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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 /*
     22  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
     23  * Use is subject to license terms.
     24  */
     25 
     26 /*
     27  * This file contains the top half of the zfs directory structure
     28  * implementation. The bottom half is in zap_leaf.c.
     29  *
     30  * The zdir is an extendable hash data structure. There is a table of
     31  * pointers to buckets (zap_t->zd_data->zd_leafs). The buckets are
     32  * each a constant size and hold a variable number of directory entries.
     33  * The buckets (aka "leaf nodes") are implemented in zap_leaf.c.
     34  *
     35  * The pointer table holds a power of 2 number of pointers.
     36  * (1<<zap_t->zd_data->zd_phys->zd_prefix_len).  The bucket pointed to
     37  * by the pointer at index i in the table holds entries whose hash value
     38  * has a zd_prefix_len - bit prefix
     39  */
     40 
     41 #include <sys/spa.h>
     42 #include <sys/dmu.h>
     43 #include <sys/zfs_context.h>
     44 #include <sys/zfs_znode.h>
     45 #include <sys/fs/zfs.h>
     46 #include <sys/zap.h>
     47 #include <sys/refcount.h>
     48 #include <sys/zap_impl.h>
     49 #include <sys/zap_leaf.h>
     50 
     51 int fzap_default_block_shift = 14; /* 16k blocksize */
     52 
     53 static void zap_leaf_pageout(dmu_buf_t *db, void *vl);
     54 static uint64_t zap_allocate_blocks(zap_t *zap, int nblocks);
     55 
     56 
     57 void
     58 fzap_byteswap(void *vbuf, size_t size)
     59 {
     60 	uint64_t block_type;
     61 
     62 	block_type = *(uint64_t *)vbuf;
     63 
     64 	if (block_type == ZBT_LEAF || block_type == BSWAP_64(ZBT_LEAF))
     65 		zap_leaf_byteswap(vbuf, size);
     66 	else {
     67 		/* it's a ptrtbl block */
     68 		byteswap_uint64_array(vbuf, size);
     69 	}
     70 }
     71 
     72 void
     73 fzap_upgrade(zap_t *zap, dmu_tx_t *tx, zap_flags_t flags)
     74 {
     75 	dmu_buf_t *db;
     76 	zap_leaf_t *l;
     77 	int i;
     78 	zap_phys_t *zp;
     79 
     80 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
     81 	zap->zap_ismicro = FALSE;
     82 
     83 	(void) dmu_buf_update_user(zap->zap_dbuf, zap, zap,
     84 	    &zap->zap_f.zap_phys, zap_evict);
     85 
     86 	mutex_init(&zap->zap_f.zap_num_entries_mtx, 0, 0, 0);
     87 	zap->zap_f.zap_block_shift = highbit(zap->zap_dbuf->db_size) - 1;
     88 
     89 	zp = zap->zap_f.zap_phys;
     90 	/*
     91 	 * explicitly zero it since it might be coming from an
     92 	 * initialized microzap
     93 	 */
     94 	bzero(zap->zap_dbuf->db_data, zap->zap_dbuf->db_size);
     95 	zp->zap_block_type = ZBT_HEADER;
     96 	zp->zap_magic = ZAP_MAGIC;
     97 
     98 	zp->zap_ptrtbl.zt_shift = ZAP_EMBEDDED_PTRTBL_SHIFT(zap);
     99 
    100 	zp->zap_freeblk = 2;		/* block 1 will be the first leaf */
    101 	zp->zap_num_leafs = 1;
    102 	zp->zap_num_entries = 0;
    103 	zp->zap_salt = zap->zap_salt;
    104 	zp->zap_normflags = zap->zap_normflags;
    105 	zp->zap_flags = flags;
    106 
    107 	/* block 1 will be the first leaf */
    108 	for (i = 0; i < (1<<zp->zap_ptrtbl.zt_shift); i++)
    109 		ZAP_EMBEDDED_PTRTBL_ENT(zap, i) = 1;
    110 
    111 	/*
    112 	 * set up block 1 - the first leaf
    113 	 */
    114 	VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
    115 	    1<<FZAP_BLOCK_SHIFT(zap), FTAG, &db));
    116 	dmu_buf_will_dirty(db, tx);
    117 
    118 	l = kmem_zalloc(sizeof (zap_leaf_t), KM_SLEEP);
    119 	l->l_dbuf = db;
    120 	l->l_phys = db->db_data;
    121 
    122 	zap_leaf_init(l, zp->zap_normflags != 0);
    123 
    124 	kmem_free(l, sizeof (zap_leaf_t));
    125 	dmu_buf_rele(db, FTAG);
    126 }
    127 
    128 static int
    129 zap_tryupgradedir(zap_t *zap, dmu_tx_t *tx)
    130 {
    131 	if (RW_WRITE_HELD(&zap->zap_rwlock))
    132 		return (1);
    133 	if (rw_tryupgrade(&zap->zap_rwlock)) {
    134 		dmu_buf_will_dirty(zap->zap_dbuf, tx);
    135 		return (1);
    136 	}
    137 	return (0);
    138 }
    139 
    140 /*
    141  * Generic routines for dealing with the pointer & cookie tables.
    142  */
    143 
    144 static int
    145 zap_table_grow(zap_t *zap, zap_table_phys_t *tbl,
    146     void (*transfer_func)(const uint64_t *src, uint64_t *dst, int n),
    147     dmu_tx_t *tx)
    148 {
    149 	uint64_t b, newblk;
    150 	dmu_buf_t *db_old, *db_new;
    151 	int err;
    152 	int bs = FZAP_BLOCK_SHIFT(zap);
    153 	int hepb = 1<<(bs-4);
    154 	/* hepb = half the number of entries in a block */
    155 
    156 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    157 	ASSERT(tbl->zt_blk != 0);
    158 	ASSERT(tbl->zt_numblks > 0);
    159 
    160 	if (tbl->zt_nextblk != 0) {
    161 		newblk = tbl->zt_nextblk;
    162 	} else {
    163 		newblk = zap_allocate_blocks(zap, tbl->zt_numblks * 2);
    164 		tbl->zt_nextblk = newblk;
    165 		ASSERT3U(tbl->zt_blks_copied, ==, 0);
    166 		dmu_prefetch(zap->zap_objset, zap->zap_object,
    167 		    tbl->zt_blk << bs, tbl->zt_numblks << bs);
    168 	}
    169 
    170 	/*
    171 	 * Copy the ptrtbl from the old to new location.
    172 	 */
    173 
    174 	b = tbl->zt_blks_copied;
    175 	err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
    176 	    (tbl->zt_blk + b) << bs, FTAG, &db_old);
    177 	if (err)
    178 		return (err);
    179 
    180 	/* first half of entries in old[b] go to new[2*b+0] */
    181 	VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
    182 	    (newblk + 2*b+0) << bs, FTAG, &db_new));
    183 	dmu_buf_will_dirty(db_new, tx);
    184 	transfer_func(db_old->db_data, db_new->db_data, hepb);
    185 	dmu_buf_rele(db_new, FTAG);
    186 
    187 	/* second half of entries in old[b] go to new[2*b+1] */
    188 	VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
    189 	    (newblk + 2*b+1) << bs, FTAG, &db_new));
    190 	dmu_buf_will_dirty(db_new, tx);
    191 	transfer_func((uint64_t *)db_old->db_data + hepb,
    192 	    db_new->db_data, hepb);
    193 	dmu_buf_rele(db_new, FTAG);
    194 
    195 	dmu_buf_rele(db_old, FTAG);
    196 
    197 	tbl->zt_blks_copied++;
    198 
    199 	dprintf("copied block %llu of %llu\n",
    200 	    tbl->zt_blks_copied, tbl->zt_numblks);
    201 
    202 	if (tbl->zt_blks_copied == tbl->zt_numblks) {
    203 		(void) dmu_free_range(zap->zap_objset, zap->zap_object,
    204 		    tbl->zt_blk << bs, tbl->zt_numblks << bs, tx);
    205 
    206 		tbl->zt_blk = newblk;
    207 		tbl->zt_numblks *= 2;
    208 		tbl->zt_shift++;
    209 		tbl->zt_nextblk = 0;
    210 		tbl->zt_blks_copied = 0;
    211 
    212 		dprintf("finished; numblocks now %llu (%lluk entries)\n",
    213 		    tbl->zt_numblks, 1<<(tbl->zt_shift-10));
    214 	}
    215 
    216 	return (0);
    217 }
    218 
    219 static int
    220 zap_table_store(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t val,
    221     dmu_tx_t *tx)
    222 {
    223 	int err;
    224 	uint64_t blk, off;
    225 	int bs = FZAP_BLOCK_SHIFT(zap);
    226 	dmu_buf_t *db;
    227 
    228 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    229 	ASSERT(tbl->zt_blk != 0);
    230 
    231 	dprintf("storing %llx at index %llx\n", val, idx);
    232 
    233 	blk = idx >> (bs-3);
    234 	off = idx & ((1<<(bs-3))-1);
    235 
    236 	err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
    237 	    (tbl->zt_blk + blk) << bs, FTAG, &db);
    238 	if (err)
    239 		return (err);
    240 	dmu_buf_will_dirty(db, tx);
    241 
    242 	if (tbl->zt_nextblk != 0) {
    243 		uint64_t idx2 = idx * 2;
    244 		uint64_t blk2 = idx2 >> (bs-3);
    245 		uint64_t off2 = idx2 & ((1<<(bs-3))-1);
    246 		dmu_buf_t *db2;
    247 
    248 		err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
    249 		    (tbl->zt_nextblk + blk2) << bs, FTAG, &db2);
    250 		if (err) {
    251 			dmu_buf_rele(db, FTAG);
    252 			return (err);
    253 		}
    254 		dmu_buf_will_dirty(db2, tx);
    255 		((uint64_t *)db2->db_data)[off2] = val;
    256 		((uint64_t *)db2->db_data)[off2+1] = val;
    257 		dmu_buf_rele(db2, FTAG);
    258 	}
    259 
    260 	((uint64_t *)db->db_data)[off] = val;
    261 	dmu_buf_rele(db, FTAG);
    262 
    263 	return (0);
    264 }
    265 
    266 static int
    267 zap_table_load(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t *valp)
    268 {
    269 	uint64_t blk, off;
    270 	int err;
    271 	dmu_buf_t *db;
    272 	int bs = FZAP_BLOCK_SHIFT(zap);
    273 
    274 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    275 
    276 	blk = idx >> (bs-3);
    277 	off = idx & ((1<<(bs-3))-1);
    278 
    279 	err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
    280 	    (tbl->zt_blk + blk) << bs, FTAG, &db);
    281 	if (err)
    282 		return (err);
    283 	*valp = ((uint64_t *)db->db_data)[off];
    284 	dmu_buf_rele(db, FTAG);
    285 
    286 	if (tbl->zt_nextblk != 0) {
    287 		/*
    288 		 * read the nextblk for the sake of i/o error checking,
    289 		 * so that zap_table_load() will catch errors for
    290 		 * zap_table_store.
    291 		 */
    292 		blk = (idx*2) >> (bs-3);
    293 
    294 		err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
    295 		    (tbl->zt_nextblk + blk) << bs, FTAG, &db);
    296 		dmu_buf_rele(db, FTAG);
    297 	}
    298 	return (err);
    299 }
    300 
    301 /*
    302  * Routines for growing the ptrtbl.
    303  */
    304 
    305 static void
    306 zap_ptrtbl_transfer(const uint64_t *src, uint64_t *dst, int n)
    307 {
    308 	int i;
    309 	for (i = 0; i < n; i++) {
    310 		uint64_t lb = src[i];
    311 		dst[2*i+0] = lb;
    312 		dst[2*i+1] = lb;
    313 	}
    314 }
    315 
    316 static int
    317 zap_grow_ptrtbl(zap_t *zap, dmu_tx_t *tx)
    318 {
    319 	/*
    320 	 * The pointer table should never use more hash bits than we
    321 	 * have (otherwise we'd be using useless zero bits to index it).
    322 	 * If we are within 2 bits of running out, stop growing, since
    323 	 * this is already an aberrant condition.
    324 	 */
    325 	if (zap->zap_f.zap_phys->zap_ptrtbl.zt_shift >= zap_hashbits(zap) - 2)
    326 		return (ENOSPC);
    327 
    328 	if (zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks == 0) {
    329 		/*
    330 		 * We are outgrowing the "embedded" ptrtbl (the one
    331 		 * stored in the header block).  Give it its own entire
    332 		 * block, which will double the size of the ptrtbl.
    333 		 */
    334 		uint64_t newblk;
    335 		dmu_buf_t *db_new;
    336 		int err;
    337 
    338 		ASSERT3U(zap->zap_f.zap_phys->zap_ptrtbl.zt_shift, ==,
    339 		    ZAP_EMBEDDED_PTRTBL_SHIFT(zap));
    340 		ASSERT3U(zap->zap_f.zap_phys->zap_ptrtbl.zt_blk, ==, 0);
    341 
    342 		newblk = zap_allocate_blocks(zap, 1);
    343 		err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
    344 		    newblk << FZAP_BLOCK_SHIFT(zap), FTAG, &db_new);
    345 		if (err)
    346 			return (err);
    347 		dmu_buf_will_dirty(db_new, tx);
    348 		zap_ptrtbl_transfer(&ZAP_EMBEDDED_PTRTBL_ENT(zap, 0),
    349 		    db_new->db_data, 1 << ZAP_EMBEDDED_PTRTBL_SHIFT(zap));
    350 		dmu_buf_rele(db_new, FTAG);
    351 
    352 		zap->zap_f.zap_phys->zap_ptrtbl.zt_blk = newblk;
    353 		zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks = 1;
    354 		zap->zap_f.zap_phys->zap_ptrtbl.zt_shift++;
    355 
    356 		ASSERT3U(1ULL << zap->zap_f.zap_phys->zap_ptrtbl.zt_shift, ==,
    357 		    zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks <<
    358 		    (FZAP_BLOCK_SHIFT(zap)-3));
    359 
    360 		return (0);
    361 	} else {
    362 		return (zap_table_grow(zap, &zap->zap_f.zap_phys->zap_ptrtbl,
    363 		    zap_ptrtbl_transfer, tx));
    364 	}
    365 }
    366 
    367 static void
    368 zap_increment_num_entries(zap_t *zap, int delta, dmu_tx_t *tx)
    369 {
    370 	dmu_buf_will_dirty(zap->zap_dbuf, tx);
    371 	mutex_enter(&zap->zap_f.zap_num_entries_mtx);
    372 	ASSERT(delta > 0 || zap->zap_f.zap_phys->zap_num_entries >= -delta);
    373 	zap->zap_f.zap_phys->zap_num_entries += delta;
    374 	mutex_exit(&zap->zap_f.zap_num_entries_mtx);
    375 }
    376 
    377 static uint64_t
    378 zap_allocate_blocks(zap_t *zap, int nblocks)
    379 {
    380 	uint64_t newblk;
    381 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    382 	newblk = zap->zap_f.zap_phys->zap_freeblk;
    383 	zap->zap_f.zap_phys->zap_freeblk += nblocks;
    384 	return (newblk);
    385 }
    386 
    387 static zap_leaf_t *
    388 zap_create_leaf(zap_t *zap, dmu_tx_t *tx)
    389 {
    390 	void *winner;
    391 	zap_leaf_t *l = kmem_alloc(sizeof (zap_leaf_t), KM_SLEEP);
    392 
    393 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    394 
    395 	rw_init(&l->l_rwlock, 0, 0, 0);
    396 	rw_enter(&l->l_rwlock, RW_WRITER);
    397 	l->l_blkid = zap_allocate_blocks(zap, 1);
    398 	l->l_dbuf = NULL;
    399 	l->l_phys = NULL;
    400 
    401 	VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
    402 	    l->l_blkid << FZAP_BLOCK_SHIFT(zap), NULL, &l->l_dbuf));
    403 	winner = dmu_buf_set_user(l->l_dbuf, l, &l->l_phys, zap_leaf_pageout);
    404 	ASSERT(winner == NULL);
    405 	dmu_buf_will_dirty(l->l_dbuf, tx);
    406 
    407 	zap_leaf_init(l, zap->zap_normflags != 0);
    408 
    409 	zap->zap_f.zap_phys->zap_num_leafs++;
    410 
    411 	return (l);
    412 }
    413 
    414 int
    415 fzap_count(zap_t *zap, uint64_t *count)
    416 {
    417 	ASSERT(!zap->zap_ismicro);
    418 	mutex_enter(&zap->zap_f.zap_num_entries_mtx); /* unnecessary */
    419 	*count = zap->zap_f.zap_phys->zap_num_entries;
    420 	mutex_exit(&zap->zap_f.zap_num_entries_mtx);
    421 	return (0);
    422 }
    423 
    424 /*
    425  * Routines for obtaining zap_leaf_t's
    426  */
    427 
    428 void
    429 zap_put_leaf(zap_leaf_t *l)
    430 {
    431 	rw_exit(&l->l_rwlock);
    432 	dmu_buf_rele(l->l_dbuf, NULL);
    433 }
    434 
    435 _NOTE(ARGSUSED(0))
    436 static void
    437 zap_leaf_pageout(dmu_buf_t *db, void *vl)
    438 {
    439 	zap_leaf_t *l = vl;
    440 
    441 	rw_destroy(&l->l_rwlock);
    442 	kmem_free(l, sizeof (zap_leaf_t));
    443 }
    444 
    445 static zap_leaf_t *
    446 zap_open_leaf(uint64_t blkid, dmu_buf_t *db)
    447 {
    448 	zap_leaf_t *l, *winner;
    449 
    450 	ASSERT(blkid != 0);
    451 
    452 	l = kmem_alloc(sizeof (zap_leaf_t), KM_SLEEP);
    453 	rw_init(&l->l_rwlock, 0, 0, 0);
    454 	rw_enter(&l->l_rwlock, RW_WRITER);
    455 	l->l_blkid = blkid;
    456 	l->l_bs = highbit(db->db_size)-1;
    457 	l->l_dbuf = db;
    458 	l->l_phys = NULL;
    459 
    460 	winner = dmu_buf_set_user(db, l, &l->l_phys, zap_leaf_pageout);
    461 
    462 	rw_exit(&l->l_rwlock);
    463 	if (winner != NULL) {
    464 		/* someone else set it first */
    465 		zap_leaf_pageout(NULL, l);
    466 		l = winner;
    467 	}
    468 
    469 	/*
    470 	 * lhr_pad was previously used for the next leaf in the leaf
    471 	 * chain.  There should be no chained leafs (as we have removed
    472 	 * support for them).
    473 	 */
    474 	ASSERT3U(l->l_phys->l_hdr.lh_pad1, ==, 0);
    475 
    476 	/*
    477 	 * There should be more hash entries than there can be
    478 	 * chunks to put in the hash table
    479 	 */
    480 	ASSERT3U(ZAP_LEAF_HASH_NUMENTRIES(l), >, ZAP_LEAF_NUMCHUNKS(l) / 3);
    481 
    482 	/* The chunks should begin at the end of the hash table */
    483 	ASSERT3P(&ZAP_LEAF_CHUNK(l, 0), ==,
    484 	    &l->l_phys->l_hash[ZAP_LEAF_HASH_NUMENTRIES(l)]);
    485 
    486 	/* The chunks should end at the end of the block */
    487 	ASSERT3U((uintptr_t)&ZAP_LEAF_CHUNK(l, ZAP_LEAF_NUMCHUNKS(l)) -
    488 	    (uintptr_t)l->l_phys, ==, l->l_dbuf->db_size);
    489 
    490 	return (l);
    491 }
    492 
    493 static int
    494 zap_get_leaf_byblk(zap_t *zap, uint64_t blkid, dmu_tx_t *tx, krw_t lt,
    495     zap_leaf_t **lp)
    496 {
    497 	dmu_buf_t *db;
    498 	zap_leaf_t *l;
    499 	int bs = FZAP_BLOCK_SHIFT(zap);
    500 	int err;
    501 
    502 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    503 
    504 	err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
    505 	    blkid << bs, NULL, &db);
    506 	if (err)
    507 		return (err);
    508 
    509 	ASSERT3U(db->db_object, ==, zap->zap_object);
    510 	ASSERT3U(db->db_offset, ==, blkid << bs);
    511 	ASSERT3U(db->db_size, ==, 1 << bs);
    512 	ASSERT(blkid != 0);
    513 
    514 	l = dmu_buf_get_user(db);
    515 
    516 	if (l == NULL)
    517 		l = zap_open_leaf(blkid, db);
    518 
    519 	rw_enter(&l->l_rwlock, lt);
    520 	/*
    521 	 * Must lock before dirtying, otherwise l->l_phys could change,
    522 	 * causing ASSERT below to fail.
    523 	 */
    524 	if (lt == RW_WRITER)
    525 		dmu_buf_will_dirty(db, tx);
    526 	ASSERT3U(l->l_blkid, ==, blkid);
    527 	ASSERT3P(l->l_dbuf, ==, db);
    528 	ASSERT3P(l->l_phys, ==, l->l_dbuf->db_data);
    529 	ASSERT3U(l->l_phys->l_hdr.lh_block_type, ==, ZBT_LEAF);
    530 	ASSERT3U(l->l_phys->l_hdr.lh_magic, ==, ZAP_LEAF_MAGIC);
    531 
    532 	*lp = l;
    533 	return (0);
    534 }
    535 
    536 static int
    537 zap_idx_to_blk(zap_t *zap, uint64_t idx, uint64_t *valp)
    538 {
    539 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    540 
    541 	if (zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks == 0) {
    542 		ASSERT3U(idx, <,
    543 		    (1ULL << zap->zap_f.zap_phys->zap_ptrtbl.zt_shift));
    544 		*valp = ZAP_EMBEDDED_PTRTBL_ENT(zap, idx);
    545 		return (0);
    546 	} else {
    547 		return (zap_table_load(zap, &zap->zap_f.zap_phys->zap_ptrtbl,
    548 		    idx, valp));
    549 	}
    550 }
    551 
    552 static int
    553 zap_set_idx_to_blk(zap_t *zap, uint64_t idx, uint64_t blk, dmu_tx_t *tx)
    554 {
    555 	ASSERT(tx != NULL);
    556 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    557 
    558 	if (zap->zap_f.zap_phys->zap_ptrtbl.zt_blk == 0) {
    559 		ZAP_EMBEDDED_PTRTBL_ENT(zap, idx) = blk;
    560 		return (0);
    561 	} else {
    562 		return (zap_table_store(zap, &zap->zap_f.zap_phys->zap_ptrtbl,
    563 		    idx, blk, tx));
    564 	}
    565 }
    566 
    567 static int
    568 zap_deref_leaf(zap_t *zap, uint64_t h, dmu_tx_t *tx, krw_t lt, zap_leaf_t **lp)
    569 {
    570 	uint64_t idx, blk;
    571 	int err;
    572 
    573 	ASSERT(zap->zap_dbuf == NULL ||
    574 	    zap->zap_f.zap_phys == zap->zap_dbuf->db_data);
    575 	ASSERT3U(zap->zap_f.zap_phys->zap_magic, ==, ZAP_MAGIC);
    576 	idx = ZAP_HASH_IDX(h, zap->zap_f.zap_phys->zap_ptrtbl.zt_shift);
    577 	err = zap_idx_to_blk(zap, idx, &blk);
    578 	if (err != 0)
    579 		return (err);
    580 	err = zap_get_leaf_byblk(zap, blk, tx, lt, lp);
    581 
    582 	ASSERT(err || ZAP_HASH_IDX(h, (*lp)->l_phys->l_hdr.lh_prefix_len) ==
    583 	    (*lp)->l_phys->l_hdr.lh_prefix);
    584 	return (err);
    585 }
    586 
    587 static int
    588 zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx, zap_leaf_t **lp)
    589 {
    590 	zap_t *zap = zn->zn_zap;
    591 	uint64_t hash = zn->zn_hash;
    592 	zap_leaf_t *nl;
    593 	int prefix_diff, i, err;
    594 	uint64_t sibling;
    595 	int old_prefix_len = l->l_phys->l_hdr.lh_prefix_len;
    596 
    597 	ASSERT3U(old_prefix_len, <=, zap->zap_f.zap_phys->zap_ptrtbl.zt_shift);
    598 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    599 
    600 	ASSERT3U(ZAP_HASH_IDX(hash, old_prefix_len), ==,
    601 	    l->l_phys->l_hdr.lh_prefix);
    602 
    603 	if (zap_tryupgradedir(zap, tx) == 0 ||
    604 	    old_prefix_len == zap->zap_f.zap_phys->zap_ptrtbl.zt_shift) {
    605 		/* We failed to upgrade, or need to grow the pointer table */
    606 		objset_t *os = zap->zap_objset;
    607 		uint64_t object = zap->zap_object;
    608 
    609 		zap_put_leaf(l);
    610 		zap_unlockdir(zap);
    611 		err = zap_lockdir(os, object, tx, RW_WRITER,
    612 		    FALSE, FALSE, &zn->zn_zap);
    613 		zap = zn->zn_zap;
    614 		if (err)
    615 			return (err);
    616 		ASSERT(!zap->zap_ismicro);
    617 
    618 		while (old_prefix_len ==
    619 		    zap->zap_f.zap_phys->zap_ptrtbl.zt_shift) {
    620 			err = zap_grow_ptrtbl(zap, tx);
    621 			if (err)
    622 				return (err);
    623 		}
    624 
    625 		err = zap_deref_leaf(zap, hash, tx, RW_WRITER, &l);
    626 		if (err)
    627 			return (err);
    628 
    629 		if (l->l_phys->l_hdr.lh_prefix_len != old_prefix_len) {
    630 			/* it split while our locks were down */
    631 			*lp = l;
    632 			return (0);
    633 		}
    634 	}
    635 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
    636 	ASSERT3U(old_prefix_len, <, zap->zap_f.zap_phys->zap_ptrtbl.zt_shift);
    637 	ASSERT3U(ZAP_HASH_IDX(hash, old_prefix_len), ==,
    638 	    l->l_phys->l_hdr.lh_prefix);
    639 
    640 	prefix_diff = zap->zap_f.zap_phys->zap_ptrtbl.zt_shift -
    641 	    (old_prefix_len + 1);
    642 	sibling = (ZAP_HASH_IDX(hash, old_prefix_len + 1) | 1) << prefix_diff;
    643 
    644 	/* check for i/o errors before doing zap_leaf_split */
    645 	for (i = 0; i < (1ULL<<prefix_diff); i++) {
    646 		uint64_t blk;
    647 		err = zap_idx_to_blk(zap, sibling+i, &blk);
    648 		if (err)
    649 			return (err);
    650 		ASSERT3U(blk, ==, l->l_blkid);
    651 	}
    652 
    653 	nl = zap_create_leaf(zap, tx);
    654 	zap_leaf_split(l, nl, zap->zap_normflags != 0);
    655 
    656 	/* set sibling pointers */
    657 	for (i = 0; i < (1ULL<<prefix_diff); i++) {
    658 		err = zap_set_idx_to_blk(zap, sibling+i, nl->l_blkid, tx);
    659 		ASSERT3U(err, ==, 0); /* we checked for i/o errors above */
    660 	}
    661 
    662 	if (hash & (1ULL << (64 - l->l_phys->l_hdr.lh_prefix_len))) {
    663 		/* we want the sibling */
    664 		zap_put_leaf(l);
    665 		*lp = nl;
    666 	} else {
    667 		zap_put_leaf(nl);
    668 		*lp = l;
    669 	}
    670 
    671 	return (0);
    672 }
    673 
    674 static void
    675 zap_put_leaf_maybe_grow_ptrtbl(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx)
    676 {
    677 	zap_t *zap = zn->zn_zap;
    678 	int shift = zap->zap_f.zap_phys->zap_ptrtbl.zt_shift;
    679 	int leaffull = (l->l_phys->l_hdr.lh_prefix_len == shift &&
    680 	    l->l_phys->l_hdr.lh_nfree < ZAP_LEAF_LOW_WATER);
    681 
    682 	zap_put_leaf(l);
    683 
    684 	if (leaffull || zap->zap_f.zap_phys->zap_ptrtbl.zt_nextblk) {
    685 		int err;
    686 
    687 		/*
    688 		 * We are in the middle of growing the pointer table, or
    689 		 * this leaf will soon make us grow it.
    690 		 */
    691 		if (zap_tryupgradedir(zap, tx) == 0) {
    692 			objset_t *os = zap->zap_objset;
    693 			uint64_t zapobj = zap->zap_object;
    694 
    695 			zap_unlockdir(zap);
    696 			err = zap_lockdir(os, zapobj, tx,
    697 			    RW_WRITER, FALSE, FALSE, &zn->zn_zap);
    698 			zap = zn->zn_zap;
    699 			if (err)
    700 				return;
    701 		}
    702 
    703 		/* could have finished growing while our locks were down */
    704 		if (zap->zap_f.zap_phys->zap_ptrtbl.zt_shift == shift)
    705 			(void) zap_grow_ptrtbl(zap, tx);
    706 	}
    707 }
    708 
    709 
    710 static int
    711 fzap_checksize(zap_name_t *zn, uint64_t integer_size, uint64_t num_integers)
    712 {
    713 	if (zn->zn_key_orig_len > ZAP_MAXNAMELEN)
    714 		return (E2BIG);
    715 
    716 	/* Only integer sizes supported by C */
    717 	switch (integer_size) {
    718 	case 1:
    719 	case 2:
    720 	case 4:
    721 	case 8:
    722 		break;
    723 	default:
    724 		return (EINVAL);
    725 	}
    726 
    727 	if (integer_size * num_integers > ZAP_MAXVALUELEN)
    728 		return (E2BIG);
    729 
    730 	return (0);
    731 }
    732 
    733 /*
    734  * Routines for manipulating attributes.
    735  */
    736 int
    737 fzap_lookup(zap_name_t *zn,
    738     uint64_t integer_size, uint64_t num_integers, void *buf,
    739     char *realname, int rn_len, boolean_t *ncp)
    740 {
    741 	zap_leaf_t *l;
    742 	int err;
    743 	zap_entry_handle_t zeh;
    744 
    745 	err = fzap_checksize(zn, integer_size, num_integers);
    746 	if (err != 0)
    747 		return (err);
    748 
    749 	err = zap_deref_leaf(zn->zn_zap, zn->zn_hash, NULL, RW_READER, &l);
    750 	if (err != 0)
    751 		return (err);
    752 	err = zap_leaf_lookup(l, zn, &zeh);
    753 	if (err == 0) {
    754 		err = zap_entry_read(&zeh, integer_size, num_integers, buf);
    755 		(void) zap_entry_read_name(zn->zn_zap, &zeh, rn_len, realname);
    756 		if (ncp) {
    757 			*ncp = zap_entry_normalization_conflict(&zeh,
    758 			    zn, NULL, zn->zn_zap);
    759 		}
    760 	}
    761 
    762 	zap_put_leaf(l);
    763 	return (err);
    764 }
    765 
    766 int
    767 fzap_add_cd(zap_name_t *zn,
    768     uint64_t integer_size, uint64_t num_integers,
    769     const void *val, uint32_t cd, dmu_tx_t *tx)
    770 {
    771 	zap_leaf_t *l;
    772 	int err;
    773 	zap_entry_handle_t zeh;
    774 	zap_t *zap = zn->zn_zap;
    775 
    776 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    777 	ASSERT(!zap->zap_ismicro);
    778 	ASSERT(fzap_checksize(zn, integer_size, num_integers) == 0);
    779 
    780 	err = zap_deref_leaf(zap, zn->zn_hash, tx, RW_WRITER, &l);
    781 	if (err != 0)
    782 		return (err);
    783 retry:
    784 	err = zap_leaf_lookup(l, zn, &zeh);
    785 	if (err == 0) {
    786 		err = EEXIST;
    787 		goto out;
    788 	}
    789 	if (err != ENOENT)
    790 		goto out;
    791 
    792 	err = zap_entry_create(l, zn, cd,
    793 	    integer_size, num_integers, val, &zeh);
    794 
    795 	if (err == 0) {
    796 		zap_increment_num_entries(zap, 1, tx);
    797 	} else if (err == EAGAIN) {
    798 		err = zap_expand_leaf(zn, l, tx, &l);
    799 		zap = zn->zn_zap;	/* zap_expand_leaf() may change zap */
    800 		if (err == 0)
    801 			goto retry;
    802 	}
    803 
    804 out:
    805 	if (zap != NULL)
    806 		zap_put_leaf_maybe_grow_ptrtbl(zn, l, tx);
    807 	return (err);
    808 }
    809 
    810 int
    811 fzap_add(zap_name_t *zn,
    812     uint64_t integer_size, uint64_t num_integers,
    813     const void *val, dmu_tx_t *tx)
    814 {
    815 	int err = fzap_checksize(zn, integer_size, num_integers);
    816 	if (err != 0)
    817 		return (err);
    818 
    819 	return (fzap_add_cd(zn, integer_size, num_integers,
    820 	    val, ZAP_NEED_CD, tx));
    821 }
    822 
    823 int
    824 fzap_update(zap_name_t *zn,
    825     int integer_size, uint64_t num_integers, const void *val, dmu_tx_t *tx)
    826 {
    827 	zap_leaf_t *l;
    828 	int err, create;
    829 	zap_entry_handle_t zeh;
    830 	zap_t *zap = zn->zn_zap;
    831 
    832 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
    833 	err = fzap_checksize(zn, integer_size, num_integers);
    834 	if (err != 0)
    835 		return (err);
    836 
    837 	err = zap_deref_leaf(zap, zn->zn_hash, tx, RW_WRITER, &l);
    838 	if (err != 0)
    839 		return (err);
    840 retry:
    841 	err = zap_leaf_lookup(l, zn, &zeh);
    842 	create = (err == ENOENT);
    843 	ASSERT(err == 0 || err == ENOENT);
    844 
    845 	if (create) {
    846 		err = zap_entry_create(l, zn, ZAP_NEED_CD,
    847 		    integer_size, num_integers, val, &zeh);
    848 		if (err == 0)
    849 			zap_increment_num_entries(zap, 1, tx);
    850 	} else {
    851 		err = zap_entry_update(&zeh, integer_size, num_integers, val);
    852 	}
    853 
    854 	if (err == EAGAIN) {
    855 		err = zap_expand_leaf(zn, l, tx, &l);
    856 		zap = zn->zn_zap;	/* zap_expand_leaf() may change zap */
    857 		if (err == 0)
    858 			goto retry;
    859 	}
    860 
    861 	if (zap != NULL)
    862 		zap_put_leaf_maybe_grow_ptrtbl(zn, l, tx);
    863 	return (err);
    864 }
    865 
    866 int
    867 fzap_length(zap_name_t *zn,
    868     uint64_t *integer_size, uint64_t *num_integers)
    869 {
    870 	zap_leaf_t *l;
    871 	int err;
    872 	zap_entry_handle_t zeh;
    873 
    874 	err = zap_deref_leaf(zn->zn_zap, zn->zn_hash, NULL, RW_READER, &l);
    875 	if (err != 0)
    876 		return (err);
    877 	err = zap_leaf_lookup(l, zn, &zeh);
    878 	if (err != 0)
    879 		goto out;
    880 
    881 	if (integer_size)
    882 		*integer_size = zeh.zeh_integer_size;
    883 	if (num_integers)
    884 		*num_integers = zeh.zeh_num_integers;
    885 out:
    886 	zap_put_leaf(l);
    887 	return (err);
    888 }
    889 
    890 int
    891 fzap_remove(zap_name_t *zn, dmu_tx_t *tx)
    892 {
    893 	zap_leaf_t *l;
    894 	int err;
    895 	zap_entry_handle_t zeh;
    896 
    897 	err = zap_deref_leaf(zn->zn_zap, zn->zn_hash, tx, RW_WRITER, &l);
    898 	if (err != 0)
    899 		return (err);
    900 	err = zap_leaf_lookup(l, zn, &zeh);
    901 	if (err == 0) {
    902 		zap_entry_remove(&zeh);
    903 		zap_increment_num_entries(zn->zn_zap, -1, tx);
    904 	}
    905 	zap_put_leaf(l);
    906 	return (err);
    907 }
    908 
    909 /*
    910  * Helper functions for consumers.
    911  */
    912 
    913 int
    914 zap_value_search(objset_t *os, uint64_t zapobj, uint64_t value, uint64_t mask,
    915     char *name)
    916 {
    917 	zap_cursor_t zc;
    918 	zap_attribute_t *za;
    919 	int err;
    920 
    921 	if (mask == 0)
    922 		mask = -1ULL;
    923 
    924 	za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
    925 	for (zap_cursor_init(&zc, os, zapobj);
    926 	    (err = zap_cursor_retrieve(&zc, za)) == 0;
    927 	    zap_cursor_advance(&zc)) {
    928 		if ((za->za_first_integer & mask) == (value & mask)) {
    929 			(void) strcpy(name, za->za_name);
    930 			break;
    931 		}
    932 	}
    933 	zap_cursor_fini(&zc);
    934 	kmem_free(za, sizeof (zap_attribute_t));
    935 	return (err);
    936 }
    937 
    938 int
    939 zap_join(objset_t *os, uint64_t fromobj, uint64_t intoobj, dmu_tx_t *tx)
    940 {
    941 	zap_cursor_t zc;
    942 	zap_attribute_t za;
    943 	int err;
    944 
    945 	for (zap_cursor_init(&zc, os, fromobj);
    946 	    zap_cursor_retrieve(&zc, &za) == 0;
    947 	    (void) zap_cursor_advance(&zc)) {
    948 		if (za.za_integer_length != 8 || za.za_num_integers != 1)
    949 			return (EINVAL);
    950 		err = zap_add(os, intoobj, za.za_name,
    951 		    8, 1, &za.za_first_integer, tx);
    952 		if (err)
    953 			return (err);
    954 	}
    955 	zap_cursor_fini(&zc);
    956 	return (0);
    957 }
    958 
    959 int
    960 zap_add_int(objset_t *os, uint64_t obj, uint64_t value, dmu_tx_t *tx)
    961 {
    962 	char name[20];
    963 
    964 	(void) snprintf(name, sizeof (name), "%llx", (longlong_t)value);
    965 	return (zap_add(os, obj, name, 8, 1, &value, tx));
    966 }
    967 
    968 int
    969 zap_remove_int(objset_t *os, uint64_t obj, uint64_t value, dmu_tx_t *tx)
    970 {
    971 	char name[20];
    972 
    973 	(void) snprintf(name, sizeof (name), "%llx", (longlong_t)value);
    974 	return (zap_remove(os, obj, name, tx));
    975 }
    976 
    977 int
    978 zap_lookup_int(objset_t *os, uint64_t obj, uint64_t value)
    979 {
    980 	char name[20];
    981 
    982 	(void) snprintf(name, sizeof (name), "%llx", (longlong_t)value);
    983 	return (zap_lookup(os, obj, name, 8, 1, &value));
    984 }
    985 
    986 int
    987 zap_increment_int(objset_t *os, uint64_t obj, uint64_t key, int64_t delta,
    988     dmu_tx_t *tx)
    989 {
    990 	char name[20];
    991 	uint64_t value = 0;
    992 	int err;
    993 
    994 	if (delta == 0)
    995 		return (0);
    996 
    997 	(void) snprintf(name, sizeof (name), "%llx", (longlong_t)key);
    998 	err = zap_lookup(os, obj, name, 8, 1, &value);
    999 	if (err != 0 && err != ENOENT)
   1000 		return (err);
   1001 	value += delta;
   1002 	if (value == 0)
   1003 		err = zap_remove(os, obj, name, tx);
   1004 	else
   1005 		err = zap_update(os, obj, name, 8, 1, &value, tx);
   1006 	return (err);
   1007 }
   1008 
   1009 
   1010 /*
   1011  * Routines for iterating over the attributes.
   1012  */
   1013 
   1014 int
   1015 fzap_cursor_retrieve(zap_t *zap, zap_cursor_t *zc, zap_attribute_t *za)
   1016 {
   1017 	int err = ENOENT;
   1018 	zap_entry_handle_t zeh;
   1019 	zap_leaf_t *l;
   1020 
   1021 	/* memset(za, 0xba, sizeof (zap_attribute_t)); */
   1022 
   1023 	/* retrieve the next entry at or after zc_hash/zc_cd */
   1024 	/* if no entry, return ENOENT */
   1025 
   1026 	if (zc->zc_leaf &&
   1027 	    (ZAP_HASH_IDX(zc->zc_hash,
   1028 	    zc->zc_leaf->l_phys->l_hdr.lh_prefix_len) !=
   1029 	    zc->zc_leaf->l_phys->l_hdr.lh_prefix)) {
   1030 		rw_enter(&zc->zc_leaf->l_rwlock, RW_READER);
   1031 		zap_put_leaf(zc->zc_leaf);
   1032 		zc->zc_leaf = NULL;
   1033 	}
   1034 
   1035 again:
   1036 	if (zc->zc_leaf == NULL) {
   1037 		err = zap_deref_leaf(zap, zc->zc_hash, NULL, RW_READER,
   1038 		    &zc->zc_leaf);
   1039 		if (err != 0)
   1040 			return (err);
   1041 	} else {
   1042 		rw_enter(&zc->zc_leaf->l_rwlock, RW_READER);
   1043 	}
   1044 	l = zc->zc_leaf;
   1045 
   1046 	err = zap_leaf_lookup_closest(l, zc->zc_hash, zc->zc_cd, &zeh);
   1047 
   1048 	if (err == ENOENT) {
   1049 		uint64_t nocare =
   1050 		    (1ULL << (64 - l->l_phys->l_hdr.lh_prefix_len)) - 1;
   1051 		zc->zc_hash = (zc->zc_hash & ~nocare) + nocare + 1;
   1052 		zc->zc_cd = 0;
   1053 		if (l->l_phys->l_hdr.lh_prefix_len == 0 || zc->zc_hash == 0) {
   1054 			zc->zc_hash = -1ULL;
   1055 		} else {
   1056 			zap_put_leaf(zc->zc_leaf);
   1057 			zc->zc_leaf = NULL;
   1058 			goto again;
   1059 		}
   1060 	}
   1061 
   1062 	if (err == 0) {
   1063 		zc->zc_hash = zeh.zeh_hash;
   1064 		zc->zc_cd = zeh.zeh_cd;
   1065 		za->za_integer_length = zeh.zeh_integer_size;
   1066 		za->za_num_integers = zeh.zeh_num_integers;
   1067 		if (zeh.zeh_num_integers == 0) {
   1068 			za->za_first_integer = 0;
   1069 		} else {
   1070 			err = zap_entry_read(&zeh, 8, 1, &za->za_first_integer);
   1071 			ASSERT(err == 0 || err == EOVERFLOW);
   1072 		}
   1073 		err = zap_entry_read_name(zap, &zeh,
   1074 		    sizeof (za->za_name), za->za_name);
   1075 		ASSERT(err == 0);
   1076 
   1077 		za->za_normalization_conflict =
   1078 		    zap_entry_normalization_conflict(&zeh,
   1079 		    NULL, za->za_name, zap);
   1080 	}
   1081 	rw_exit(&zc->zc_leaf->l_rwlock);
   1082 	return (err);
   1083 }
   1084 
   1085 
   1086 static void
   1087 zap_stats_ptrtbl(zap_t *zap, uint64_t *tbl, int len, zap_stats_t *zs)
   1088 {
   1089 	int i, err;
   1090 	uint64_t lastblk = 0;
   1091 
   1092 	/*
   1093 	 * NB: if a leaf has more pointers than an entire ptrtbl block
   1094 	 * can hold, then it'll be accounted for more than once, since
   1095 	 * we won't have lastblk.
   1096 	 */
   1097 	for (i = 0; i < len; i++) {
   1098 		zap_leaf_t *l;
   1099 
   1100 		if (tbl[i] == lastblk)
   1101 			continue;
   1102 		lastblk = tbl[i];
   1103 
   1104 		err = zap_get_leaf_byblk(zap, tbl[i], NULL, RW_READER, &l);
   1105 		if (err == 0) {
   1106 			zap_leaf_stats(zap, l, zs);
   1107 			zap_put_leaf(l);
   1108 		}
   1109 	}
   1110 }
   1111 
   1112 int
   1113 fzap_cursor_move_to_key(zap_cursor_t *zc, zap_name_t *zn)
   1114 {
   1115 	int err;
   1116 	zap_leaf_t *l;
   1117 	zap_entry_handle_t zeh;
   1118 
   1119 	if (zn->zn_key_orig_len > ZAP_MAXNAMELEN)
   1120 		return (E2BIG);
   1121 
   1122 	err = zap_deref_leaf(zc->zc_zap, zn->zn_hash, NULL, RW_READER, &l);
   1123 	if (err != 0)
   1124 		return (err);
   1125 
   1126 	err = zap_leaf_lookup(l, zn, &zeh);
   1127 	if (err != 0)
   1128 		return (err);
   1129 
   1130 	zc->zc_leaf = l;
   1131 	zc->zc_hash = zeh.zeh_hash;
   1132 	zc->zc_cd = zeh.zeh_cd;
   1133 
   1134 	return (err);
   1135 }
   1136 
   1137 void
   1138 fzap_get_stats(zap_t *zap, zap_stats_t *zs)
   1139 {
   1140 	int bs = FZAP_BLOCK_SHIFT(zap);
   1141 	zs->zs_blocksize = 1ULL << bs;
   1142 
   1143 	/*
   1144 	 * Set zap_phys_t fields
   1145 	 */
   1146 	zs->zs_num_leafs = zap->zap_f.zap_phys->zap_num_leafs;
   1147 	zs->zs_num_entries = zap->zap_f.zap_phys->zap_num_entries;
   1148 	zs->zs_num_blocks = zap->zap_f.zap_phys->zap_freeblk;
   1149 	zs->zs_block_type = zap->zap_f.zap_phys->zap_block_type;
   1150 	zs->zs_magic = zap->zap_f.zap_phys->zap_magic;
   1151 	zs->zs_salt = zap->zap_f.zap_phys->zap_salt;
   1152 
   1153 	/*
   1154 	 * Set zap_ptrtbl fields
   1155 	 */
   1156 	zs->zs_ptrtbl_len = 1ULL << zap->zap_f.zap_phys->zap_ptrtbl.zt_shift;
   1157 	zs->zs_ptrtbl_nextblk = zap->zap_f.zap_phys->zap_ptrtbl.zt_nextblk;
   1158 	zs->zs_ptrtbl_blks_copied =
   1159 	    zap->zap_f.zap_phys->zap_ptrtbl.zt_blks_copied;
   1160 	zs->zs_ptrtbl_zt_blk = zap->zap_f.zap_phys->zap_ptrtbl.zt_blk;
   1161 	zs->zs_ptrtbl_zt_numblks = zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks;
   1162 	zs->zs_ptrtbl_zt_shift = zap->zap_f.zap_phys->zap_ptrtbl.zt_shift;
   1163 
   1164 	if (zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks == 0) {
   1165 		/* the ptrtbl is entirely in the header block. */
   1166 		zap_stats_ptrtbl(zap, &ZAP_EMBEDDED_PTRTBL_ENT(zap, 0),
   1167 		    1 << ZAP_EMBEDDED_PTRTBL_SHIFT(zap), zs);
   1168 	} else {
   1169 		int b;
   1170 
   1171 		dmu_prefetch(zap->zap_objset, zap->zap_object,
   1172 		    zap->zap_f.zap_phys->zap_ptrtbl.zt_blk << bs,
   1173 		    zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks << bs);
   1174 
   1175 		for (b = 0; b < zap->zap_f.zap_phys->zap_ptrtbl.zt_numblks;
   1176 		    b++) {
   1177 			dmu_buf_t *db;
   1178 			int err;
   1179 
   1180 			err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
   1181 			    (zap->zap_f.zap_phys->zap_ptrtbl.zt_blk + b) << bs,
   1182 			    FTAG, &db);
   1183 			if (err == 0) {
   1184 				zap_stats_ptrtbl(zap, db->db_data,
   1185 				    1<<(bs-3), zs);
   1186 				dmu_buf_rele(db, FTAG);
   1187 			}
   1188 		}
   1189 	}
   1190 }
   1191 
   1192 int
   1193 fzap_count_write(zap_name_t *zn, int add, uint64_t *towrite,
   1194     uint64_t *tooverwrite)
   1195 {
   1196 	zap_t *zap = zn->zn_zap;
   1197 	zap_leaf_t *l;
   1198 	int err;
   1199 
   1200 	/*
   1201 	 * Account for the header block of the fatzap.
   1202 	 */
   1203 	if (!add && dmu_buf_freeable(zap->zap_dbuf)) {
   1204 		*tooverwrite += zap->zap_dbuf->db_size;
   1205 	} else {
   1206 		*towrite += zap->zap_dbuf->db_size;
   1207 	}
   1208 
   1209 	/*
   1210 	 * Account for the pointer table blocks.
   1211 	 * If we are adding we need to account for the following cases :
   1212 	 * - If the pointer table is embedded, this operation could force an
   1213 	 *   external pointer table.
   1214 	 * - If this already has an external pointer table this operation
   1215 	 *   could extend the table.
   1216 	 */
   1217 	if (add) {
   1218 		if (zap->zap_f.zap_phys->zap_ptrtbl.zt_blk == 0)
   1219 			*towrite += zap->zap_dbuf->db_size;
   1220 		else
   1221 			*towrite += (zap->zap_dbuf->db_size * 3);
   1222 	}
   1223 
   1224 	/*
   1225 	 * Now, check if the block containing leaf is freeable
   1226 	 * and account accordingly.
   1227 	 */
   1228 	err = zap_deref_leaf(zap, zn->zn_hash, NULL, RW_READER, &l);
   1229 	if (err != 0) {
   1230 		return (err);
   1231 	}
   1232 
   1233 	if (!add && dmu_buf_freeable(l->l_dbuf)) {
   1234 		*tooverwrite += l->l_dbuf->db_size;
   1235 	} else {
   1236 		/*
   1237 		 * If this an add operation, the leaf block could split.
   1238 		 * Hence, we need to account for an additional leaf block.
   1239 		 */
   1240 		*towrite += (add ? 2 : 1) * l->l_dbuf->db_size;
   1241 	}
   1242 
   1243 	zap_put_leaf(l);
   1244 	return (0);
   1245 }
   1246