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zap_micro.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 2008 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>

#ifdef _KERNEL
#include <sys/sunddi.h>
#endif

static int mzap_upgrade(zap_t **zapp, 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);
      buf->mz_normflags = BSWAP_64(buf->mz_normflags);
      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 int
mze_insert(zap_t *zap, int chunkid, uint64_t hash, mzap_ent_phys_t *mzep)
{
      mzap_ent_t *mze;
      avl_index_t idx;

      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;
      if (avl_find(&zap->zap_m.zap_avl, mze, &idx) != NULL) {
            kmem_free(mze, sizeof (mzap_ent_t));
            return (EEXIST);
      }
      avl_insert(&zap->zap_m.zap_avl, mze, idx);
      return (0);
}

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, NULL, RW_DEFAULT, 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, NULL,
                MUTEX_DEFAULT, 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;

                        zn = zap_name_alloc(zap, mze->mze_name,
                            MT_EXACT);
                        if (mze_insert(zap, i, zn->zn_hash, mze) == 0)
                              zap->zap_m.zap_num_entries++;
                        else {
                              printf("ZFS WARNING: Duplicated ZAP "
                                  "entry detected (%s).\n",
                                  mze->mze_name);
                        }
                        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);
                  *zapp = zap;
                  return (mzap_upgrade(zapp, tx));
            }
            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 int
mzap_upgrade(zap_t **zapp, dmu_tx_t *tx)
{
      mzap_phys_t *mzp;
      int i, sz, nchunks, err;
      zap_t *zap = *zapp;

      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);
      if (err) {
            kmem_free(mzp, sz);
            return (err);
      }

      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 = zn->zn_zap; /* fzap_add_cd() may change zap */
            zap_name_free(zn);
            if (err)
                  break;
      }
      kmem_free(mzp, sz);
      *zapp = zap;
      return (err);
}

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;

      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;
                  VERIFY(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);
            zap = zn->zn_zap; /* fzap_add() may change zap */
      } 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);
            err = mzap_upgrade(&zn->zn_zap, tx);
            if (err == 0)
                  err = fzap_add(zn, integer_size, num_integers, val, tx);
            zap = zn->zn_zap; /* fzap_add() may change zap */
      } else {
            mze = mze_find(zn);
            if (mze != NULL) {
                  err = EEXIST;
            } else {
                  mzap_addent(zn, *intval);
            }
      }
      ASSERT(zap == zn->zn_zap);
      zap_name_free(zn);
      if (zap != NULL)  /* may be NULL if fzap_add() failed */
            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);
            zap = zn->zn_zap; /* fzap_update() may change zap */
      } 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);
            err = mzap_upgrade(&zn->zn_zap, tx);
            if (err == 0)
                  err = fzap_update(zn, integer_size, num_integers,
                      val, tx);
            zap = zn->zn_zap; /* fzap_update() may change zap */
      } 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);
            }
      }
      ASSERT(zap == zn->zn_zap);
      zap_name_free(zn);
      if (zap != NULL)  /* may be NULL if fzap_upgrade() failed */
            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);
}

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