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zap.c

/*
 * 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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * 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/zfs_znode.h>
#include <sys/fs/zfs.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, zp->zap_normflags != 0);

      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, zap->zap_normflags != 0);

      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, zap->zap_normflags != 0);

      /* 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);
}

/*
 * Helper functions for consumers.
 */

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);
}

int
zap_join(objset_t *os, uint64_t fromobj, uint64_t intoobj, dmu_tx_t *tx)
{
      zap_cursor_t zc;
      zap_attribute_t za;
      int err;

      for (zap_cursor_init(&zc, os, fromobj);
          zap_cursor_retrieve(&zc, &za) == 0;
          (void) zap_cursor_advance(&zc)) {
            if (za.za_integer_length != 8 || za.za_num_integers != 1)
                  return (EINVAL);
            err = zap_add(os, intoobj, za.za_name,
                8, 1, &za.za_first_integer, tx);
            if (err)
                  return (err);
      }
      zap_cursor_fini(&zc);
      return (0);
}

int
zap_add_int(objset_t *os, uint64_t obj, uint64_t value, dmu_tx_t *tx)
{
      char name[20];

      (void) snprintf(name, sizeof (name), "%llx", (longlong_t)value);
      return (zap_add(os, obj, name, 8, 1, &value, tx));
}

int
zap_remove_int(objset_t *os, uint64_t obj, uint64_t value, dmu_tx_t *tx)
{
      char name[20];

      (void) snprintf(name, sizeof (name), "%llx", (longlong_t)value);
      return (zap_remove(os, obj, name, tx));
}

int
zap_lookup_int(objset_t *os, uint64_t obj, uint64_t value)
{
      char name[20];

      (void) snprintf(name, sizeof (name), "%llx", (longlong_t)value);
      return (zap_lookup(os, obj, name, 8, 1, &value));
}

/*
 * 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);
                  }
            }
      }
}

int
fzap_count_write(zap_name_t *zn, int add, uint64_t *towrite,
    uint64_t *tooverwrite)
{
      zap_t *zap = zn->zn_zap;
      zap_leaf_t *l;
      int err;

      /*
       * Account for the header block of the fatzap.
       */
      if (!add && dmu_buf_freeable(zap->zap_dbuf)) {
            tooverwrite += zap->zap_dbuf->db_size;
      } else {
            towrite += zap->zap_dbuf->db_size;
      }

      /*
       * Account for the pointer table blocks.
       * If we are adding we need to account for the following cases :
       * - If the pointer table is embedded, this operation could force an
       *   external pointer table.
       * - If this already has an external pointer table this operation
       *   could extend the table.
       */
      if (add) {
            if (zap->zap_f.zap_phys->zap_ptrtbl.zt_blk == 0)
                  towrite += zap->zap_dbuf->db_size;
            else
                  towrite += (zap->zap_dbuf->db_size * 3);
      }

      /*
       * Now, check if the block containing leaf is freeable
       * and account accordingly.
       */
      err = zap_deref_leaf(zap, zn->zn_hash, NULL, RW_READER, &l);
      if (err != 0) {
            return (err);
      }

      if (!add && dmu_buf_freeable(l->l_dbuf)) {
            tooverwrite += l->l_dbuf->db_size;
      } else {
            /*
             * If this an add operation, the leaf block could split.
             * Hence, we need to account for an additional leaf block.
             */
            towrite += (add ? 2 : 1) * l->l_dbuf->db_size;
      }

      zap_put_leaf(l);
      return (0);
}

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