mze->mze_chunkid],
                sizeof (mzap_ent_phys_t));
            mze_remove(zap, mze);
        }
    }
    zap_name_free(zn);
    zap_unlockdir(zap);
    return (err);
}

/*
 * Routines for iterating over the attributes.
 */

/*
 * We want to keep the high 32 bits of the cursor zero if we can, so
 * that 32-bit programs can access this.  So use a small hash value so
 * we can fit 4 bits of cd into the 32-bit cursor.
 *
 * [ 4 zero bits | 32-bit collision differentiator | 28-bit hash value ]
 */
void
zap_cursor_init_serialized(zap_cursor_t *zc, objset_t *os, uint64_t zapobj,
    uint64_t serialized)
{
    zc->zc_objset = os;
    zc->zc_zap = NULL;
    zc->zc_leaf = NULL;
    zc->zc_zapobj = zapobj;
    if (serialized == -1ULL) {
        zc->zc_hash = -1ULL;
        zc->zc_cd = 0;
    } else {
        zc->zc_hash = serialized << (64-ZAP_HASHBITS);
        zc->zc_cd = serialized >> ZAP_HASHBITS;
        if (zc->zc_cd >= ZAP_MAXCD) /* corrupt serialized */
            zc->zc_cd = 0;
    }
}

void
zap_cursor_init(zap_cursor_t *zc, objset_t *os, uint64_t zapobj)
{
    zap_cursor_init_serialized(zc, os, zapobj, 0);
}

void
zap_cursor_fini(zap_cursor_t *zc)
{
    if (zc->zc_zap) {
        rw_enter(&zc->zc_zap->zap_rwlock, RW_READER);
        zap_unlockdir(zc->zc_zap);
        zc->zc_zap = NULL;
    }
    if (zc->zc_leaf) {
        rw_enter(&zc->zc_leaf->l_rwlock, RW_READER);
        zap_put_leaf(zc->zc_leaf);
        zc->zc_leaf = NULL;
    }
    zc->zc_objset = NULL;
}

uint64_t
zap_cursor_serialize(zap_cursor_t *zc)
{
    if (zc->zc_hash == -1ULL)
        return (-1ULL);
    ASSERT((zc->zc_hash & (ZAP_MAXCD-1)) == 0);
    ASSERT(zc->zc_cd < ZAP_MAXCD);
    return ((zc->zc_hash >> (64-ZAP_HASHBITS)) |
        ((uint64_t)zc->zc_cd << ZAP_HASHBITS));
}

int
zap_cursor_retrieve(zap_cursor_t *zc, zap_attribute_t *za)
{
    int err;
    avl_index_t idx;
    mzap_ent_t mze_tofind;
    mzap_ent_t *mze;

    if (zc->zc_hash == -1ULL)
        return (ENOENT);

    if (zc->zc_zap == NULL) {
        err = zap_lockdir(zc->zc_objset, zc->zc_zapobj, NULL,
            RW_READER, TRUE, FALSE, &zc->zc_zap);
        if (err)
            return (err);
    } else {
        rw_enter(&zc->zc_zap->zap_rwlock, RW_READER);
    }
    if (!zc->zc_zap->zap_ismicro) {
        err = fzap_cursor_retrieve(zc->zc_zap, zc, za);
    } else {
        err = ENOENT;

        mze_tofind.mze_hash = zc->zc_hash;
        mze_tofind.mze_phys.mze_cd = zc->zc_cd;

        mze = avl_find(&zc->zc_zap->zap_m.zap_avl, &mze_tofind, &idx);
        if (mze == NULL) {
            mze = avl_nearest(&zc->zc_zap->zap_m.zap_avl,
                idx, AVL_AFTER);
        }
        if (mze) {
            ASSERT(0 == bcmp(&mze->mze_phys,
                &zc->zc_zap->zap_m.zap_phys->mz_chunk
                [mze->mze_chunkid], sizeof (mze->mze_phys)));

            za->za_normalization_conflict =
                mzap_normalization_conflict(zc->zc_zap, NULL, mze);
            za->za_integer_length = 8;
            za->za_num_integers = 1;
            za->za_first_integer = mze->mze_phys.mze_value;
            (void) strcpy(za->za_name, mze->mze_phys.mze_name);
            zc->zc_hash = mze->mze_hash;
            zc->zc_cd = mze->mze_phys.mze_cd;
            err = 0;
        } else {
            zc->zc_hash = -1ULL;
        }
    }
    rw_exit(&zc->zc_zap->zap_rwlock);
    return (err);
}

void
zap_cursor_advance(zap_cursor_t *zc)
{
    if (zc->zc_hash == -1ULL)
        return;
    zc->zc_cd++;
    if (zc->zc_cd >= ZAP_MAXCD) {
        zc->zc_cd = 0;
        zc->zc_hash += 1ULL<<(64-ZAP_HASHBITS);
        if (zc->zc_hash == 0) /* EOF */
            zc->zc_hash = -1ULL;
    }
}

int
zap_get_stats(objset_t *os, uint64_t zapobj, zap_stats_t *zs)
{
    int err;
    zap_t *zap;

    err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
    if (err)
        return (err);

    bzero(zs, sizeof (zap_stats_t));

    if (zap->zap_ismicro) {
        zs->zs_blocksize = zap->zap_dbuf->db_size;
        zs->zs_num_entries = zap->zap_m.zap_num_entries;
        zs->zs_num_blocks = 1;
    } else {
        fzap_get_stats(zap, zs);
    }
    zap_unlockdir(zap);
    return (0);
}