9328 zap code can take advantage of c99

9329 panic in zap_leaf_lookup() due to concurrent zapification
Reviewed by: Steve Gonczi <steve.gonczi@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>

4 files changed, 258 insertions, 350 deletions

diff --git a/usr/src/uts/common/fs/zfs/dmu_object.c b/usr/src/uts/common/fs/zfs/dmu_object.c
index 40898ef26d..9f0f2b437c 100644
--- a/usr/src/uts/common/fs/zfs/dmu_object.c
+++ b/usr/src/uts/common/fs/zfs/dmu_object.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2013, 2017 by Delphix. All rights reserved.
  * Copyright 2014 HybridCluster. All rights reserved.
  */
 
@@ -204,13 +204,19 @@ dmu_object_zapify(objset_t *mos, uint64_t object, dmu_object_type_t old_type,
 	}
 	ASSERT3U(dn->dn_type, ==, old_type);
 	ASSERT0(dn->dn_maxblkid);
+
+	/*
+	 * We must initialize the ZAP data before changing the type,
+	 * so that concurrent calls to *_is_zapified() can determine if
+	 * the object has been completely zapified by checking the type.
+	 */
+	mzap_create_impl(mos, object, 0, 0, tx);
+
 	dn->dn_next_type[tx->tx_txg & TXG_MASK] = dn->dn_type =
 	    DMU_OTN_ZAP_METADATA;
 	dnode_setdirty(dn, tx);
 	dnode_rele(dn, FTAG);
 
-	mzap_create_impl(mos, object, 0, 0, tx);
-
 	spa_feature_incr(dmu_objset_spa(mos),
 	    SPA_FEATURE_EXTENSIBLE_DATASET, tx);
 }
diff --git a/usr/src/uts/common/fs/zfs/zap.c b/usr/src/uts/common/fs/zfs/zap.c
index 70bf9d12db..e9ed41e556 100644
--- a/usr/src/uts/common/fs/zfs/zap.c
+++ b/usr/src/uts/common/fs/zfs/zap.c
@@ -58,9 +58,7 @@ 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;
+	uint64_t block_type = *(uint64_t *)vbuf;
 
 	if (block_type == ZBT_LEAF || block_type == BSWAP_64(ZBT_LEAF))
 		zap_leaf_byteswap(vbuf, size);
@@ -73,11 +71,6 @@ fzap_byteswap(void *vbuf, size_t size)
 void
 fzap_upgrade(zap_t *zap, dmu_tx_t *tx, zap_flags_t flags)
 {
-	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;
 
@@ -87,7 +80,7 @@ fzap_upgrade(zap_t *zap, dmu_tx_t *tx, zap_flags_t flags)
 	mutex_init(&zap->zap_f.zap_num_entries_mtx, 0, 0, 0);
 	zap->zap_f.zap_block_shift = highbit64(zap->zap_dbuf->db_size) - 1;
 
-	zp = zap_f_phys(zap);
+	zap_phys_t *zp = zap_f_phys(zap);
 	/*
 	 * explicitly zero it since it might be coming from an
 	 * initialized microzap
@@ -106,17 +99,18 @@ fzap_upgrade(zap_t *zap, dmu_tx_t *tx, zap_flags_t flags)
 	zp->zap_flags = flags;
 
 	/* block 1 will be the first leaf */
-	for (i = 0; i < (1<<zp->zap_ptrtbl.zt_shift); i++)
+	for (int 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,
+	dmu_buf_t *db;
+	VERIFY0(dmu_buf_hold(zap->zap_objset, zap->zap_object,
 	    1<<FZAP_BLOCK_SHIFT(zap), FTAG, &db, DMU_READ_NO_PREFETCH));
 	dmu_buf_will_dirty(db, tx);
 
-	l = kmem_zalloc(sizeof (zap_leaf_t), KM_SLEEP);
+	zap_leaf_t *l = kmem_zalloc(sizeof (zap_leaf_t), KM_SLEEP);
 	l->l_dbuf = db;
 
 	zap_leaf_init(l, zp->zap_normflags != 0);
@@ -146,9 +140,7 @@ 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;
+	uint64_t newblk;
 	int bs = FZAP_BLOCK_SHIFT(zap);
 	int hepb = 1<<(bs-4);
 	/* hepb = half the number of entries in a block */
@@ -172,21 +164,23 @@ zap_table_grow(zap_t *zap, zap_table_phys_t *tbl,
 	 * Copy the ptrtbl from the old to new location.
 	 */
 
-	b = tbl->zt_blks_copied;
-	err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
+	uint64_t b = tbl->zt_blks_copied;
+	dmu_buf_t *db_old;
+	int err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
 	    (tbl->zt_blk + b) << bs, FTAG, &db_old, DMU_READ_NO_PREFETCH);
-	if (err)
+	if (err != 0)
 		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,
+	dmu_buf_t *db_new;
+	VERIFY0(dmu_buf_hold(zap->zap_objset, zap->zap_object,
 	    (newblk + 2*b+0) << bs, FTAG, &db_new, DMU_READ_NO_PREFETCH));
 	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,
+	VERIFY0(dmu_buf_hold(zap->zap_objset, zap->zap_object,
 	    (newblk + 2*b+1) << bs, FTAG, &db_new, DMU_READ_NO_PREFETCH));
 	dmu_buf_will_dirty(db_new, tx);
 	transfer_func((uint64_t *)db_old->db_data + hepb,
@@ -221,22 +215,20 @@ 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);
+	uint64_t blk = idx >> (bs-3);
+	uint64_t off = idx & ((1<<(bs-3))-1);
 
-	err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
+	dmu_buf_t *db;
+	int err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
 	    (tbl->zt_blk + blk) << bs, FTAG, &db, DMU_READ_NO_PREFETCH);
-	if (err)
+	if (err != 0)
 		return (err);
 	dmu_buf_will_dirty(db, tx);
 
@@ -249,7 +241,7 @@ zap_table_store(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t val,
 		err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
 		    (tbl->zt_nextblk + blk2) << bs, FTAG, &db2,
 		    DMU_READ_NO_PREFETCH);
-		if (err) {
+		if (err != 0) {
 			dmu_buf_rele(db, FTAG);
 			return (err);
 		}
@@ -268,27 +260,24 @@ zap_table_store(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t val,
 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;
-	dnode_t *dn;
 	int bs = FZAP_BLOCK_SHIFT(zap);
 
 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
 
-	blk = idx >> (bs-3);
-	off = idx & ((1<<(bs-3))-1);
+	uint64_t blk = idx >> (bs-3);
+	uint64_t off = idx & ((1<<(bs-3))-1);
 
 	/*
 	 * Note: this is equivalent to dmu_buf_hold(), but we use
 	 * _dnode_enter / _by_dnode because it's faster because we don't
 	 * have to hold the dnode.
 	 */
-	dn = dmu_buf_dnode_enter(zap->zap_dbuf);
-	err = dmu_buf_hold_by_dnode(dn,
+	dnode_t *dn = dmu_buf_dnode_enter(zap->zap_dbuf);
+	dmu_buf_t *db;
+	int err = dmu_buf_hold_by_dnode(dn,
 	    (tbl->zt_blk + blk) << bs, FTAG, &db, DMU_READ_NO_PREFETCH);
 	dmu_buf_dnode_exit(zap->zap_dbuf);
-	if (err)
+	if (err != 0)
 		return (err);
 	*valp = ((uint64_t *)db->db_data)[off];
 	dmu_buf_rele(db, FTAG);
@@ -319,11 +308,10 @@ zap_table_load(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t *valp)
 static void
 zap_ptrtbl_transfer(const uint64_t *src, uint64_t *dst, int n)
 {
-	int i;
-	for (i = 0; i < n; i++) {
+	for (int i = 0; i < n; i++) {
 		uint64_t lb = src[i];
-		dst[2*i+0] = lb;
-		dst[2*i+1] = lb;
+		dst[2 * i + 0] = lb;
+		dst[2 * i + 1] = lb;
 	}
 }
 
@@ -345,19 +333,16 @@ zap_grow_ptrtbl(zap_t *zap, dmu_tx_t *tx)
 		 * 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_f_phys(zap)->zap_ptrtbl.zt_shift, ==,
 		    ZAP_EMBEDDED_PTRTBL_SHIFT(zap));
 		ASSERT0(zap_f_phys(zap)->zap_ptrtbl.zt_blk);
 
-		newblk = zap_allocate_blocks(zap, 1);
-		err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
+		uint64_t newblk = zap_allocate_blocks(zap, 1);
+		dmu_buf_t *db_new;
+		int err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
 		    newblk << FZAP_BLOCK_SHIFT(zap), FTAG, &db_new,
 		    DMU_READ_NO_PREFETCH);
-		if (err)
+		if (err != 0)
 			return (err);
 		dmu_buf_will_dirty(db_new, tx);
 		zap_ptrtbl_transfer(&ZAP_EMBEDDED_PTRTBL_ENT(zap, 0),
@@ -392,9 +377,8 @@ zap_increment_num_entries(zap_t *zap, int delta, dmu_tx_t *tx)
 static uint64_t
 zap_allocate_blocks(zap_t *zap, int nblocks)
 {
-	uint64_t newblk;
 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
-	newblk = zap_f_phys(zap)->zap_freeblk;
+	uint64_t newblk = zap_f_phys(zap)->zap_freeblk;
 	zap_f_phys(zap)->zap_freeblk += nblocks;
 	return (newblk);
 }
@@ -411,7 +395,6 @@ zap_leaf_evict_sync(void *dbu)
 static zap_leaf_t *
 zap_create_leaf(zap_t *zap, dmu_tx_t *tx)
 {
-	void *winner;
 	zap_leaf_t *l = kmem_zalloc(sizeof (zap_leaf_t), KM_SLEEP);
 
 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
@@ -421,12 +404,11 @@ zap_create_leaf(zap_t *zap, dmu_tx_t *tx)
 	l->l_blkid = zap_allocate_blocks(zap, 1);
 	l->l_dbuf = NULL;
 
-	VERIFY(0 == dmu_buf_hold(zap->zap_objset, zap->zap_object,
+	VERIFY0(dmu_buf_hold(zap->zap_objset, zap->zap_object,
 	    l->l_blkid << FZAP_BLOCK_SHIFT(zap), NULL, &l->l_dbuf,
 	    DMU_READ_NO_PREFETCH));
 	dmu_buf_init_user(&l->l_dbu, zap_leaf_evict_sync, NULL, &l->l_dbuf);
-	winner = dmu_buf_set_user(l->l_dbuf, &l->l_dbu);
-	ASSERT(winner == NULL);
+	VERIFY3P(NULL, ==, dmu_buf_set_user(l->l_dbuf, &l->l_dbu));
 	dmu_buf_will_dirty(l->l_dbuf, tx);
 
 	zap_leaf_init(l, zap->zap_normflags != 0);
@@ -460,11 +442,9 @@ zap_put_leaf(zap_leaf_t *l)
 static zap_leaf_t *
 zap_open_leaf(uint64_t blkid, dmu_buf_t *db)
 {
-	zap_leaf_t *l, *winner;
-
 	ASSERT(blkid != 0);
 
-	l = kmem_zalloc(sizeof (zap_leaf_t), KM_SLEEP);
+	zap_leaf_t *l = kmem_zalloc(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;
@@ -472,7 +452,7 @@ zap_open_leaf(uint64_t blkid, dmu_buf_t *db)
 	l->l_dbuf = db;
 
 	dmu_buf_init_user(&l->l_dbu, zap_leaf_evict_sync, NULL, &l->l_dbuf);
-	winner = dmu_buf_set_user(db, &l->l_dbu);
+	zap_leaf_t *winner = dmu_buf_set_user(db, &l->l_dbu);
 
 	rw_exit(&l->l_rwlock);
 	if (winner != NULL) {
@@ -510,17 +490,15 @@ 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));
 
+	int bs = FZAP_BLOCK_SHIFT(zap);
 	dnode_t *dn = dmu_buf_dnode_enter(zap->zap_dbuf);
-	err = dmu_buf_hold_by_dnode(dn,
+	int err = dmu_buf_hold_by_dnode(dn,
 	    blkid << bs, NULL, &db, DMU_READ_NO_PREFETCH);
 	dmu_buf_dnode_exit(zap->zap_dbuf);
-	if (err)
+	if (err != 0)
 		return (err);
 
 	ASSERT3U(db->db_object, ==, zap->zap_object);
@@ -528,7 +506,7 @@ zap_get_leaf_byblk(zap_t *zap, uint64_t blkid, dmu_tx_t *tx, krw_t lt,
 	ASSERT3U(db->db_size, ==, 1 << bs);
 	ASSERT(blkid != 0);
 
-	l = dmu_buf_get_user(db);
+	zap_leaf_t *l = dmu_buf_get_user(db);
 
 	if (l == NULL)
 		l = zap_open_leaf(blkid, db);
@@ -583,8 +561,7 @@ zap_set_idx_to_blk(zap_t *zap, uint64_t idx, uint64_t blk, dmu_tx_t *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;
+	uint64_t blk;
 
 	ASSERT(zap->zap_dbuf == NULL ||
 	    zap_f_phys(zap) == zap->zap_dbuf->db_data);
@@ -596,8 +573,8 @@ zap_deref_leaf(zap_t *zap, uint64_t h, dmu_tx_t *tx, krw_t lt, zap_leaf_t **lp)
 		return (SET_ERROR(EIO));
 	}
 
-	idx = ZAP_HASH_IDX(h, zap_f_phys(zap)->zap_ptrtbl.zt_shift);
-	err = zap_idx_to_blk(zap, idx, &blk);
+	uint64_t idx = ZAP_HASH_IDX(h, zap_f_phys(zap)->zap_ptrtbl.zt_shift);
+	int err = zap_idx_to_blk(zap, idx, &blk);
 	if (err != 0)
 		return (err);
 	err = zap_get_leaf_byblk(zap, blk, tx, lt, lp);
@@ -614,9 +591,7 @@ zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l,
 {
 	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 err;
 	int old_prefix_len = zap_leaf_phys(l)->l_hdr.lh_prefix_len;
 
 	ASSERT3U(old_prefix_len, <=, zap_f_phys(zap)->zap_ptrtbl.zt_shift);
@@ -636,19 +611,19 @@ zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l,
 		err = zap_lockdir(os, object, tx, RW_WRITER,
 		    FALSE, FALSE, tag, &zn->zn_zap);
 		zap = zn->zn_zap;
-		if (err)
+		if (err != 0)
 			return (err);
 		ASSERT(!zap->zap_ismicro);
 
 		while (old_prefix_len ==
 		    zap_f_phys(zap)->zap_ptrtbl.zt_shift) {
 			err = zap_grow_ptrtbl(zap, tx);
-			if (err)
+			if (err != 0)
 				return (err);
 		}
 
 		err = zap_deref_leaf(zap, hash, tx, RW_WRITER, &l);
-		if (err)
+		if (err != 0)
 			return (err);
 
 		if (zap_leaf_phys(l)->l_hdr.lh_prefix_len != old_prefix_len) {
@@ -662,25 +637,26 @@ zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l,
 	ASSERT3U(ZAP_HASH_IDX(hash, old_prefix_len), ==,
 	    zap_leaf_phys(l)->l_hdr.lh_prefix);
 
-	prefix_diff = zap_f_phys(zap)->zap_ptrtbl.zt_shift -
+	int prefix_diff = zap_f_phys(zap)->zap_ptrtbl.zt_shift -
 	    (old_prefix_len + 1);
-	sibling = (ZAP_HASH_IDX(hash, old_prefix_len + 1) | 1) << prefix_diff;
+	uint64_t 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++) {
+	for (int i = 0; i < (1ULL << prefix_diff); i++) {
 		uint64_t blk;
-		err = zap_idx_to_blk(zap, sibling+i, &blk);
-		if (err)
+		err = zap_idx_to_blk(zap, sibling + i, &blk);
+		if (err != 0)
 			return (err);
 		ASSERT3U(blk, ==, l->l_blkid);
 	}
 
-	nl = zap_create_leaf(zap, tx);
+	zap_leaf_t *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);
+	for (int i = 0; i < (1ULL << prefix_diff); i++) {
+		err = zap_set_idx_to_blk(zap, sibling + i, nl->l_blkid, tx);
 		ASSERT0(err); /* we checked for i/o errors above */
 	}
 
@@ -708,8 +684,6 @@ zap_put_leaf_maybe_grow_ptrtbl(zap_name_t *zn, zap_leaf_t *l,
 	zap_put_leaf(l);
 
 	if (leaffull || zap_f_phys(zap)->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.
@@ -719,10 +693,10 @@ zap_put_leaf_maybe_grow_ptrtbl(zap_name_t *zn, zap_leaf_t *l,
 			uint64_t zapobj = zap->zap_object;
 
 			zap_unlockdir(zap, tag);
-			err = zap_lockdir(os, zapobj, tx,
+			int err = zap_lockdir(os, zapobj, tx,
 			    RW_WRITER, FALSE, FALSE, tag, &zn->zn_zap);
 			zap = zn->zn_zap;
-			if (err)
+			if (err != 0)
 				return;
 		}
 
@@ -763,9 +737,8 @@ fzap_checksize(uint64_t integer_size, uint64_t num_integers)
 static int
 fzap_check(zap_name_t *zn, uint64_t integer_size, uint64_t num_integers)
 {
-	int err;
-
-	if ((err = fzap_checkname(zn)) != 0)
+	int err = fzap_checkname(zn);
+	if (err != 0)
 		return (err);
 	return (fzap_checksize(integer_size, num_integers));
 }
@@ -779,10 +752,10 @@ fzap_lookup(zap_name_t *zn,
     char *realname, int rn_len, boolean_t *ncp)
 {
 	zap_leaf_t *l;
-	int err;
 	zap_entry_handle_t zeh;
 
-	if ((err = fzap_checkname(zn)) != 0)
+	int err = fzap_checkname(zn);
+	if (err != 0)
 		return (err);
 
 	err = zap_deref_leaf(zn->zn_zap, zn->zn_hash, NULL, RW_READER, &l);
@@ -870,7 +843,8 @@ fzap_update(zap_name_t *zn,
     void *tag, dmu_tx_t *tx)
 {
 	zap_leaf_t *l;
-	int err, create;
+	int err;
+	boolean_t create;
 	zap_entry_handle_t zeh;
 	zap_t *zap = zn->zn_zap;
 
@@ -923,9 +897,9 @@ fzap_length(zap_name_t *zn,
 	if (err != 0)
 		goto out;
 
-	if (integer_size)
+	if (integer_size != 0)
 		*integer_size = zeh.zeh_integer_size;
-	if (num_integers)
+	if (num_integers != 0)
 		*num_integers = zeh.zeh_num_integers;
 out:
 	zap_put_leaf(l);
@@ -954,15 +928,14 @@ fzap_remove(zap_name_t *zn, dmu_tx_t *tx)
 void
 fzap_prefetch(zap_name_t *zn)
 {
-	uint64_t idx, blk;
+	uint64_t blk;
 	zap_t *zap = zn->zn_zap;
-	int bs;
 
-	idx = ZAP_HASH_IDX(zn->zn_hash,
+	uint64_t idx = ZAP_HASH_IDX(zn->zn_hash,
 	    zap_f_phys(zap)->zap_ptrtbl.zt_shift);
 	if (zap_idx_to_blk(zap, idx, &blk) != 0)
 		return;
-	bs = FZAP_BLOCK_SHIFT(zap);
+	int bs = FZAP_BLOCK_SHIFT(zap);
 	dmu_prefetch(zap->zap_objset, zap->zap_object, 0, blk << bs, 1 << bs,
 	    ZIO_PRIORITY_SYNC_READ);
 }
@@ -975,9 +948,8 @@ uint64_t
 zap_create_link(objset_t *os, dmu_object_type_t ot, uint64_t parent_obj,
     const char *name, dmu_tx_t *tx)
 {
-	uint64_t new_obj;
-
-	VERIFY((new_obj = zap_create(os, ot, DMU_OT_NONE, 0, tx)) > 0);
+	uint64_t new_obj = zap_create(os, ot, DMU_OT_NONE, 0, tx);
+	VERIFY(new_obj != 0);
 	VERIFY0(zap_add(os, parent_obj, name, sizeof (uint64_t), 1, &new_obj,
 	    tx));
 
@@ -989,13 +961,12 @@ 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);
+	zap_attribute_t *za = kmem_alloc(sizeof (*za), KM_SLEEP);
 	for (zap_cursor_init(&zc, os, zapobj);
 	    (err = zap_cursor_retrieve(&zc, za)) == 0;
 	    zap_cursor_advance(&zc)) {
@@ -1005,7 +976,7 @@ zap_value_search(objset_t *os, uint64_t zapobj, uint64_t value, uint64_t mask,
 		}
 	}
 	zap_cursor_fini(&zc);
-	kmem_free(za, sizeof (zap_attribute_t));
+	kmem_free(za, sizeof (*za));
 	return (err);
 }
 
@@ -1013,23 +984,23 @@ 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;
+	int err = 0;
 
-	err = 0;
+	zap_attribute_t *za = kmem_alloc(sizeof (*za), KM_SLEEP);
 	for (zap_cursor_init(&zc, os, fromobj);
-	    zap_cursor_retrieve(&zc, &za) == 0;
+	    zap_cursor_retrieve(&zc, za) == 0;
 	    (void) zap_cursor_advance(&zc)) {
-		if (za.za_integer_length != 8 || za.za_num_integers != 1) {
+		if (za->za_integer_length != 8 || za->za_num_integers != 1) {
 			err = SET_ERROR(EINVAL);
 			break;
 		}
-		err = zap_add(os, intoobj, za.za_name,
-		    8, 1, &za.za_first_integer, tx);
-		if (err)
+		err = zap_add(os, intoobj, za->za_name,
+		    8, 1, &za->za_first_integer, tx);
+		if (err != 0)
 			break;
 	}
 	zap_cursor_fini(&zc);
+	kmem_free(za, sizeof (*za));
 	return (err);
 }
 
@@ -1038,23 +1009,23 @@ zap_join_key(objset_t *os, uint64_t fromobj, uint64_t intoobj,
     uint64_t value, dmu_tx_t *tx)
 {
 	zap_cursor_t zc;
-	zap_attribute_t za;
-	int err;
+	int err = 0;
 
-	err = 0;
+	zap_attribute_t *za = kmem_alloc(sizeof (*za), KM_SLEEP);
 	for (zap_cursor_init(&zc, os, fromobj);
-	    zap_cursor_retrieve(&zc, &za) == 0;
+	    zap_cursor_retrieve(&zc, za) == 0;
 	    (void) zap_cursor_advance(&zc)) {
-		if (za.za_integer_length != 8 || za.za_num_integers != 1) {
+		if (za->za_integer_length != 8 || za->za_num_integers != 1) {
 			err = SET_ERROR(EINVAL);
 			break;
 		}
-		err = zap_add(os, intoobj, za.za_name,
+		err = zap_add(os, intoobj, za->za_name,
 		    8, 1, &value, tx);
-		if (err)
+		if (err != 0)
 			break;
 	}
 	zap_cursor_fini(&zc);
+	kmem_free(za, sizeof (*za));
 	return (err);
 }
 
@@ -1063,29 +1034,29 @@ zap_join_increment(objset_t *os, uint64_t fromobj, uint64_t intoobj,
     dmu_tx_t *tx)
 {
 	zap_cursor_t zc;
-	zap_attribute_t za;
-	int err;
+	int err = 0;
 
-	err = 0;
+	zap_attribute_t *za = kmem_alloc(sizeof (*za), KM_SLEEP);
 	for (zap_cursor_init(&zc, os, fromobj);
-	    zap_cursor_retrieve(&zc, &za) == 0;
+	    zap_cursor_retrieve(&zc, za) == 0;
 	    (void) zap_cursor_advance(&zc)) {
 		uint64_t delta = 0;
 
-		if (za.za_integer_length != 8 || za.za_num_integers != 1) {
+		if (za->za_integer_length != 8 || za->za_num_integers != 1) {
 			err = SET_ERROR(EINVAL);
 			break;
 		}
 
-		err = zap_lookup(os, intoobj, za.za_name, 8, 1, &delta);
+		err = zap_lookup(os, intoobj, za->za_name, 8, 1, &delta);
 		if (err != 0 && err != ENOENT)
 			break;
-		delta += za.za_first_integer;
-		err = zap_update(os, intoobj, za.za_name, 8, 1, &delta, tx);
-		if (err)
+		delta += za->za_first_integer;
+		err = zap_update(os, intoobj, za->za_name, 8, 1, &delta, tx);
+		if (err != 0)
 			break;
 	}
 	zap_cursor_fini(&zc);
+	kmem_free(za, sizeof (*za));
 	return (err);
 }
 
@@ -1150,12 +1121,11 @@ zap_increment(objset_t *os, uint64_t obj, const char *name, int64_t delta,
     dmu_tx_t *tx)
 {
 	uint64_t value = 0;
-	int err;
 
 	if (delta == 0)
 		return (0);
 
-	err = zap_lookup(os, obj, name, 8, 1, &value);
+	int err = zap_lookup(os, obj, name, 8, 1, &value);
 	if (err != 0 && err != ENOENT)
 		return (err);
 	value += delta;
@@ -1253,7 +1223,6 @@ again:
 static void
 zap_stats_ptrtbl(zap_t *zap, uint64_t *tbl, int len, zap_stats_t *zs)
 {
-	int i, err;
 	uint64_t lastblk = 0;
 
 	/*
@@ -1261,14 +1230,14 @@ zap_stats_ptrtbl(zap_t *zap, uint64_t *tbl, int len, zap_stats_t *zs)
 	 * can hold, then it'll be accounted for more than once, since
 	 * we won't have lastblk.
 	 */
-	for (i = 0; i < len; i++) {
+	for (int 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);
+		int 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);
@@ -1308,14 +1277,12 @@ fzap_get_stats(zap_t *zap, zap_stats_t *zs)
 		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, 0,
 		    zap_f_phys(zap)->zap_ptrtbl.zt_blk << bs,
 		    zap_f_phys(zap)->zap_ptrtbl.zt_numblks << bs,
 		    ZIO_PRIORITY_SYNC_READ);
 
-		for (b = 0; b < zap_f_phys(zap)->zap_ptrtbl.zt_numblks;
+		for (int b = 0; b < zap_f_phys(zap)->zap_ptrtbl.zt_numblks;
 		    b++) {
 			dmu_buf_t *db;
 			int err;
diff --git a/usr/src/uts/common/fs/zfs/zap_leaf.c b/usr/src/uts/common/fs/zfs/zap_leaf.c
index 35dca89728..1c7c736d8e 100644
--- a/usr/src/uts/common/fs/zfs/zap_leaf.c
+++ b/usr/src/uts/common/fs/zfs/zap_leaf.c
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2013, 2016 by Delphix. All rights reserved.
  * Copyright 2017 Nexenta Systems, Inc.
  */
 
@@ -107,7 +107,6 @@ ldv(int len, const void *addr)
 void
 zap_leaf_byteswap(zap_leaf_phys_t *buf, int size)
 {
-	int i;
 	zap_leaf_t l;
 	dmu_buf_t l_dbuf;
 
@@ -123,10 +122,10 @@ zap_leaf_byteswap(zap_leaf_phys_t *buf, int size)
 	buf->l_hdr.lh_prefix_len =	BSWAP_16(buf->l_hdr.lh_prefix_len);
 	buf->l_hdr.lh_freelist =	BSWAP_16(buf->l_hdr.lh_freelist);
 
-	for (i = 0; i < ZAP_LEAF_HASH_NUMENTRIES(&l); i++)
+	for (int i = 0; i < ZAP_LEAF_HASH_NUMENTRIES(&l); i++)
 		buf->l_hash[i] = BSWAP_16(buf->l_hash[i]);
 
-	for (i = 0; i < ZAP_LEAF_NUMCHUNKS(&l); i++) {
+	for (int i = 0; i < ZAP_LEAF_NUMCHUNKS(&l); i++) {
 		zap_leaf_chunk_t *lc = &ZAP_LEAF_CHUNK(&l, i);
 		struct zap_leaf_entry *le;
 
@@ -162,14 +161,12 @@ zap_leaf_byteswap(zap_leaf_phys_t *buf, int size)
 void
 zap_leaf_init(zap_leaf_t *l, boolean_t sort)
 {
-	int i;
-
 	l->l_bs = highbit64(l->l_dbuf->db_size) - 1;
 	zap_memset(&zap_leaf_phys(l)->l_hdr, 0,
 	    sizeof (struct zap_leaf_header));
 	zap_memset(zap_leaf_phys(l)->l_hash, CHAIN_END,
 	    2*ZAP_LEAF_HASH_NUMENTRIES(l));
-	for (i = 0; i < ZAP_LEAF_NUMCHUNKS(l); i++) {
+	for (int i = 0; i < ZAP_LEAF_NUMCHUNKS(l); i++) {
 		ZAP_LEAF_CHUNK(l, i).l_free.lf_type = ZAP_CHUNK_FREE;
 		ZAP_LEAF_CHUNK(l, i).l_free.lf_next = i+1;
 	}
@@ -188,11 +185,9 @@ zap_leaf_init(zap_leaf_t *l, boolean_t sort)
 static uint16_t
 zap_leaf_chunk_alloc(zap_leaf_t *l)
 {
-	int chunk;
-
 	ASSERT(zap_leaf_phys(l)->l_hdr.lh_nfree > 0);
 
-	chunk = zap_leaf_phys(l)->l_hdr.lh_freelist;
+	int chunk = zap_leaf_phys(l)->l_hdr.lh_freelist;
 	ASSERT3U(chunk, <, ZAP_LEAF_NUMCHUNKS(l));
 	ASSERT3U(ZAP_LEAF_CHUNK(l, chunk).l_free.lf_type, ==, ZAP_CHUNK_FREE);
 
@@ -232,7 +227,7 @@ zap_leaf_array_create(zap_leaf_t *l, const char *buf,
 	uint16_t *chunkp = &chunk_head;
 	int byten = 0;
 	uint64_t value = 0;
-	int shift = (integer_size-1)*8;
+	int shift = (integer_size - 1) * 8;
 	int len = num_integers;
 
 	ASSERT3U(num_integers * integer_size, <, MAX_ARRAY_BYTES);
@@ -240,10 +235,9 @@ zap_leaf_array_create(zap_leaf_t *l, const char *buf,
 	while (len > 0) {
 		uint16_t chunk = zap_leaf_chunk_alloc(l);
 		struct zap_leaf_array *la = &ZAP_LEAF_CHUNK(l, chunk).l_array;
-		int i;
 
 		la->la_type = ZAP_CHUNK_ARRAY;
-		for (i = 0; i < ZAP_LEAF_ARRAY_BYTES; i++) {
+		for (int i = 0; i < ZAP_LEAF_ARRAY_BYTES; i++) {
 			if (byten == 0)
 				value = ldv(integer_size, buf);
 			la->la_array[i] = value >> shift;
@@ -321,10 +315,9 @@ zap_leaf_array_read(zap_leaf_t *l, uint16_t chunk,
 
 	while (len > 0) {
 		struct zap_leaf_array *la = &ZAP_LEAF_CHUNK(l, chunk).l_array;
-		int i;
 
 		ASSERT3U(chunk, <, ZAP_LEAF_NUMCHUNKS(l));
-		for (i = 0; i < ZAP_LEAF_ARRAY_BYTES && len > 0; i++) {
+		for (int i = 0; i < ZAP_LEAF_ARRAY_BYTES && len > 0; i++) {
 			value = (value << 8) | la->la_array[i];
 			byten++;
 			if (byten == array_int_len) {
@@ -347,16 +340,13 @@ zap_leaf_array_match(zap_leaf_t *l, zap_name_t *zn,
 	int bseen = 0;
 
 	if (zap_getflags(zn->zn_zap) & ZAP_FLAG_UINT64_KEY) {
-		uint64_t *thiskey;
-		boolean_t match;
-
+		uint64_t *thiskey =
+		    kmem_alloc(array_numints * sizeof (*thiskey), KM_SLEEP);
 		ASSERT(zn->zn_key_intlen == sizeof (*thiskey));
-		thiskey = kmem_alloc(array_numints * sizeof (*thiskey),
-		    KM_SLEEP);
 
 		zap_leaf_array_read(l, chunk, sizeof (*thiskey), array_numints,
 		    sizeof (*thiskey), array_numints, thiskey);
-		match = bcmp(thiskey, zn->zn_key_orig,
+		boolean_t match = bcmp(thiskey, zn->zn_key_orig,
 		    array_numints * sizeof (*thiskey)) == 0;
 		kmem_free(thiskey, array_numints * sizeof (*thiskey));
 		return (match);
@@ -365,11 +355,10 @@ zap_leaf_array_match(zap_leaf_t *l, zap_name_t *zn,
 	ASSERT(zn->zn_key_intlen == 1);
 	if (zn->zn_matchtype & MT_NORMALIZE) {
 		char *thisname = kmem_alloc(array_numints, KM_SLEEP);
-		boolean_t match;
 
 		zap_leaf_array_read(l, chunk, sizeof (char), array_numints,
 		    sizeof (char), array_numints, thisname);
-		match = zap_match(zn, thisname);
+		boolean_t match = zap_match(zn, thisname);
 		kmem_free(thisname, array_numints);
 		return (match);
 	}
@@ -400,12 +389,11 @@ zap_leaf_array_match(zap_leaf_t *l, zap_name_t *zn,
 int
 zap_leaf_lookup(zap_leaf_t *l, zap_name_t *zn, zap_entry_handle_t *zeh)
 {
-	uint16_t *chunkp;
 	struct zap_leaf_entry *le;
 
 	ASSERT3U(zap_leaf_phys(l)->l_hdr.lh_magic, ==, ZAP_LEAF_MAGIC);
 
-	for (chunkp = LEAF_HASH_ENTPTR(l, zn->zn_hash);
+	for (uint16_t *chunkp = LEAF_HASH_ENTPTR(l, zn->zn_hash);
 	    *chunkp != CHAIN_END; chunkp = &le->le_next) {
 		uint16_t chunk = *chunkp;
 		le = ZAP_LEAF_ENTRY(l, chunk);
@@ -446,17 +434,15 @@ int
 zap_leaf_lookup_closest(zap_leaf_t *l,
     uint64_t h, uint32_t cd, zap_entry_handle_t *zeh)
 {
-	uint16_t chunk;
 	uint64_t besth = -1ULL;
 	uint32_t bestcd = -1U;
 	uint16_t bestlh = ZAP_LEAF_HASH_NUMENTRIES(l)-1;
-	uint16_t lh;
 	struct zap_leaf_entry *le;
 
 	ASSERT3U(zap_leaf_phys(l)->l_hdr.lh_magic, ==, ZAP_LEAF_MAGIC);
 
-	for (lh = LEAF_HASH(l, h); lh <= bestlh; lh++) {
-		for (chunk = zap_leaf_phys(l)->l_hash[lh];
+	for (uint16_t lh = LEAF_HASH(l, h); lh <= bestlh; lh++) {
+		for (uint16_t chunk = zap_leaf_phys(l)->l_hash[lh];
 		    chunk != CHAIN_END; chunk = le->le_next) {
 			le = ZAP_LEAF_ENTRY(l, chunk);
 
@@ -529,11 +515,10 @@ int
 zap_entry_update(zap_entry_handle_t *zeh,
     uint8_t integer_size, uint64_t num_integers, const void *buf)
 {
-	int delta_chunks;
 	zap_leaf_t *l = zeh->zeh_leaf;
 	struct zap_leaf_entry *le = ZAP_LEAF_ENTRY(l, *zeh->zeh_chunkp);
 
-	delta_chunks = ZAP_LEAF_ARRAY_NCHUNKS(num_integers * integer_size) -
+	int delta_chunks = ZAP_LEAF_ARRAY_NCHUNKS(num_integers * integer_size) -
 	    ZAP_LEAF_ARRAY_NCHUNKS(le->le_value_numints * le->le_value_intlen);
 
 	if ((int)zap_leaf_phys(l)->l_hdr.lh_nfree < delta_chunks)
@@ -550,14 +535,12 @@ zap_entry_update(zap_entry_handle_t *zeh,
 void
 zap_entry_remove(zap_entry_handle_t *zeh)
 {
-	uint16_t entry_chunk;
-	struct zap_leaf_entry *le;
 	zap_leaf_t *l = zeh->zeh_leaf;
 
 	ASSERT3P(zeh->zeh_chunkp, !=, &zeh->zeh_fakechunk);
 
-	entry_chunk = *zeh->zeh_chunkp;
-	le = ZAP_LEAF_ENTRY(l, entry_chunk);
+	uint16_t entry_chunk = *zeh->zeh_chunkp;
+	struct zap_leaf_entry *le = ZAP_LEAF_ENTRY(l, entry_chunk);
 	ASSERT3U(le->le_type, ==, ZAP_CHUNK_ENTRY);
 
 	zap_leaf_array_free(l, &le->le_name_chunk);
@@ -575,15 +558,12 @@ zap_entry_create(zap_leaf_t *l, zap_name_t *zn, uint32_t cd,
     zap_entry_handle_t *zeh)
 {
 	uint16_t chunk;
-	uint16_t *chunkp;
 	struct zap_leaf_entry *le;
-	uint64_t valuelen;
-	int numchunks;
 	uint64_t h = zn->zn_hash;
 
-	valuelen = integer_size * num_integers;
+	uint64_t valuelen = integer_size * num_integers;
 
-	numchunks = 1 + ZAP_LEAF_ARRAY_NCHUNKS(zn->zn_key_orig_numints *
+	int numchunks = 1 + ZAP_LEAF_ARRAY_NCHUNKS(zn->zn_key_orig_numints *
 	    zn->zn_key_intlen) + ZAP_LEAF_ARRAY_NCHUNKS(valuelen);
 	if (numchunks > ZAP_LEAF_NUMCHUNKS(l))
 		return (E2BIG);
@@ -645,7 +625,7 @@ zap_entry_create(zap_leaf_t *l, zap_name_t *zn, uint32_t cd,
 
 	/* link it into the hash chain */
 	/* XXX if we did the search above, we could just use that */
-	chunkp = zap_leaf_rehash_entry(l, chunk);
+	uint16_t *chunkp = zap_leaf_rehash_entry(l, chunk);
 
 	zap_leaf_phys(l)->l_hdr.lh_nentries++;
 
@@ -673,14 +653,13 @@ boolean_t
 zap_entry_normalization_conflict(zap_entry_handle_t *zeh, zap_name_t *zn,
     const char *name, zap_t *zap)
 {
-	uint64_t chunk;
 	struct zap_leaf_entry *le;
 	boolean_t allocdzn = B_FALSE;
 
 	if (zap->zap_normflags == 0)
 		return (B_FALSE);
 
-	for (chunk = *LEAF_HASH_ENTPTR(zeh->zeh_leaf, zeh->zeh_hash);
+	for (uint16_t chunk = *LEAF_HASH_ENTPTR(zeh->zeh_leaf, zeh->zeh_hash);
 	    chunk != CHAIN_END; chunk = le->le_next) {
 		le = ZAP_LEAF_ENTRY(zeh->zeh_leaf, chunk);
 		if (le->le_hash != zeh->zeh_hash)
@@ -763,14 +742,11 @@ zap_leaf_transfer_array(zap_leaf_t *l, uint16_t chunk, zap_leaf_t *nl)
 static void
 zap_leaf_transfer_entry(zap_leaf_t *l, int entry, zap_leaf_t *nl)
 {
-	struct zap_leaf_entry *le, *nle;
-	uint16_t chunk;
-
-	le = ZAP_LEAF_ENTRY(l, entry);
+	struct zap_leaf_entry *le = ZAP_LEAF_ENTRY(l, entry);
 	ASSERT3U(le->le_type, ==, ZAP_CHUNK_ENTRY);
 
-	chunk = zap_leaf_chunk_alloc(nl);
-	nle = ZAP_LEAF_ENTRY(nl, chunk);
+	uint16_t chunk = zap_leaf_chunk_alloc(nl);
+	struct zap_leaf_entry *nle = ZAP_LEAF_ENTRY(nl, chunk);
 	*nle = *le; /* structure assignment */
 
 	(void) zap_leaf_rehash_entry(nl, chunk);
@@ -791,7 +767,6 @@ zap_leaf_transfer_entry(zap_leaf_t *l, int entry, zap_leaf_t *nl)
 void
 zap_leaf_split(zap_leaf_t *l, zap_leaf_t *nl, boolean_t sort)
 {
-	int i;
 	int bit = 64 - 1 - zap_leaf_phys(l)->l_hdr.lh_prefix_len;
 
 	/* set new prefix and prefix_len */
@@ -818,7 +793,7 @@ zap_leaf_split(zap_leaf_t *l, zap_leaf_t *nl, boolean_t sort)
 	 * but this accesses memory more sequentially, and when we're
 	 * called, the block is usually pretty full.
 	 */
-	for (i = 0; i < ZAP_LEAF_NUMCHUNKS(l); i++) {
+	for (int i = 0; i < ZAP_LEAF_NUMCHUNKS(l); i++) {
 		struct zap_leaf_entry *le = ZAP_LEAF_ENTRY(l, i);
 		if (le->le_type != ZAP_CHUNK_ENTRY)
 			continue;
@@ -833,9 +808,7 @@ zap_leaf_split(zap_leaf_t *l, zap_leaf_t *nl, boolean_t sort)
 void
 zap_leaf_stats(zap_t *zap, zap_leaf_t *l, zap_stats_t *zs)
 {
-	int i, n;
-
-	n = zap_f_phys(zap)->zap_ptrtbl.zt_shift -
+	int n = zap_f_phys(zap)->zap_ptrtbl.zt_shift -
 	    zap_leaf_phys(l)->l_hdr.lh_prefix_len;
 	n = MIN(n, ZAP_HISTOGRAM_SIZE-1);
 	zs->zs_leafs_with_2n_pointers[n]++;
@@ -851,7 +824,7 @@ zap_leaf_stats(zap_t *zap, zap_leaf_t *l, zap_stats_t *zs)
 	n = MIN(n, ZAP_HISTOGRAM_SIZE-1);
 	zs->zs_blocks_n_tenths_full[n]++;
 
-	for (i = 0; i < ZAP_LEAF_HASH_NUMENTRIES(l); i++) {
+	for (int i = 0; i < ZAP_LEAF_HASH_NUMENTRIES(l); i++) {
 		int nentries = 0;
 		int chunk = zap_leaf_phys(l)->l_hash[i];
 
diff --git a/usr/src/uts/common/fs/zfs/zap_micro.c b/usr/src/uts/common/fs/zfs/zap_micro.c
index 15dda6856b..b07079ed44 100644
--- a/usr/src/uts/common/fs/zfs/zap_micro.c
+++ b/usr/src/uts/common/fs/zfs/zap_micro.c
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  * Copyright (c) 2014 Integros [integros.com]
  * Copyright 2017 Nexenta Systems, Inc.
@@ -89,22 +89,20 @@ zap_hash(zap_name_t *zn)
 		ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
 
 		if (zap_getflags(zap) & ZAP_FLAG_UINT64_KEY) {
-			int i;
 			const uint64_t *wp = zn->zn_key_norm;
 
 			ASSERT(zn->zn_key_intlen == 8);
-			for (i = 0; i < zn->zn_key_norm_numints; wp++, i++) {
-				int j;
+			for (int i = 0; i < zn->zn_key_norm_numints;
+			    wp++, i++) {
 				uint64_t word = *wp;
 
-				for (j = 0; j < zn->zn_key_intlen; j++) {
+				for (int j = 0; j < zn->zn_key_intlen; j++) {
 					h = (h >> 8) ^
 					    zfs_crc64_table[(h ^ word) & 0xFF];
 					word >>= NBBY;
 				}
 			}
 		} else {
-			int i, len;
 			const uint8_t *cp = zn->zn_key_norm;
 
 			/*
@@ -114,10 +112,10 @@ zap_hash(zap_name_t *zn)
 			 * zn_key_*_numints includes the terminating
 			 * null for non-binary keys.)
 			 */
-			len = zn->zn_key_norm_numints - 1;
+			int len = zn->zn_key_norm_numints - 1;
 
 			ASSERT(zn->zn_key_intlen == 1);
-			for (i = 0; i < len; cp++, i++) {
+			for (int i = 0; i < len; cp++, i++) {
 				h = (h >> 8) ^
 				    zfs_crc64_table[(h ^ *cp) & 0xFF];
 			}
@@ -137,15 +135,12 @@ zap_hash(zap_name_t *zn)
 static int
 zap_normalize(zap_t *zap, const char *name, char *namenorm, int normflags)
 {
-	size_t inlen, outlen;
-	int err;
-
 	ASSERT(!(zap_getflags(zap) & ZAP_FLAG_UINT64_KEY));
 
-	inlen = strlen(name) + 1;
-	outlen = ZAP_MAXNAMELEN;
+	size_t inlen = strlen(name) + 1;
+	size_t outlen = ZAP_MAXNAMELEN;
 
-	err = 0;
+	int err = 0;
 	(void) u8_textprep_str((char *)name, &inlen, namenorm, &outlen,
 	    normflags | U8_TEXTPREP_IGNORE_NULL | U8_TEXTPREP_IGNORE_INVALID,
 	    U8_UNICODE_LATEST, &err);
@@ -255,12 +250,11 @@ zap_name_alloc_uint64(zap_t *zap, const uint64_t *key, int numints)
 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++) {
+	int max = (size / MZAP_ENT_LEN) - 1;
+	for (int 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 =
@@ -271,9 +265,7 @@ mzap_byteswap(mzap_phys_t *buf, size_t size)
 void
 zap_byteswap(void *buf, size_t size)
 {
-	uint64_t block_type;
-
-	block_type = *(uint64_t *)buf;
+	uint64_t block_type = *(uint64_t *)buf;
 
 	if (block_type == ZBT_MICRO || block_type == BSWAP_64(ZBT_MICRO)) {
 		/* ASSERT(magic == ZAP_LEAF_MAGIC); */
@@ -303,12 +295,10 @@ mze_compare(const void *arg1, const void *arg2)
 static void
 mze_insert(zap_t *zap, int chunkid, uint64_t hash)
 {
-	mzap_ent_t *mze;
-
 	ASSERT(zap->zap_ismicro);
 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
 
-	mze = kmem_alloc(sizeof (mzap_ent_t), KM_SLEEP);
+	mzap_ent_t *mze = kmem_alloc(sizeof (mzap_ent_t), KM_SLEEP);
 	mze->mze_chunkid = chunkid;
 	mze->mze_hash = hash;
 	mze->mze_cd = MZE_PHYS(zap, mze)->mze_cd;
@@ -346,10 +336,8 @@ 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));
@@ -357,8 +345,8 @@ mze_find_unused_cd(zap_t *zap, uint64_t hash)
 	mze_tofind.mze_hash = hash;
 	mze_tofind.mze_cd = 0;
 
-	cd = 0;
-	for (mze = avl_find(avl, &mze_tofind, &idx);
+	uint32_t cd = 0;
+	for (mzap_ent_t *mze = avl_find(avl, &mze_tofind, &idx);
 	    mze && mze->mze_hash == hash; mze = AVL_NEXT(avl, mze)) {
 		if (mze->mze_cd != cd)
 			break;
@@ -393,15 +381,13 @@ static zap_t *
 mzap_open(objset_t *os, uint64_t obj, dmu_buf_t *db)
 {
 	zap_t *winner;
-	zap_t *zap;
-	int i;
 	uint64_t *zap_hdr = (uint64_t *)db->db_data;
 	uint64_t zap_block_type = zap_hdr[0];
 	uint64_t zap_magic = zap_hdr[1];
 
 	ASSERT3U(MZAP_ENT_LEN, ==, sizeof (mzap_ent_phys_t));
 
-	zap = kmem_zalloc(sizeof (zap_t), KM_SLEEP);
+	zap_t *zap = kmem_zalloc(sizeof (zap_t), KM_SLEEP);
 	rw_init(&zap->zap_rwlock, 0, 0, 0);
 	rw_enter(&zap->zap_rwlock, RW_WRITER);
 	zap->zap_objset = os;
@@ -437,7 +423,7 @@ mzap_open(objset_t *os, uint64_t obj, dmu_buf_t *db)
 		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++) {
+		for (int i = 0; i < zap->zap_m.zap_num_chunks; i++) {
 			mzap_ent_phys_t *mze =
 			    &zap_m_phys(zap)->mz_chunk[i];
 			if (mze->mze_name[0]) {
@@ -484,28 +470,21 @@ handle_winner:
 	return (winner);
 }
 
+/*
+ * This routine "consumes" the caller's hold on the dbuf, which must
+ * have the specified tag.
+ */
 static int
 zap_lockdir_impl(dmu_buf_t *db, void *tag, dmu_tx_t *tx,
     krw_t lti, boolean_t fatreader, boolean_t adding, zap_t **zapp)
 {
-	zap_t *zap;
-	krw_t lt;
-
 	ASSERT0(db->db_offset);
 	objset_t *os = dmu_buf_get_objset(db);
 	uint64_t obj = db->db_object;
 
 	*zapp = NULL;
 
-#ifdef ZFS_DEBUG
-	{
-		dmu_object_info_t doi;
-		dmu_object_info_from_db(db, &doi);
-		ASSERT3U(DMU_OT_BYTESWAP(doi.doi_type), ==, DMU_BSWAP_ZAP);
-	}
-#endif
-
-	zap = dmu_buf_get_user(db);
+	zap_t *zap = dmu_buf_get_user(db);
 	if (zap == NULL) {
 		zap = mzap_open(os, obj, db);
 		if (zap == NULL) {
@@ -524,7 +503,7 @@ zap_lockdir_impl(dmu_buf_t *db, void *tag, dmu_tx_t *tx,
 	 * 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;
+	krw_t 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 */
@@ -570,12 +549,19 @@ zap_lockdir_by_dnode(dnode_t *dn, dmu_tx_t *tx,
     krw_t lti, boolean_t fatreader, boolean_t adding, void *tag, zap_t **zapp)
 {
 	dmu_buf_t *db;
-	int err;
 
-	err = dmu_buf_hold_by_dnode(dn, 0, tag, &db, DMU_READ_NO_PREFETCH);
+	int err = dmu_buf_hold_by_dnode(dn, 0, tag, &db, DMU_READ_NO_PREFETCH);
 	if (err != 0) {
 		return (err);
 	}
+#ifdef ZFS_DEBUG
+	{
+		dmu_object_info_t doi;
+		dmu_object_info_from_db(db, &doi);
+		ASSERT3U(DMU_OT_BYTESWAP(doi.doi_type), ==, DMU_BSWAP_ZAP);
+	}
+#endif
+
 	err = zap_lockdir_impl(db, tag, tx, lti, fatreader, adding, zapp);
 	if (err != 0) {
 		dmu_buf_rele(db, tag);
@@ -588,11 +574,17 @@ zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
     krw_t lti, boolean_t fatreader, boolean_t adding, void *tag, zap_t **zapp)
 {
 	dmu_buf_t *db;
-	int err;
 
-	err = dmu_buf_hold(os, obj, 0, tag, &db, DMU_READ_NO_PREFETCH);
+	int err = dmu_buf_hold(os, obj, 0, tag, &db, DMU_READ_NO_PREFETCH);
 	if (err != 0)
 		return (err);
+#ifdef ZFS_DEBUG
+	{
+		dmu_object_info_t doi;
+		dmu_object_info_from_db(db, &doi);
+		ASSERT3U(DMU_OT_BYTESWAP(doi.doi_type), ==, DMU_BSWAP_ZAP);
+	}
+#endif
 	err = zap_lockdir_impl(db, tag, tx, lti, fatreader, adding, zapp);
 	if (err != 0)
 		dmu_buf_rele(db, tag);
@@ -609,22 +601,20 @@ zap_unlockdir(zap_t *zap, void *tag)
 static int
 mzap_upgrade(zap_t **zapp, void *tag, dmu_tx_t *tx, zap_flags_t flags)
 {
-	mzap_phys_t *mzp;
-	int i, sz, nchunks;
 	int err = 0;
 	zap_t *zap = *zapp;
 
 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
 
-	sz = zap->zap_dbuf->db_size;
-	mzp = zio_buf_alloc(sz);
+	int sz = zap->zap_dbuf->db_size;
+	mzap_phys_t *mzp = zio_buf_alloc(sz);
 	bcopy(zap->zap_dbuf->db_data, mzp, sz);
-	nchunks = zap->zap_m.zap_num_chunks;
+	int nchunks = zap->zap_m.zap_num_chunks;
 
 	if (!flags) {
 		err = dmu_object_set_blocksize(zap->zap_objset, zap->zap_object,
 		    1ULL << fzap_default_block_shift, 0, tx);
-		if (err) {
+		if (err != 0) {
 			zio_buf_free(mzp, sz);
 			return (err);
 		}
@@ -637,19 +627,18 @@ mzap_upgrade(zap_t **zapp, void *tag, dmu_tx_t *tx, zap_flags_t flags)
 
 	fzap_upgrade(zap, tx, flags);
 
-	for (i = 0; i < nchunks; i++) {
+	for (int i = 0; i < nchunks; i++) {
 		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, 0);
+		zap_name_t *zn = zap_name_alloc(zap, mze->mze_name, 0);
 		err = fzap_add_cd(zn, 8, 1, &mze->mze_value, mze->mze_cd,
 		    tag, tx);
 		zap = zn->zn_zap;	/* fzap_add_cd() may change zap */
 		zap_name_free(zn);
-		if (err)
+		if (err != 0)
 			break;
 	}
 	zio_buf_free(mzp, sz);
@@ -679,32 +668,24 @@ mzap_create_impl(objset_t *os, uint64_t obj, int normflags, zap_flags_t flags,
     dmu_tx_t *tx)
 {
 	dmu_buf_t *db;
-	mzap_phys_t *zp;
-
-	VERIFY(0 == dmu_buf_hold(os, obj, 0, FTAG, &db, DMU_READ_NO_PREFETCH));
 
-#ifdef ZFS_DEBUG
-	{
-		dmu_object_info_t doi;
-		dmu_object_info_from_db(db, &doi);
-		ASSERT3U(DMU_OT_BYTESWAP(doi.doi_type), ==, DMU_BSWAP_ZAP);
-	}
-#endif
+	VERIFY0(dmu_buf_hold(os, obj, 0, FTAG, &db, DMU_READ_NO_PREFETCH));
 
 	dmu_buf_will_dirty(db, tx);
-	zp = db->db_data;
+	mzap_phys_t *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);
 
 	if (flags != 0) {
 		zap_t *zap;
 		/* Only fat zap supports flags; upgrade immediately. */
-		VERIFY(0 == zap_lockdir(os, obj, tx, RW_WRITER,
-		    B_FALSE, B_FALSE, FTAG, &zap));
-		VERIFY3U(0, ==, mzap_upgrade(&zap, FTAG, tx, flags));
+		VERIFY0(zap_lockdir_impl(db, FTAG, tx, RW_WRITER,
+		    B_FALSE, B_FALSE, &zap));
+		VERIFY0(mzap_upgrade(&zap, FTAG, tx, flags));
 		zap_unlockdir(zap, FTAG);
+	} else {
+		dmu_buf_rele(db, FTAG);
 	}
 }
 
@@ -721,9 +702,8 @@ 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);
+	ASSERT3U(DMU_OT_BYTESWAP(ot), ==, DMU_BSWAP_ZAP);
+	int err = dmu_object_claim(os, obj, ot, 0, bonustype, bonuslen, tx);
 	if (err != 0)
 		return (err);
 	mzap_create_impl(os, obj, normflags, 0, tx);
@@ -741,6 +721,7 @@ 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)
 {
+	ASSERT3U(DMU_OT_BYTESWAP(ot), ==, DMU_BSWAP_ZAP);
 	uint64_t obj = dmu_object_alloc(os, ot, 0, bonustype, bonuslen, tx);
 
 	mzap_create_impl(os, obj, normflags, 0, tx);
@@ -752,6 +733,7 @@ zap_create_flags(objset_t *os, int normflags, zap_flags_t flags,
     dmu_object_type_t ot, int leaf_blockshift, int indirect_blockshift,
     dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
 {
+	ASSERT3U(DMU_OT_BYTESWAP(ot), ==, DMU_BSWAP_ZAP);
 	uint64_t obj = dmu_object_alloc(os, ot, 0, bonustype, bonuslen, tx);
 
 	ASSERT(leaf_blockshift >= SPA_MINBLOCKSHIFT &&
@@ -797,10 +779,10 @@ 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, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
 		return (err);
 	if (!zap->zap_ismicro) {
 		err = fzap_count(zap, count);
@@ -818,7 +800,6 @@ zap_count(objset_t *os, uint64_t zapobj, uint64_t *count)
 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;
 
@@ -826,7 +807,7 @@ mzap_normalization_conflict(zap_t *zap, zap_name_t *zn, mzap_ent_t *mze)
 		return (B_FALSE);
 
 again:
-	for (other = avl_walk(&zap->zap_m.zap_avl, mze, direction);
+	for (mzap_ent_t *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)) {
 
@@ -871,10 +852,8 @@ zap_lookup_impl(zap_t *zap, const char *name,
     boolean_t *ncp)
 {
 	int err = 0;
-	mzap_ent_t *mze;
-	zap_name_t *zn;
 
-	zn = zap_name_alloc(zap, name, mt);
+	zap_name_t *zn = zap_name_alloc(zap, name, mt);
 	if (zn == NULL)
 		return (SET_ERROR(ENOTSUP));
 
@@ -882,7 +861,7 @@ zap_lookup_impl(zap_t *zap, const char *name,
 		err = fzap_lookup(zn, integer_size, num_integers, buf,
 		    realname, rn_len, ncp);
 	} else {
-		mze = mze_find(zn);
+		mzap_ent_t *mze = mze_find(zn);
 		if (mze == NULL) {
 			err = SET_ERROR(ENOENT);
 		} else {
@@ -913,9 +892,9 @@ zap_lookup_norm(objset_t *os, uint64_t zapobj, const char *name,
     boolean_t *ncp)
 {
 	zap_t *zap;
-	int err;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	int err =
+	    zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err != 0)
 		return (err);
 	err = zap_lookup_impl(zap, name, integer_size,
@@ -939,9 +918,8 @@ zap_lookup_norm_by_dnode(dnode_t *dn, const char *name,
     boolean_t *ncp)
 {
 	zap_t *zap;
-	int err;
 
-	err = zap_lockdir_by_dnode(dn, NULL, RW_READER, TRUE, FALSE,
+	int err = zap_lockdir_by_dnode(dn, NULL, RW_READER, TRUE, FALSE,
 	    FTAG, &zap);
 	if (err != 0)
 		return (err);
@@ -956,13 +934,12 @@ zap_prefetch_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
     int key_numints)
 {
 	zap_t *zap;
-	int err;
-	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc_uint64(zap, key, key_numints);
+	zap_name_t *zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -979,13 +956,12 @@ zap_lookup_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
     int key_numints, uint64_t integer_size, uint64_t num_integers, void *buf)
 {
 	zap_t *zap;
-	int err;
-	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc_uint64(zap, key, key_numints);
+	zap_name_t *zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -1013,14 +989,12 @@ 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, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc(zap, name, 0);
+	zap_name_t *zn = zap_name_alloc(zap, name, 0);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -1028,7 +1002,7 @@ zap_length(objset_t *os, uint64_t zapobj, const char *name,
 	if (!zap->zap_ismicro) {
 		err = fzap_length(zn, integer_size, num_integers);
 	} else {
-		mze = mze_find(zn);
+		mzap_ent_t *mze = mze_find(zn);
 		if (mze == NULL) {
 			err = SET_ERROR(ENOENT);
 		} else {
@@ -1048,13 +1022,12 @@ zap_length_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
     int key_numints, uint64_t *integer_size, uint64_t *num_integers)
 {
 	zap_t *zap;
-	int err;
-	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc_uint64(zap, key, key_numints);
+	zap_name_t *zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -1068,26 +1041,24 @@ zap_length_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 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;
 
 	ASSERT(RW_WRITE_HELD(&zap->zap_rwlock));
 
 #ifdef ZFS_DEBUG
-	for (i = 0; i < zap->zap_m.zap_num_chunks; i++) {
+	for (int i = 0; i < zap->zap_m.zap_num_chunks; i++) {
 		mzap_ent_phys_t *mze = &zap_m_phys(zap)->mz_chunk[i];
 		ASSERT(strcmp(zn->zn_key_orig, mze->mze_name) != 0);
 	}
 #endif
 
-	cd = mze_find_unused_cd(zap, zn->zn_hash);
+	uint32_t cd = mze_find_unused_cd(zap, zn->zn_hash);
 	/* given the limited size of the microzap, this can't happen */
 	ASSERT(cd < zap_maxcd(zap));
 
 again:
-	for (i = start; i < zap->zap_m.zap_num_chunks; i++) {
+	for (int i = start; i < zap->zap_m.zap_num_chunks; i++) {
 		mzap_ent_phys_t *mze = &zap_m_phys(zap)->mz_chunk[i];
 		if (mze->mze_name[0] == 0) {
 			mze->mze_value = value;
@@ -1114,12 +1085,10 @@ zap_add_impl(zap_t *zap, const char *key,
     int integer_size, uint64_t num_integers,
     const void *val, dmu_tx_t *tx, void *tag)
 {
-	int err = 0;
-	mzap_ent_t *mze;
 	const uint64_t *intval = val;
-	zap_name_t *zn;
+	int err = 0;
 
-	zn = zap_name_alloc(zap, key, 0);
+	zap_name_t *zn = zap_name_alloc(zap, key, 0);
 	if (zn == NULL) {
 		zap_unlockdir(zap, tag);
 		return (SET_ERROR(ENOTSUP));
@@ -1136,8 +1105,7 @@ zap_add_impl(zap_t *zap, const char *key,
 		}
 		zap = zn->zn_zap;	/* fzap_add() may change zap */
 	} else {
-		mze = mze_find(zn);
-		if (mze != NULL) {
+		if (mze_find(zn) != NULL) {
 			err = SET_ERROR(EEXIST);
 		} else {
 			mzap_addent(zn, *intval);
@@ -1188,13 +1156,12 @@ zap_add_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
     const void *val, dmu_tx_t *tx)
 {
 	zap_t *zap;
-	int err;
-	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc_uint64(zap, key, key_numints);
+	zap_name_t *zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -1212,11 +1179,8 @@ 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;
 	uint64_t oldval;
 	const uint64_t *intval = val;
-	zap_name_t *zn;
-	int err;
 
 #ifdef ZFS_DEBUG
 	/*
@@ -1227,10 +1191,11 @@ zap_update(objset_t *os, uint64_t zapobj, const char *name,
 		(void) zap_lookup(os, zapobj, name, 8, 1, &oldval);
 #endif
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc(zap, name, 0);
+	zap_name_t *zn = zap_name_alloc(zap, name, 0);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -1250,7 +1215,7 @@ zap_update(objset_t *os, uint64_t zapobj, const char *name,
 		}
 		zap = zn->zn_zap;	/* fzap_update() may change zap */
 	} else {
-		mze = mze_find(zn);
+		mzap_ent_t *mze = mze_find(zn);
 		if (mze != NULL) {
 			ASSERT3U(MZE_PHYS(zap, mze)->mze_value, ==, oldval);
 			MZE_PHYS(zap, mze)->mze_value = *intval;
@@ -1271,13 +1236,12 @@ zap_update_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
     int integer_size, uint64_t num_integers, const void *val, dmu_tx_t *tx)
 {
 	zap_t *zap;
-	zap_name_t *zn;
-	int err;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc_uint64(zap, key, key_numints);
+	zap_name_t *zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -1300,17 +1264,15 @@ static int
 zap_remove_impl(zap_t *zap, const char *name,
     matchtype_t mt, dmu_tx_t *tx)
 {
-	mzap_ent_t *mze;
-	zap_name_t *zn;
 	int err = 0;
 
-	zn = zap_name_alloc(zap, name, mt);
+	zap_name_t *zn = zap_name_alloc(zap, name, mt);
 	if (zn == NULL)
 		return (SET_ERROR(ENOTSUP));
 	if (!zap->zap_ismicro) {
 		err = fzap_remove(zn, tx);
 	} else {
-		mze = mze_find(zn);
+		mzap_ent_t *mze = mze_find(zn);
 		if (mze == NULL) {
 			err = SET_ERROR(ENOENT);
 		} else {
@@ -1358,13 +1320,12 @@ zap_remove_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
     int key_numints, dmu_tx_t *tx)
 {
 	zap_t *zap;
-	int err;
-	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, FALSE, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
 		return (err);
-	zn = zap_name_alloc_uint64(zap, key, key_numints);
+	zap_name_t *zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
 		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
@@ -1440,9 +1401,6 @@ 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 (SET_ERROR(ENOENT));
@@ -1451,7 +1409,7 @@ zap_cursor_retrieve(zap_cursor_t *zc, zap_attribute_t *za)
 		int hb;
 		err = zap_lockdir(zc->zc_objset, zc->zc_zapobj, NULL,
 		    RW_READER, TRUE, FALSE, NULL, &zc->zc_zap);
-		if (err)
+		if (err != 0)
 			return (err);
 
 		/*
@@ -1471,10 +1429,14 @@ zap_cursor_retrieve(zap_cursor_t *zc, zap_attribute_t *za)
 	if (!zc->zc_zap->zap_ismicro) {
 		err = fzap_cursor_retrieve(zc->zc_zap, zc, za);
 	} else {
+		avl_index_t idx;
+		mzap_ent_t mze_tofind;
+
 		mze_tofind.mze_hash = zc->zc_hash;
 		mze_tofind.mze_cd = zc->zc_cd;
 
-		mze = avl_find(&zc->zc_zap->zap_m.zap_avl, &mze_tofind, &idx);
+		mzap_ent_t *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);
@@ -1511,11 +1473,11 @@ zap_cursor_advance(zap_cursor_t *zc)
 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, FTAG, &zap);
-	if (err)
+	int err =
+	    zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
 		return (err);
 
 	bzero(zs, sizeof (zap_stats_t));