fs/zfs/zap.c

	zap.c revision ad860c82b2a8ffe69f42630da73ded0c92a7a36e
/*
 * 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"


/*
 * This file contains the top half of the zfs directory structure
 * implementation. The bottom half is in zap_leaf.c.
 *
 * The zdir is an extendable hash data structure. There is a table of
 * pointers to buckets (zap_t->zd_data->zd_leafs). The buckets are
 * each a constant size and hold a variable number of directory entries.
 * The buckets (aka "leaf nodes") are implemented in zap_leaf.c.
 *
 * The pointer table holds a power of 2 number of pointers.
 * (1<<zap_t->zd_data->zd_phys->zd_prefix_len).  The bucket pointed to
 * by the pointer at index i in the table holds entries whose hash value
 * has a zd_prefix_len - bit prefix
 */

#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>

int fzap_default_block_shift = 14; /* 16k blocksize */

static void zap_leaf_pageout(dmu_buf_t *db, void *vl);
static uint64_t zap_allocate_blocks(zap_t *zap, int nblocks);


void
fzap_byteswap(void *vbuf, size_t size)
{
    uint64_t block_type;

    block_type = *(uint64_t *)vbuf;

    if (block_type == ZBT_LEAF || block_type == BSWAP_64(ZBT_LEAF))
        zap_leaf_byteswap(vbuf, size);
    else {
        /* it's a ptrtbl block */
        byteswap_uint64_array(vbuf, size);
    }
}

void
fzap_upgrade(zap_t *zap, dmu_tx_t *tx)
{
    dmu_buf_t *db;
    zap_leaf_t *l;
    int i;
    zap_phys_t *zp;

    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    zap->zap_ismicro = FALSE;

    (void) dmu_buf_update_user(zap->zap_dbuf, zap, zap,
        &zap->zap_f.zap_phys, zap_evict);

    mutex_init(&zap->zap_f.zap_num_entries_mtx, 0, 0, 0);
    zap->zap_f.zap_block_shift = highbit(zap->zap_dbuf->db_size) - 1;

    zp = zap->zap_f.zap_phys;
    /*
     * explicitly zero it since it might be coming from an
     * initialized microzap
     */
    bzero(zap->zap_dbuf->db_data, zap->zap_dbuf->db_size);
    zp->zap_block_type = ZBT_HEADER;
    zp->zap_magic = ZAP_MAGIC;

    zp->zap_ptrtbl.zt_shift = ZAP_EMBEDDED_PTRTBL_SHIFT(zap);

    zp->zap_freeblk = 2;        /* block 1 will be the first leaf */
    zp->zap_num_leafs = 1;
    zp->zap_num_entries = 0;
    zp->zap_salt = zap->zap_salt;
    zp->zap_normflags = zap->zap_normflags;

    /* block 1 will be the first leaf */
    for (i = 0; i < (1<<zp->zap_ptrtbl.zt_shift); i++)
        ZAP_EMBEDDED_PTRTBL_ENT(zap, i) = 1;

    /*
     * set up block 1 - the first leaf
     */
    VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
        1<<FZAP_BLOCK_SHIFT(zap), FTAG, &db));
    dmu_buf_will_dirty(db, tx);

    l = kmem_zalloc(sizeof (zap_leaf_t), KM_SLEEP);
    l->l_dbuf = db;
    l->l_phys = db->db_data;

    zap_leaf_init(l, spa_version(dmu_objset_spa(zap->zap_objset)));

    kmem_free(l, sizeof (zap_leaf_t));
    dmu_buf_rele(db, FTAG);
}

static int
zap_tryupgradedir(zap_t *zap, dmu_tx_t *tx)
{
    if (RW_WRITE_HELD(&zap->zap_rwlock))
        return (1);
    if (rw_tryupgrade(&zap->zap_rwlock)) {
        dmu_buf_will_dirty(zap->zap_dbuf, tx);
        return (1);
    }
    return (0);
}

/*
 * Generic routines for dealing with the pointer & cookie tables.
 */

static int
zap_table_grow(zap_t *zap, zap_table_phys_t *tbl,
    void (*transfer_func)(const uint64_t *src, uint64_t *dst, int n),
    dmu_tx_t *tx)
{
    uint64_t b, newblk;
    dmu_buf_t *db_old, *db_new;
    int err;
    int bs = FZAP_BLOCK_SHIFT(zap);
    int hepb = 1<<(bs-4);
    /* hepb = half the number of entries in a block */

    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    ASSERT(tbl->zt_blk != 0);
    ASSERT(tbl->zt_numblks > 0);

    if (tbl->zt_nextblk != 0) {
        newblk = tbl->zt_nextblk;
    } else {
        newblk = zap_allocate_blocks(zap, tbl->zt_numblks * 2);
        tbl->zt_nextblk = newblk;
        ASSERT3U(tbl->zt_blks_copied, ==, 0);
        dmu_prefetch(zap->zap_objset, zap->zap_object,
            tbl->zt_blk << bs, tbl->zt_numblks << bs);
    }

    /*
     * Copy the ptrtbl from the old to new location.
     */

    b = tbl->zt_blks_copied;
    err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
        (tbl->zt_blk + b) << bs, FTAG, &db_old);
    if (err)
        return (err);

    /* first half of entries in old[b] go to new[2*b+0] */
    VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
        (newblk + 2*b+0) << bs, FTAG, &db_new));
    dmu_buf_will_dirty(db_new, tx);
    transfer_func(db_old->db_data, db_new->db_data, hepb);
    dmu_buf_rele(db_new, FTAG);

    /* second half of entries in old[b] go to new[2*b+1] */
    VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
        (newblk + 2*b+1) << bs, FTAG, &db_new));
    dmu_buf_will_dirty(db_new, tx);
    transfer_func((uint64_t *)db_old->db_data + hepb,
        db_new->db_data, hepb);
    dmu_buf_rele(db_new, FTAG);

    dmu_buf_rele(db_old, FTAG);

    tbl->zt_blks_copied++;

    dprintf("copied block %llu of %llu\n",
        tbl->zt_blks_copied, tbl->zt_numblks);

    if (tbl->zt_blks_copied == tbl->zt_numblks) {
        (void) dmu_free_range(zap->zap_objset, zap->zap_object,
            tbl->zt_blk << bs, tbl->zt_numblks << bs, tx);

        tbl->zt_blk = newblk;
        tbl->zt_numblks *= 2;
        tbl->zt_shift++;
        tbl->zt_nextblk = 0;
        tbl->zt_blks_copied = 0;

        dprintf("finished; numblocks now %llu (%lluk entries)\n",
            tbl->zt_numblks, 1<<(tbl->zt_shift-10));
    }

    return (0);
}

static int
zap_table_store(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t val,
    dmu_tx_t *tx)
{
    int err;
    uint64_t blk, off;
    int bs = FZAP_BLOCK_SHIFT(zap);
    dmu_buf_t *db;

    ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    ASSERT(tbl->zt_blk != 0);

    dprintf("storing %llx at index %llx\n", val, idx);

    blk = idx >> (bs-3);
    off = idx & ((1<<(bs-3))-1);

    err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
        (tbl->zt_blk + blk) << bs, FTAG, &db);
    if (err)
        return (err);
    dmu_buf_will_dirty(db, tx);

    if (tbl->zt_nextblk != 0) {
        uint64_t idx2 = idx * 2;
        uint64_t blk2 = idx2 >> (bs-3);
        uint64_t off2 = idx2 & ((1<<(bs-3))-1);
        dmu_buf_t *db2;

        err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
            (tbl->zt_nextblk + blk2) << bs, FTAG, &db2);
        if (err) {
            dmu_buf_rele(db, FTAG);
            return (err);
        }
        dmu_buf_will_dirty(db2, tx);
        ((uint64_t *)db2->db_data)[off2] = val;
        ((uint64_t *)db2->db_data)[off2+1] = val;
        dmu_buf_rele(db2, FTAG);
    }

    ((uint64_t *)db->db_data)[off] = val;
    dmu_buf_rele(db, FTAG);

    return (0);
}

static int
zap_table_load(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t *valp)
{
    uint64_t blk, off;
    int err;
    dmu_buf_t *db;
    int bs = FZAP_BLOCK_SHIFT(zap);

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

    blk = idx >> (bs-3);
    off = idx & ((1<<(bs-3))-1);

    err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
        (tbl->zt_blk + blk) << bs, FTAG, &db);
    if (err)
        return (err);
    *valp = ((uint64_t *)db->db_data)[off];
    dmu_buf_rele(db, FTAG);

    if (tbl->zt_nextblk != 0) {
        /*
         * read the nextblk for the sake of i/o error checking,
         * so that zap_table_load() will catch errors for
         * zap_table_store.
         */
        blk = (idx*2) >> (bs-3);

        err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
            (tbl->zt_nextblk + blk) << bs, FTAG, &db);
        dmu_buf_rele(db, FTAG);
    }
    return (err);
}

/*
 * Routines for growing the ptrtbl.
 */

static void
zap_ptrtbl_transfer(const uint64_t *src, uint64_t *dst, int n)
{
    int i;
    for (i = 0; i < n; i++) {
        uint64_t lb = src[i];
        dst[2*i+0] = lb;
        dst[2*i+1] = lb;
    }
}

static int
zap_grow_ptrtbl(zap_t *zap, dmu_tx_t *tx)
{
    /* In case things go horribly wrong. */
    if (zap->zap_f.zap_phys->zap_ptrtbl.zt_shift >= ZAP_HASHBITS-2)
        return (ENOSPC);

    if (zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks == 0) {
        /*
         * We are outgrowing the "embedded" ptrtbl (the one
         * stored in the header block).  Give it its own entire
         * block, which will double the size of the ptrtbl.
         */
        uint64_t newblk;
        dmu_buf_t *db_new;
        int err;

        ASSERT3U(zap->zap_f.zap_phys->zap_ptrtbl.zt_shift, ==,
            ZAP_EMBEDDED_PTRTBL_SHIFT(zap));
        ASSERT3U(zap->zap_f.zap_phys->zap_ptrtbl.zt_blk, ==, 0);

        newblk = zap_allocate_blocks(zap, 1);
        err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
            newblk << FZAP_BLOCK_SHIFT(zap), FTAG, &db_new);
        if (err)
            return (err);
        dmu_buf_will_dirty(db_new, tx);
        zap_ptrtbl_transfer(&ZAP_EMBEDDED_PTRTBL_ENT(zap, 0),
            db_new->db_data, 1 << ZAP_EMBEDDED_PTRTBL_SHIFT(zap));
        dmu_buf_rele(db_new, FTAG);

        zap->zap_f.zap_phys->zap_ptrtbl.zt_blk = newblk;
        zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks = 1;
        zap->zap_f.zap_phys->zap_ptrtbl.zt_shift++;

        ASSERT3U(1ULL << zap->zap_f.zap_phys->zap_ptrtbl.zt_shift, ==,
            zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks <<
            (FZAP_BLOCK_SHIFT(zap)-3));

        return (0);
    } else {
        return (zap_table_grow(zap, &zap->zap_f.zap_phys->zap_ptrtbl,
            zap_ptrtbl_transfer, tx));
    }
}

static void
zap_increment_num_entries(zap_t *zap, int delta, dmu_tx_t *tx)
{
    dmu_buf_will_dirty(zap->zap_dbuf, tx);
    mutex_enter(&zap->zap_f.zap_num_entries_mtx);
    ASSERT(delta > 0 || zap->zap_f.zap_phys->zap_num_entries >= -delta);
    zap->zap_f.zap_phys->zap_num_entries += delta;
    mutex_exit(&zap->zap_f.zap_num_entries_mtx);
}

static uint64_t
zap_allocate_blocks(zap_t *zap, int nblocks)
{
    uint64_t newblk;
    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    newblk = zap->zap_f.zap_phys->zap_freeblk;
    zap->zap_f.zap_phys->zap_freeblk += nblocks;
    return (newblk);
}

static zap_leaf_t *
zap_create_leaf(zap_t *zap, dmu_tx_t *tx)
{
    void *winner;
    zap_leaf_t *l = kmem_alloc(sizeof (zap_leaf_t), KM_SLEEP);

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

    rw_init(&l->l_rwlock, 0, 0, 0);
    rw_enter(&l->l_rwlock, RW_WRITER);
    l->l_blkid = zap_allocate_blocks(zap, 1);
    l->l_dbuf = NULL;
    l->l_phys = NULL;

    VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
        l->l_blkid << FZAP_BLOCK_SHIFT(zap), NULL, &l->l_dbuf));
    winner = dmu_buf_set_user(l->l_dbuf, l, &l->l_phys, zap_leaf_pageout);
    ASSERT(winner == NULL);
    dmu_buf_will_dirty(l->l_dbuf, tx);

    zap_leaf_init(l, spa_version(dmu_objset_spa(zap->zap_objset)));

    zap->zap_f.zap_phys->zap_num_leafs++;

    return (l);
}

int
fzap_count(zap_t *zap, uint64_t *count)
{
    ASSERT(!zap->zap_ismicro);
    mutex_enter(&zap->zap_f.zap_num_entries_mtx); /* unnecessary */
    *count = zap->zap_f.zap_phys->zap_num_entries;
    mutex_exit(&zap->zap_f.zap_num_entries_mtx);
    return (0);
}

/*
 * Routines for obtaining zap_leaf_t's
 */

void
zap_put_leaf(zap_leaf_t *l)
{
    rw_exit(&l->l_rwlock);
    dmu_buf_rele(l->l_dbuf, NULL);
}

_NOTE(ARGSUSED(0))
static void
zap_leaf_pageout(dmu_buf_t *db, void *vl)
{
    zap_leaf_t *l = vl;

    rw_destroy(&l->l_rwlock);
    kmem_free(l, sizeof (zap_leaf_t));
}

static zap_leaf_t *
zap_open_leaf(uint64_t blkid, dmu_buf_t *db)
{
    zap_leaf_t *l, *winner;

    ASSERT(blkid != 0);

    l = kmem_alloc(sizeof (zap_leaf_t), KM_SLEEP);
    rw_init(&l->l_rwlock, 0, 0, 0);
    rw_enter(&l->l_rwlock, RW_WRITER);
    l->l_blkid = blkid;
    l->l_bs = highbit(db->db_size)-1;
    l->l_dbuf = db;
    l->l_phys = NULL;

    winner = dmu_buf_set_user(db, l, &l->l_phys, zap_leaf_pageout);

    rw_exit(&l->l_rwlock);
    if (winner != NULL) {
        /* someone else set it first */
        zap_leaf_pageout(NULL, l);
        l = winner;
    }

    /*
     * lhr_pad was previously used for the next leaf in the leaf
     * chain.  There should be no chained leafs (as we have removed
     * support for them).
     */
    ASSERT3U(l->l_phys->l_hdr.lh_pad1, ==, 0);

    /*
     * There should be more hash entries than there can be
     * chunks to put in the hash table
     */
    ASSERT3U(ZAP_LEAF_HASH_NUMENTRIES(l), >, ZAP_LEAF_NUMCHUNKS(l) / 3);

    /* The chunks should begin at the end of the hash table */
    ASSERT3P(&ZAP_LEAF_CHUNK(l, 0), ==,
        &l->l_phys->l_hash[ZAP_LEAF_HASH_NUMENTRIES(l)]);

    /* The chunks should end at the end of the block */
    ASSERT3U((uintptr_t)&ZAP_LEAF_CHUNK(l, ZAP_LEAF_NUMCHUNKS(l)) -
        (uintptr_t)l->l_phys, ==, l->l_dbuf->db_size);

    return (l);
}

static int
zap_get_leaf_byblk(zap_t *zap, uint64_t blkid, dmu_tx_t *tx, krw_t lt,
    zap_leaf_t **lp)
{
    dmu_buf_t *db;
    zap_leaf_t *l;
    int bs = FZAP_BLOCK_SHIFT(zap);
    int err;

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

    err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
        blkid << bs, NULL, &db);
    if (err)
        return (err);

    ASSERT3U(db->db_object, ==, zap->zap_object);
    ASSERT3U(db->db_offset, ==, blkid << bs);
    ASSERT3U(db->db_size, ==, 1 << bs);
    ASSERT(blkid != 0);

    l = dmu_buf_get_user(db);

    if (l == NULL)
        l = zap_open_leaf(blkid, db);

    rw_enter(&l->l_rwlock, lt);
    /*
     * Must lock before dirtying, otherwise l->l_phys could change,
     * causing ASSERT below to fail.
     */
    if (lt == RW_WRITER)
        dmu_buf_will_dirty(db, tx);
    ASSERT3U(l->l_blkid, ==, blkid);
    ASSERT3P(l->l_dbuf, ==, db);
    ASSERT3P(l->l_phys, ==, l->l_dbuf->db_data);
    ASSERT3U(l->l_phys->l_hdr.lh_block_type, ==, ZBT_LEAF);
    ASSERT3U(l->l_phys->l_hdr.lh_magic, ==, ZAP_LEAF_MAGIC);

    *lp = l;
    return (0);
}

static int
zap_idx_to_blk(zap_t *zap, uint64_t idx, uint64_t *valp)
{
    ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));

    if (zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks == 0) {
        ASSERT3U(idx, <,
            (1ULL << zap->zap_f.zap_phys->zap_ptrtbl.zt_shift));
        *valp = ZAP_EMBEDDED_PTRTBL_ENT(zap, idx);
        return (0);
    } else {
        return (zap_table_load(zap, &zap->zap_f.zap_phys->zap_ptrtbl,
            idx, valp));
    }
}

static int
zap_set_idx_to_blk(zap_t *zap, uint64_t idx, uint64_t blk, dmu_tx_t *tx)
{
    ASSERT(tx != NULL);
    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));

    if (zap->zap_f.zap_phys->zap_ptrtbl.zt_blk == 0) {
        ZAP_EMBEDDED_PTRTBL_ENT(zap, idx) = blk;
        return (0);
    } else {
        return (zap_table_store(zap, &zap->zap_f.zap_phys->zap_ptrtbl,
            idx, blk, tx));
    }
}

static int
zap_deref_leaf(zap_t *zap, uint64_t h, dmu_tx_t *tx, krw_t lt, zap_leaf_t **lp)
{
    uint64_t idx, blk;
    int err;

    ASSERT(zap->zap_dbuf == NULL ||
        zap->zap_f.zap_phys == zap->zap_dbuf->db_data);
    ASSERT3U(zap->zap_f.zap_phys->zap_magic, ==, ZAP_MAGIC);
    idx = ZAP_HASH_IDX(h, zap->zap_f.zap_phys->zap_ptrtbl.zt_shift);
    err = zap_idx_to_blk(zap, idx, &blk);
    if (err != 0)
        return (err);
    err = zap_get_leaf_byblk(zap, blk, tx, lt, lp);

    ASSERT(err || ZAP_HASH_IDX(h, (*lp)->l_phys->l_hdr.lh_prefix_len) ==
        (*lp)->l_phys->l_hdr.lh_prefix);
    return (err);
}

static int
zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx, zap_leaf_t **lp)
{
    zap_t *zap = zn->zn_zap;
    uint64_t hash = zn->zn_hash;
    zap_leaf_t *nl;
    int prefix_diff, i, err;
    uint64_t sibling;
    int old_prefix_len = l->l_phys->l_hdr.lh_prefix_len;

    ASSERT3U(old_prefix_len, <=, zap->zap_f.zap_phys->zap_ptrtbl.zt_shift);
    ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));

    ASSERT3U(ZAP_HASH_IDX(hash, old_prefix_len), ==,
        l->l_phys->l_hdr.lh_prefix);

    if (zap_tryupgradedir(zap, tx) == 0 ||
        old_prefix_len == zap->zap_f.zap_phys->zap_ptrtbl.zt_shift) {
        /* We failed to upgrade, or need to grow the pointer table */
        objset_t *os = zap->zap_objset;
        uint64_t object = zap->zap_object;

        zap_put_leaf(l);
        zap_unlockdir(zap);
        err = zap_lockdir(os, object, tx, RW_WRITER,
            FALSE, FALSE, &zn->zn_zap);
        zap = zn->zn_zap;
        if (err)
            return (err);
        ASSERT(!zap->zap_ismicro);

        while (old_prefix_len ==
            zap->zap_f.zap_phys->zap_ptrtbl.zt_shift) {
            err = zap_grow_ptrtbl(zap, tx);
            if (err)
                return (err);
        }

        err = zap_deref_leaf(zap, hash, tx, RW_WRITER, &l);
        if (err)
            return (err);

        if (l->l_phys->l_hdr.lh_prefix_len != old_prefix_len) {
            /* it split while our locks were down */
            *lp = l;
            return (0);
        }
    }
    ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    ASSERT3U(old_prefix_len, <, zap->zap_f.zap_phys->zap_ptrtbl.zt_shift);
    ASSERT3U(ZAP_HASH_IDX(hash, old_prefix_len), ==,
        l->l_phys->l_hdr.lh_prefix);

    prefix_diff = zap->zap_f.zap_phys->zap_ptrtbl.zt_shift -
        (old_prefix_len + 1);
    sibling = (ZAP_HASH_IDX(hash, old_prefix_len + 1) | 1) << prefix_diff;

    /* check for i/o errors before doing zap_leaf_split */
    for (i = 0; i < (1ULL<<prefix_diff); i++) {
        uint64_t blk;
        err = zap_idx_to_blk(zap, sibling+i, &blk);
        if (err)
            return (err);
        ASSERT3U(blk, ==, l->l_blkid);
    }

    nl = zap_create_leaf(zap, tx);
    zap_leaf_split(l, nl, spa_version(dmu_objset_spa(zap->zap_objset)));

    /* set sibling pointers */
    for (i = 0; i < (1ULL<<prefix_diff); i++) {
        err = zap_set_idx_to_blk(zap, sibling+i, nl->l_blkid, tx);
        ASSERT3U(err, ==, 0); /* we checked for i/o errors above */
    }

    if (hash & (1ULL << (64 - l->l_phys->l_hdr.lh_prefix_len))) {
        /* we want the sibling */
        zap_put_leaf(l);
        *lp = nl;
    } else {
        zap_put_leaf(nl);
        *lp = l;
    }

    return (0);
}

static void
zap_put_leaf_maybe_grow_ptrtbl(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx)
{
    zap_t *zap = zn->zn_zap;
    int shift = zap->zap_f.zap_phys->zap_ptrtbl.zt_shift;
    int leaffull = (l->l_phys->l_hdr.lh_prefix_len == shift &&
        l->l_phys->l_hdr.lh_nfree < ZAP_LEAF_LOW_WATER);

    zap_put_leaf(l);

    if (leaffull || zap->zap_f.zap_phys->zap_ptrtbl.zt_nextblk) {
        int err;

        /*
         * We are in the middle of growing the pointer table, or
         * this leaf will soon make us grow it.
         */
        if (zap_tryupgradedir(zap, tx) == 0) {
            objset_t *os = zap->zap_objset;
            uint64_t zapobj = zap->zap_object;

            zap_unlockdir(zap);
            err = zap_lockdir(os, zapobj, tx,
                RW_WRITER, FALSE, FALSE, &zn->zn_zap);
            zap = zn->zn_zap;
            if (err)
                return;
        }

        /* could have finished growing while our locks were down */
        if (zap->zap_f.zap_phys->zap_ptrtbl.zt_shift == shift)
            (void) zap_grow_ptrtbl(zap, tx);
    }
}


static int
fzap_checksize(const char *name, uint64_t integer_size, uint64_t num_integers)
{
    if (name && strlen(name) > ZAP_MAXNAMELEN)
        return (E2BIG);

    /* Only integer sizes supported by C */
    switch (integer_size) {
    case 1:
    case 2:
    case 4:
    case 8:
        break;
    default:
        return (EINVAL);
    }

    if (integer_size * num_integers > ZAP_MAXVALUELEN)
        return (E2BIG);

    return (0);
}

/*
 * Routines for manipulating attributes.
 */
int
fzap_lookup(zap_name_t *zn,
    uint64_t integer_size, uint64_t num_integers, void *buf,
    char *realname, int rn_len, boolean_t *ncp)
{
    zap_leaf_t *l;
    int err;
    zap_entry_handle_t zeh;

    err = fzap_checksize(zn->zn_name_orij, integer_size, num_integers);
    if (err != 0)
        return (err);

    err = zap_deref_leaf(zn->zn_zap, zn->zn_hash, NULL, RW_READER, &l);
    if (err != 0)
        return (err);
    err = zap_leaf_lookup(l, zn, &zeh);
    if (err == 0) {
        err = zap_entry_read(&zeh, integer_size, num_integers, buf);
        (void) zap_entry_read_name(&zeh, rn_len, realname);
        if (ncp) {
            *ncp = zap_entry_normalization_conflict(&zeh,
                zn, NULL, zn->zn_zap);
        }
    }

    zap_put_leaf(l);
    return (err);
}

int
fzap_add_cd(zap_name_t *zn,
    uint64_t integer_size, uint64_t num_integers,
    const void *val, uint32_t cd, dmu_tx_t *tx)
{
    zap_leaf_t *l;
    int err;
    zap_entry_handle_t zeh;
    zap_t *zap = zn->zn_zap;

    ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    ASSERT(!zap->zap_ismicro);
    ASSERT(fzap_checksize(zn->zn_name_orij,
        integer_size, num_integers) == 0);

    err = zap_deref_leaf(zap, zn->zn_hash, tx, RW_WRITER, &l);
    if (err != 0)
        return (err);
retry:
    err = zap_leaf_lookup(l, zn, &zeh);
    if (err == 0) {
        err = EEXIST;
        goto out;
    }
    if (err != ENOENT)
        goto out;

    err = zap_entry_create(l, zn->zn_name_orij, zn->zn_hash, cd,
        integer_size, num_integers, val, &zeh);

    if (err == 0) {
        zap_increment_num_entries(zap, 1, tx);
    } else if (err == EAGAIN) {
        err = zap_expand_leaf(zn, l, tx, &l);
        zap = zn->zn_zap;   /* zap_expand_leaf() may change zap */
        if (err == 0)
            goto retry;
    }

out:
    if (zap != NULL)
        zap_put_leaf_maybe_grow_ptrtbl(zn, l, tx);
    return (err);
}

int
fzap_add(zap_name_t *zn,
    uint64_t integer_size, uint64_t num_integers,
    const void *val, dmu_tx_t *tx)
{
    int err = fzap_checksize(zn->zn_name_orij, integer_size, num_integers);
    if (err != 0)
        return (err);

    return (fzap_add_cd(zn, integer_size, num_integers,
        val, ZAP_MAXCD, tx));
}

int
fzap_update(zap_name_t *zn,
    int integer_size, uint64_t num_integers, const void *val, dmu_tx_t *tx)
{
    zap_leaf_t *l;
    int err, create;
    zap_entry_handle_t zeh;
    zap_t *zap = zn->zn_zap;

    ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    err = fzap_checksize(zn->zn_name_orij, integer_size, num_integers);
    if (err != 0)
        return (err);

    err = zap_deref_leaf(zap, zn->zn_hash, tx, RW_WRITER, &l);
    if (err != 0)
        return (err);
retry:
    err = zap_leaf_lookup(l, zn, &zeh);
    create = (err == ENOENT);
    ASSERT(err == 0 || err == ENOENT);

    if (create) {
        err = zap_entry_create(l, zn->zn_name_orij, zn->zn_hash,
            ZAP_MAXCD, integer_size, num_integers, val, &zeh);
        if (err == 0)
            zap_increment_num_entries(zap, 1, tx);
    } else {
        err = zap_entry_update(&zeh, integer_size, num_integers, val);
    }

    if (err == EAGAIN) {
        err = zap_expand_leaf(zn, l, tx, &l);
        zap = zn->zn_zap;   /* zap_expand_leaf() may change zap */
        if (err == 0)
            goto retry;
    }

    if (zap != NULL)
        zap_put_leaf_maybe_grow_ptrtbl(zn, l, tx);
    return (err);
}

int
fzap_length(zap_name_t *zn,
    uint64_t *integer_size, uint64_t *num_integers)
{
    zap_leaf_t *l;
    int err;
    zap_entry_handle_t zeh;

    err = zap_deref_leaf(zn->zn_zap, zn->zn_hash, NULL, RW_READER, &l);
    if (err != 0)
        return (err);
    err = zap_leaf_lookup(l, zn, &zeh);
    if (err != 0)
        goto out;

    if (integer_size)
        *integer_size = zeh.zeh_integer_size;
    if (num_integers)
        *num_integers = zeh.zeh_num_integers;
out:
    zap_put_leaf(l);
    return (err);
}

int
fzap_remove(zap_name_t *zn, dmu_tx_t *tx)
{
    zap_leaf_t *l;
    int err;
    zap_entry_handle_t zeh;

    err = zap_deref_leaf(zn->zn_zap, zn->zn_hash, tx, RW_WRITER, &l);
    if (err != 0)
        return (err);
    err = zap_leaf_lookup(l, zn, &zeh);
    if (err == 0) {
        zap_entry_remove(&zeh);
        zap_increment_num_entries(zn->zn_zap, -1, tx);
    }
    zap_put_leaf(l);
    return (err);
}

int
zap_value_search(objset_t *os, uint64_t zapobj, uint64_t value, uint64_t mask,
    char *name)
{
    zap_cursor_t zc;
    zap_attribute_t *za;
    int err;

    if (mask == 0)
        mask = -1ULL;

    za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
    for (zap_cursor_init(&zc, os, zapobj);
        (err = zap_cursor_retrieve(&zc, za)) == 0;
        zap_cursor_advance(&zc)) {
        if ((za->za_first_integer & mask) == (value & mask)) {
            (void) strcpy(name, za->za_name);
            break;
        }
    }
    zap_cursor_fini(&zc);
    kmem_free(za, sizeof (zap_attribute_t));
    return (err);
}


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

int
fzap_cursor_retrieve(zap_t *zap, zap_cursor_t *zc, zap_attribute_t *za)
{
    int err = ENOENT;
    zap_entry_handle_t zeh;
    zap_leaf_t *l;

    /* retrieve the next entry at or after zc_hash/zc_cd */
    /* if no entry, return ENOENT */

    if (zc->zc_leaf &&
        (ZAP_HASH_IDX(zc->zc_hash,
        zc->zc_leaf->l_phys->l_hdr.lh_prefix_len) !=
        zc->zc_leaf->l_phys->l_hdr.lh_prefix)) {
        rw_enter(&zc->zc_leaf->l_rwlock, RW_READER);
        zap_put_leaf(zc->zc_leaf);
        zc->zc_leaf = NULL;
    }

again:
    if (zc->zc_leaf == NULL) {
        err = zap_deref_leaf(zap, zc->zc_hash, NULL, RW_READER,
            &zc->zc_leaf);
        if (err != 0)
            return (err);
    } else {
        rw_enter(&zc->zc_leaf->l_rwlock, RW_READER);
    }
    l = zc->zc_leaf;

    err = zap_leaf_lookup_closest(l, zc->zc_hash, zc->zc_cd, &zeh);

    if (err == ENOENT) {
        uint64_t nocare =
            (1ULL << (64 - l->l_phys->l_hdr.lh_prefix_len)) - 1;
        zc->zc_hash = (zc->zc_hash & ~nocare) + nocare + 1;
        zc->zc_cd = 0;
        if (l->l_phys->l_hdr.lh_prefix_len == 0 || zc->zc_hash == 0) {
            zc->zc_hash = -1ULL;
        } else {
            zap_put_leaf(zc->zc_leaf);
            zc->zc_leaf = NULL;
            goto again;
        }
    }

    if (err == 0) {
        zc->zc_hash = zeh.zeh_hash;
        zc->zc_cd = zeh.zeh_cd;
        za->za_integer_length = zeh.zeh_integer_size;
        za->za_num_integers = zeh.zeh_num_integers;
        if (zeh.zeh_num_integers == 0) {
            za->za_first_integer = 0;
        } else {
            err = zap_entry_read(&zeh, 8, 1, &za->za_first_integer);
            ASSERT(err == 0 || err == EOVERFLOW);
        }
        err = zap_entry_read_name(&zeh,
            sizeof (za->za_name), za->za_name);
        ASSERT(err == 0);

        za->za_normalization_conflict =
            zap_entry_normalization_conflict(&zeh,
            NULL, za->za_name, zap);
    }
    rw_exit(&zc->zc_leaf->l_rwlock);
    return (err);
}


static void
zap_stats_ptrtbl(zap_t *zap, uint64_t *tbl, int len, zap_stats_t *zs)
{
    int i, err;
    uint64_t lastblk = 0;

    /*
     * NB: if a leaf has more pointers than an entire ptrtbl block
     * can hold, then it'll be accounted for more than once, since
     * we won't have lastblk.
     */
    for (i = 0; i < len; i++) {
        zap_leaf_t *l;

        if (tbl[i] == lastblk)
            continue;
        lastblk = tbl[i];

        err = zap_get_leaf_byblk(zap, tbl[i], NULL, RW_READER, &l);
        if (err == 0) {
            zap_leaf_stats(zap, l, zs);
            zap_put_leaf(l);
        }
    }
}

void
fzap_get_stats(zap_t *zap, zap_stats_t *zs)
{
    int bs = FZAP_BLOCK_SHIFT(zap);
    zs->zs_blocksize = 1ULL << bs;

    /*
     * Set zap_phys_t fields
     */
    zs->zs_num_leafs = zap->zap_f.zap_phys->zap_num_leafs;
    zs->zs_num_entries = zap->zap_f.zap_phys->zap_num_entries;
    zs->zs_num_blocks = zap->zap_f.zap_phys->zap_freeblk;
    zs->zs_block_type = zap->zap_f.zap_phys->zap_block_type;
    zs->zs_magic = zap->zap_f.zap_phys->zap_magic;
    zs->zs_salt = zap->zap_f.zap_phys->zap_salt;

    /*
     * Set zap_ptrtbl fields
     */
    zs->zs_ptrtbl_len = 1ULL << zap->zap_f.zap_phys->zap_ptrtbl.zt_shift;
    zs->zs_ptrtbl_nextblk = zap->zap_f.zap_phys->zap_ptrtbl.zt_nextblk;
    zs->zs_ptrtbl_blks_copied =
        zap->zap_f.zap_phys->zap_ptrtbl.zt_blks_copied;
    zs->zs_ptrtbl_zt_blk = zap->zap_f.zap_phys->zap_ptrtbl.zt_blk;
    zs->zs_ptrtbl_zt_numblks = zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks;
    zs->zs_ptrtbl_zt_shift = zap->zap_f.zap_phys->zap_ptrtbl.zt_shift;

    if (zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks == 0) {
        /* the ptrtbl is entirely in the header block. */
        zap_stats_ptrtbl(zap, &ZAP_EMBEDDED_PTRTBL_ENT(zap, 0),
            1 << ZAP_EMBEDDED_PTRTBL_SHIFT(zap), zs);
    } else {
        int b;

        dmu_prefetch(zap->zap_objset, zap->zap_object,
            zap->zap_f.zap_phys->zap_ptrtbl.zt_blk << bs,
            zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks << bs);

        for (b = 0; b < zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks;
            b++) {
            dmu_buf_t *db;
            int err;

            err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
                (zap->zap_f.zap_phys->zap_ptrtbl.zt_blk + b) << bs,
                FTAG, &db);
            if (err == 0) {
                zap_stats_ptrtbl(zap, db->db_data,
                    1<<(bs-3), zs);
                dmu_buf_rele(db, FTAG);
            }
        }
    }
}