OpenZFS 6314 - buffer overflow in dsl_dataset_name

Reviewed by: George Wilson <[email protected]>
Reviewed by: Prakash Surya <[email protected]>
Reviewed by: Igor Kozhukhov <[email protected]>
Approved by: Dan McDonald <[email protected]>
Ported-by: Brian Behlendorf <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/6314
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d6160ee

41 files changed, 298 insertions, 335 deletions

diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
index ee5e21f10..967d74216 100644
--- a/cmd/zdb/zdb.c
+++ b/cmd/zdb/zdb.c
@@ -60,7 +60,6 @@
 #include <sys/ddt.h>
 #include <sys/zfeature.h>
 #include <zfs_comutil.h>
-#undef ZFS_MAXNAMELEN
 #include <libzfs.h>
 
 #define	ZDB_COMPRESS_NAME(idx) ((idx) < ZIO_COMPRESS_FUNCTIONS ?	\
@@ -2005,7 +2004,7 @@ dump_dir(objset_t *os)
 	uint64_t refdbytes, usedobjs, scratch;
 	char numbuf[32];
 	char blkbuf[BP_SPRINTF_LEN + 20];
-	char osname[MAXNAMELEN];
+	char osname[ZFS_MAX_DATASET_NAME_LEN];
 	char *type = "UNKNOWN";
 	int verbosity = dump_opt['d'];
 	int print_header = 1;
@@ -3553,7 +3552,7 @@ find_zpool(char **target, nvlist_t **configp, int dirc, char **dirv)
 	nvlist_t *match = NULL;
 	char *name = NULL;
 	char *sepp = NULL;
-	char sep = 0;
+	char sep = '\0';
 	int count = 0;
 	importargs_t args = { 0 };
 
diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index 3d20973a2..e8a4421cc 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -1483,7 +1483,7 @@ get_callback(zfs_handle_t *zhp, void *data)
 	char buf[ZFS_MAXPROPLEN];
 	char rbuf[ZFS_MAXPROPLEN];
 	zprop_source_t sourcetype;
-	char source[ZFS_MAXNAMELEN];
+	char source[ZFS_MAX_DATASET_NAME_LEN];
 	zprop_get_cbdata_t *cbp = data;
 	nvlist_t *user_props = zfs_get_user_props(zhp);
 	zprop_list_t *pl = cbp->cb_proplist;
@@ -1963,7 +1963,7 @@ typedef struct upgrade_cbdata {
 	uint64_t cb_version;
 	boolean_t cb_newer;
 	boolean_t cb_foundone;
-	char cb_lastfs[ZFS_MAXNAMELEN];
+	char cb_lastfs[ZFS_MAX_DATASET_NAME_LEN];
 } upgrade_cbdata_t;
 
 static int
@@ -2412,7 +2412,7 @@ userspace_cb(void *arg, const char *domain, uid_t rid, uint64_t space)
 	if (domain != NULL && domain[0] != '\0') {
 #ifdef HAVE_IDMAP
 		/* SMB */
-		char sid[ZFS_MAXNAMELEN + 32];
+		char sid[MAXNAMELEN + 32];
 		uid_t id;
 		uint64_t classes;
 		int err;
@@ -2546,7 +2546,7 @@ print_us_node(boolean_t scripted, boolean_t parsable, int *fields, int types,
     size_t *width, us_node_t *node)
 {
 	nvlist_t *nvl = node->usn_nvl;
-	char valstr[ZFS_MAXNAMELEN];
+	char valstr[MAXNAMELEN];
 	boolean_t first = B_TRUE;
 	int cfield = 0;
 	int field;
@@ -3417,7 +3417,7 @@ zfs_do_rollback(int argc, char **argv)
 	boolean_t force = B_FALSE;
 	rollback_cbdata_t cb = { 0 };
 	zfs_handle_t *zhp, *snap;
-	char parentname[ZFS_MAXNAMELEN];
+	char parentname[ZFS_MAX_DATASET_NAME_LEN];
 	char *delim;
 
 	/* check options */
@@ -3818,7 +3818,7 @@ zfs_do_send(int argc, char **argv)
 	 */
 	if (strchr(argv[0], '@') == NULL ||
 	    (fromname && strchr(fromname, '#') != NULL)) {
-		char frombuf[ZFS_MAXNAMELEN];
+		char frombuf[ZFS_MAX_DATASET_NAME_LEN];
 		enum lzc_send_flags lzc_flags = 0;
 
 		if (flags.replicate || flags.doall || flags.props ||
@@ -3870,7 +3870,7 @@ zfs_do_send(int argc, char **argv)
 	 * case if they specify the origin.
 	 */
 	if (fromname && (cp = strchr(fromname, '@')) != NULL) {
-		char origin[ZFS_MAXNAMELEN];
+		char origin[ZFS_MAX_DATASET_NAME_LEN];
 		zprop_source_t src;
 
 		(void) zfs_prop_get(zhp, ZFS_PROP_ORIGIN,
@@ -4004,7 +4004,7 @@ zfs_do_receive(int argc, char **argv)
 			usage(B_FALSE);
 		}
 
-		char namebuf[ZFS_MAXNAMELEN];
+		char namebuf[ZFS_MAX_DATASET_NAME_LEN];
 		(void) snprintf(namebuf, sizeof (namebuf),
 		    "%s/%%recv", argv[0]);
 
@@ -4860,7 +4860,7 @@ store_allow_perm(zfs_deleg_who_type_t type, boolean_t local, boolean_t descend,
 {
 	int i;
 	char ld[2] = { '\0', '\0' };
-	char who_buf[ZFS_MAXNAMELEN+32];
+	char who_buf[MAXNAMELEN + 32];
 	char base_type = ZFS_DELEG_WHO_UNKNOWN;
 	char set_type = ZFS_DELEG_WHO_UNKNOWN;
 	nvlist_t *base_nvl = NULL;
@@ -5224,7 +5224,7 @@ static void
 print_fs_perms(fs_perm_set_t *fspset)
 {
 	fs_perm_node_t *node = NULL;
-	char buf[ZFS_MAXNAMELEN+32];
+	char buf[MAXNAMELEN + 32];
 	const char *dsname = buf;
 
 	for (node = uu_list_first(fspset->fsps_list); node != NULL;
@@ -5233,7 +5233,7 @@ print_fs_perms(fs_perm_set_t *fspset)
 		uu_avl_t *uge_avl = node->fspn_fsperm.fsp_uge_avl;
 		int left = 0;
 
-		(void) snprintf(buf, ZFS_MAXNAMELEN+32,
+		(void) snprintf(buf, sizeof (buf),
 		    gettext("---- Permissions on %s "),
 		    node->fspn_fsperm.fsp_name);
 		(void) printf("%s", dsname);
@@ -5430,7 +5430,7 @@ zfs_do_hold_rele_impl(int argc, char **argv, boolean_t holding)
 
 	for (i = 0; i < argc; ++i) {
 		zfs_handle_t *zhp;
-		char parent[ZFS_MAXNAMELEN];
+		char parent[ZFS_MAX_DATASET_NAME_LEN];
 		const char *delim;
 		char *path = argv[i];
 
@@ -5558,7 +5558,7 @@ holds_callback(zfs_handle_t *zhp, void *data)
 	nvlist_t *nvl = NULL;
 	nvpair_t *nvp = NULL;
 	const char *zname = zfs_get_name(zhp);
-	size_t znamelen = strnlen(zname, ZFS_MAXNAMELEN);
+	size_t znamelen = strlen(zname);
 
 	if (cbp->cb_recursive) {
 		const char *snapname;
@@ -5579,7 +5579,7 @@ holds_callback(zfs_handle_t *zhp, void *data)
 
 	while ((nvp = nvlist_next_nvpair(nvl, nvp)) != NULL) {
 		const char *tag = nvpair_name(nvp);
-		size_t taglen = strnlen(tag, MAXNAMELEN);
+		size_t taglen = strlen(tag);
 		if (taglen > cbp->cb_max_taglen)
 			cbp->cb_max_taglen  = taglen;
 	}
@@ -6695,7 +6695,7 @@ zfs_do_diff(int argc, char **argv)
 static int
 zfs_do_bookmark(int argc, char **argv)
 {
-	char snapname[ZFS_MAXNAMELEN];
+	char snapname[ZFS_MAX_DATASET_NAME_LEN];
 	zfs_handle_t *zhp;
 	nvlist_t *nvl;
 	int ret = 0;
diff --git a/cmd/zhack/zhack.c b/cmd/zhack/zhack.c
index eedd17c30..cc4f174c6 100644
--- a/cmd/zhack/zhack.c
+++ b/cmd/zhack/zhack.c
@@ -48,7 +48,6 @@
 #include <sys/zio_compress.h>
 #include <sys/zfeature.h>
 #include <sys/dmu_tx.h>
-#undef ZFS_MAXNAMELEN
 #include <libzfs.h>
 
 extern boolean_t zfeature_checks_disable;
diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index ad15dea1d..2cc410f10 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -145,8 +145,8 @@ typedef struct ztest_shared_hdr {
 static ztest_shared_hdr_t *ztest_shared_hdr;
 
 typedef struct ztest_shared_opts {
-	char zo_pool[MAXNAMELEN];
-	char zo_dir[MAXNAMELEN];
+	char zo_pool[ZFS_MAX_DATASET_NAME_LEN];
+	char zo_dir[ZFS_MAX_DATASET_NAME_LEN];
 	char zo_alt_ztest[MAXNAMELEN];
 	char zo_alt_libpath[MAXNAMELEN];
 	uint64_t zo_vdevs;
@@ -262,7 +262,7 @@ typedef struct ztest_od {
 	uint64_t	od_crdnodesize;
 	uint64_t	od_gen;
 	uint64_t	od_crgen;
-	char		od_name[MAXNAMELEN];
+	char		od_name[ZFS_MAX_DATASET_NAME_LEN];
 } ztest_od_t;
 
 /*
@@ -274,7 +274,7 @@ typedef struct ztest_ds {
 	rwlock_t	zd_zilog_lock;
 	zilog_t		*zd_zilog;
 	ztest_od_t	*zd_od;		/* debugging aid */
-	char		zd_name[MAXNAMELEN];
+	char		zd_name[ZFS_MAX_DATASET_NAME_LEN];
 	kmutex_t	zd_dirobj_lock;
 	rll_t		zd_object_lock[ZTEST_OBJECT_LOCKS];
 	zll_t		zd_range_lock[ZTEST_RANGE_LOCKS];
@@ -3504,7 +3504,7 @@ ztest_objset_destroy_cb(const char *name, void *arg)
 static boolean_t
 ztest_snapshot_create(char *osname, uint64_t id)
 {
-	char snapname[MAXNAMELEN];
+	char snapname[ZFS_MAX_DATASET_NAME_LEN];
 	int error;
 
 	(void) snprintf(snapname, sizeof (snapname), "%llu", (u_longlong_t)id);
@@ -3524,10 +3524,10 @@ ztest_snapshot_create(char *osname, uint64_t id)
 static boolean_t
 ztest_snapshot_destroy(char *osname, uint64_t id)
 {
-	char snapname[MAXNAMELEN];
+	char snapname[ZFS_MAX_DATASET_NAME_LEN];
 	int error;
 
-	(void) snprintf(snapname, MAXNAMELEN, "%s@%llu", osname,
+	(void) snprintf(snapname, sizeof (snapname), "%s@%llu", osname,
 	    (u_longlong_t)id);
 
 	error = dsl_destroy_snapshot(snapname, B_FALSE);
@@ -3544,16 +3544,15 @@ ztest_dmu_objset_create_destroy(ztest_ds_t *zd, uint64_t id)
 	int iters;
 	int error;
 	objset_t *os, *os2;
-	char *name;
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	zilog_t *zilog;
 	int i;
 
 	zdtmp = umem_alloc(sizeof (ztest_ds_t), UMEM_NOFAIL);
-	name = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
 
 	(void) rw_rdlock(&ztest_name_lock);
 
-	(void) snprintf(name, MAXNAMELEN, "%s/temp_%llu",
+	(void) snprintf(name, sizeof (name), "%s/temp_%llu",
 	    ztest_opts.zo_pool, (u_longlong_t)id);
 
 	/*
@@ -3639,7 +3638,6 @@ ztest_dmu_objset_create_destroy(ztest_ds_t *zd, uint64_t id)
 out:
 	(void) rw_unlock(&ztest_name_lock);
 
-	umem_free(name, MAXNAMELEN);
 	umem_free(zdtmp, sizeof (ztest_ds_t));
 }
 
@@ -3668,22 +3666,22 @@ ztest_dsl_dataset_cleanup(char *osname, uint64_t id)
 	char *snap3name;
 	int error;
 
-	snap1name  = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	clone1name = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	snap2name  = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	clone2name = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	snap3name  = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-
-	(void) snprintf(snap1name, MAXNAMELEN, "%s@s1_%llu",
-	    osname, (u_longlong_t)id);
-	(void) snprintf(clone1name, MAXNAMELEN, "%s/c1_%llu",
-	    osname, (u_longlong_t)id);
-	(void) snprintf(snap2name, MAXNAMELEN, "%s@s2_%llu",
-	    clone1name, (u_longlong_t)id);
-	(void) snprintf(clone2name, MAXNAMELEN, "%s/c2_%llu",
-	    osname, (u_longlong_t)id);
-	(void) snprintf(snap3name, MAXNAMELEN, "%s@s3_%llu",
-	    clone1name, (u_longlong_t)id);
+	snap1name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	clone1name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	snap2name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	clone2name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	snap3name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+
+	(void) snprintf(snap1name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s@s1_%llu", osname, (u_longlong_t)id);
+	(void) snprintf(clone1name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s/c1_%llu", osname, (u_longlong_t)id);
+	(void) snprintf(snap2name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s@s2_%llu", clone1name, (u_longlong_t)id);
+	(void) snprintf(clone2name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s/c2_%llu", osname, (u_longlong_t)id);
+	(void) snprintf(snap3name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s@s3_%llu", clone1name, (u_longlong_t)id);
 
 	error = dsl_destroy_head(clone2name);
 	if (error && error != ENOENT)
@@ -3701,11 +3699,11 @@ ztest_dsl_dataset_cleanup(char *osname, uint64_t id)
 	if (error && error != ENOENT)
 		fatal(0, "dsl_destroy_snapshot(%s) = %d", snap1name, error);
 
-	umem_free(snap1name, MAXNAMELEN);
-	umem_free(clone1name, MAXNAMELEN);
-	umem_free(snap2name, MAXNAMELEN);
-	umem_free(clone2name, MAXNAMELEN);
-	umem_free(snap3name, MAXNAMELEN);
+	umem_free(snap1name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(clone1name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(snap2name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(clone2name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(snap3name, ZFS_MAX_DATASET_NAME_LEN);
 }
 
 /*
@@ -3723,26 +3721,26 @@ ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
 	char *osname = zd->zd_name;
 	int error;
 
-	snap1name  = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	clone1name = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	snap2name  = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	clone2name = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
-	snap3name  = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
+	snap1name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	clone1name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	snap2name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	clone2name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
+	snap3name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
 
 	(void) rw_rdlock(&ztest_name_lock);
 
 	ztest_dsl_dataset_cleanup(osname, id);
 
-	(void) snprintf(snap1name, MAXNAMELEN, "%s@s1_%llu",
-	    osname, (u_longlong_t)id);
-	(void) snprintf(clone1name, MAXNAMELEN, "%s/c1_%llu",
-	    osname, (u_longlong_t)id);
-	(void) snprintf(snap2name, MAXNAMELEN, "%s@s2_%llu",
-	    clone1name, (u_longlong_t)id);
-	(void) snprintf(clone2name, MAXNAMELEN, "%s/c2_%llu",
-	    osname, (u_longlong_t)id);
-	(void) snprintf(snap3name, MAXNAMELEN, "%s@s3_%llu",
-	    clone1name, (u_longlong_t)id);
+	(void) snprintf(snap1name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s@s1_%llu", osname, (u_longlong_t)id);
+	(void) snprintf(clone1name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s/c1_%llu", osname, (u_longlong_t)id);
+	(void) snprintf(snap2name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s@s2_%llu", clone1name, (u_longlong_t)id);
+	(void) snprintf(clone2name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s/c2_%llu", osname, (u_longlong_t)id);
+	(void) snprintf(snap3name, ZFS_MAX_DATASET_NAME_LEN,
+	    "%s@s3_%llu", clone1name, (u_longlong_t)id);
 
 	error = dmu_objset_snapshot_one(osname, strchr(snap1name, '@') + 1);
 	if (error && error != EEXIST) {
@@ -3808,11 +3806,11 @@ out:
 
 	(void) rw_unlock(&ztest_name_lock);
 
-	umem_free(snap1name, MAXNAMELEN);
-	umem_free(clone1name, MAXNAMELEN);
-	umem_free(snap2name, MAXNAMELEN);
-	umem_free(clone2name, MAXNAMELEN);
-	umem_free(snap3name, MAXNAMELEN);
+	umem_free(snap1name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(clone1name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(snap2name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(clone2name, ZFS_MAX_DATASET_NAME_LEN);
+	umem_free(snap3name, ZFS_MAX_DATASET_NAME_LEN);
 }
 
 #undef OD_ARRAY_SIZE
@@ -4622,7 +4620,7 @@ ztest_fzap(ztest_ds_t *zd, uint64_t id)
 	 * 2050 entries we should see ptrtbl growth and leaf-block split.
 	 */
 	for (i = 0; i < 2050; i++) {
-		char name[MAXNAMELEN];
+		char name[ZFS_MAX_DATASET_NAME_LEN];
 		uint64_t value = i;
 		dmu_tx_t *tx;
 		int error;
@@ -5077,7 +5075,7 @@ ztest_dmu_snapshot_hold(ztest_ds_t *zd, uint64_t id)
 	char fullname[100];
 	char clonename[100];
 	char tag[100];
-	char osname[MAXNAMELEN];
+	char osname[ZFS_MAX_DATASET_NAME_LEN];
 	nvlist_t *holds;
 
 	(void) rw_rdlock(&ztest_name_lock);
@@ -5964,13 +5962,13 @@ ztest_thread(void *arg)
 static void
 ztest_dataset_name(char *dsname, char *pool, int d)
 {
-	(void) snprintf(dsname, MAXNAMELEN, "%s/ds_%d", pool, d);
+	(void) snprintf(dsname, ZFS_MAX_DATASET_NAME_LEN, "%s/ds_%d", pool, d);
 }
 
 static void
 ztest_dataset_destroy(int d)
 {
-	char name[MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	int t;
 
 	ztest_dataset_name(name, ztest_opts.zo_pool, d);
@@ -6019,7 +6017,7 @@ ztest_dataset_open(int d)
 	uint64_t committed_seq = ZTEST_GET_SHARED_DS(d)->zd_seq;
 	objset_t *os;
 	zilog_t *zilog;
-	char name[MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	int error;
 
 	ztest_dataset_name(name, ztest_opts.zo_pool, d);
@@ -6256,8 +6254,8 @@ ztest_run(ztest_shared_t *zs)
 	 * different name.
 	 */
 	if (ztest_random(2) == 0) {
-		char name[MAXNAMELEN];
-		(void) snprintf(name, MAXNAMELEN, "%s_import",
+		char name[ZFS_MAX_DATASET_NAME_LEN];
+		(void) snprintf(name, sizeof (name), "%s_import",
 		    ztest_opts.zo_pool);
 		ztest_spa_import_export(ztest_opts.zo_pool, name);
 		ztest_spa_import_export(name, ztest_opts.zo_pool);
@@ -6834,7 +6832,7 @@ main(int argc, char **argv)
 		if (spa_open(ztest_opts.zo_pool, &spa, FTAG) == 0) {
 			spa_close(spa, FTAG);
 		} else {
-			char tmpname[MAXNAMELEN];
+			char tmpname[ZFS_MAX_DATASET_NAME_LEN];
 			kernel_fini();
 			kernel_init(FREAD | FWRITE);
 			(void) snprintf(tmpname, sizeof (tmpname), "%s_tmp",
diff --git a/cmd/zvol_id/zvol_id_main.c b/cmd/zvol_id/zvol_id_main.c
index 8f0504ae9..6bd5113f1 100644
--- a/cmd/zvol_id/zvol_id_main.c
+++ b/cmd/zvol_id/zvol_id_main.c
@@ -39,14 +39,14 @@ static int
 ioctl_get_msg(char *var, int fd)
 {
 	int error = 0;
-	char msg[ZFS_MAXNAMELEN];
+	char msg[ZFS_MAX_DATASET_NAME_LEN];
 
 	error = ioctl(fd, BLKZNAME, msg);
 	if (error < 0) {
 		return (error);
 	}
 
-	snprintf(var, ZFS_MAXNAMELEN, "%s", msg);
+	snprintf(var, ZFS_MAX_DATASET_NAME_LEN, "%s", msg);
 	return (error);
 }
 
@@ -54,7 +54,8 @@ int
 main(int argc, char **argv)
 {
 	int fd, error = 0;
-	char zvol_name[ZFS_MAXNAMELEN], zvol_name_part[ZFS_MAXNAMELEN];
+	char zvol_name[ZFS_MAX_DATASET_NAME_LEN];
+	char zvol_name_part[ZFS_MAX_DATASET_NAME_LEN];
 	char *dev_name;
 	struct stat64 statbuf;
 	int dev_minor, dev_part;
@@ -87,10 +88,11 @@ main(int argc, char **argv)
 		return (errno);
 	}
 	if (dev_part > 0)
-		snprintf(zvol_name_part, ZFS_MAXNAMELEN, "%s-part%d", zvol_name,
-		    dev_part);
+		snprintf(zvol_name_part, ZFS_MAX_DATASET_NAME_LEN,
+		    "%s-part%d", zvol_name, dev_part);
 	else
-		snprintf(zvol_name_part, ZFS_MAXNAMELEN, "%s", zvol_name);
+		snprintf(zvol_name_part, ZFS_MAX_DATASET_NAME_LEN,
+		    "%s", zvol_name);
 
 	for (i = 0; i < strlen(zvol_name_part); i++) {
 		if (isblank(zvol_name_part[i]))
diff --git a/config/kernel-kobj-name-len.m4 b/config/kernel-kobj-name-len.m4
deleted file mode 100644
index 37999fabb..000000000
--- a/config/kernel-kobj-name-len.m4
+++ /dev/null
@@ -1,21 +0,0 @@
-dnl #
-dnl # 2.6.27 API change,
-dnl # kobject KOBJ_NAME_LEN static limit removed.  All users of this
-dnl # constant were removed prior to 2.6.27, but to be on the safe
-dnl # side this check ensures the constant is undefined.
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_KOBJ_NAME_LEN], [
-	AC_MSG_CHECKING([whether kernel defines KOBJ_NAME_LEN])
-	ZFS_LINUX_TRY_COMPILE([
-		#include <linux/kobject.h>
-	],[
-		int val __attribute__ ((unused));
-		val = KOBJ_NAME_LEN;
-	],[
-		AC_MSG_RESULT([yes])
-		AC_DEFINE(HAVE_KOBJ_NAME_LEN, 1,
-		          [kernel defines KOBJ_NAME_LEN])
-	],[
-		AC_MSG_RESULT([no])
-	])
-])
diff --git a/config/kernel.m4 b/config/kernel.m4
index 800d782f1..086cd0b05 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -11,7 +11,6 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_BDEV_BLOCK_DEVICE_OPERATIONS
 	ZFS_AC_KERNEL_BLOCK_DEVICE_OPERATIONS_RELEASE_VOID
 	ZFS_AC_KERNEL_TYPE_FMODE_T
-	ZFS_AC_KERNEL_KOBJ_NAME_LEN
 	ZFS_AC_KERNEL_3ARG_BLKDEV_GET
 	ZFS_AC_KERNEL_BLKDEV_GET_BY_PATH
 	ZFS_AC_KERNEL_OPEN_BDEV_EXCLUSIVE
diff --git a/include/libzfs.h b/include/libzfs.h
index 40eb20781..f83e21423 100644
--- a/include/libzfs.h
+++ b/include/libzfs.h
@@ -49,8 +49,6 @@ extern "C" {
 /*
  * Miscellaneous ZFS constants
  */
-#define	ZFS_MAXNAMELEN		MAXNAMELEN
-#define	ZPOOL_MAXNAMELEN	MAXNAMELEN
 #define	ZFS_MAXPROPLEN		MAXPATHLEN
 #define	ZPOOL_MAXPROPLEN	MAXPATHLEN
 
diff --git a/include/libzfs_impl.h b/include/libzfs_impl.h
index 1efe4e233..36441ed7b 100644
--- a/include/libzfs_impl.h
+++ b/include/libzfs_impl.h
@@ -21,17 +21,17 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
  */
 
 #ifndef	_LIBZFS_IMPL_H
 #define	_LIBZFS_IMPL_H
 
-#include <sys/dmu.h>
 #include <sys/fs/zfs.h>
-#include <sys/zfs_ioctl.h>
 #include <sys/spa.h>
 #include <sys/nvpair.h>
+#include <sys/dmu.h>
+#include <sys/zfs_ioctl.h>
 
 #include <libuutil.h>
 #include <libzfs.h>
@@ -85,7 +85,7 @@ struct libzfs_handle {
 struct zfs_handle {
 	libzfs_handle_t *zfs_hdl;
 	zpool_handle_t *zpool_hdl;
-	char zfs_name[ZFS_MAXNAMELEN];
+	char zfs_name[ZFS_MAX_DATASET_NAME_LEN];
 	zfs_type_t zfs_type; /* type including snapshot */
 	zfs_type_t zfs_head_type; /* type excluding snapshot */
 	dmu_objset_stats_t zfs_dmustats;
@@ -106,7 +106,7 @@ struct zfs_handle {
 struct zpool_handle {
 	libzfs_handle_t *zpool_hdl;
 	zpool_handle_t *zpool_next;
-	char zpool_name[ZPOOL_MAXNAMELEN];
+	char zpool_name[ZFS_MAX_DATASET_NAME_LEN];
 	int zpool_state;
 	size_t zpool_config_size;
 	nvlist_t *zpool_config;
diff --git a/include/sys/dmu.h b/include/sys/dmu.h
index 74001d8f3..87a8a40eb 100644
--- a/include/sys/dmu.h
+++ b/include/sys/dmu.h
@@ -816,7 +816,7 @@ typedef struct dmu_objset_stats {
 	dmu_objset_type_t dds_type;
 	uint8_t dds_is_snapshot;
 	uint8_t dds_inconsistent;
-	char dds_origin[MAXNAMELEN];
+	char dds_origin[ZFS_MAX_DATASET_NAME_LEN];
 } dmu_objset_stats_t;
 
 /*
diff --git a/include/sys/dsl_dataset.h b/include/sys/dsl_dataset.h
index 195a271c9..4d2f5e418 100644
--- a/include/sys/dsl_dataset.h
+++ b/include/sys/dsl_dataset.h
@@ -227,7 +227,7 @@ typedef struct dsl_dataset {
 	uint8_t ds_feature_activation_needed[SPA_FEATURES];
 
 	/* Protected by ds_lock; keep at end of struct for better locality */
-	char ds_snapname[MAXNAMELEN];
+	char ds_snapname[ZFS_MAX_DATASET_NAME_LEN];
 } dsl_dataset_t;
 
 static inline dsl_dataset_phys_t *
@@ -262,6 +262,7 @@ int dsl_dataset_own_obj(struct dsl_pool *dp, uint64_t dsobj,
 void dsl_dataset_disown(dsl_dataset_t *ds, void *tag);
 void dsl_dataset_name(dsl_dataset_t *ds, char *name);
 boolean_t dsl_dataset_tryown(dsl_dataset_t *ds, void *tag);
+int dsl_dataset_namelen(dsl_dataset_t *ds);
 boolean_t dsl_dataset_has_owner(dsl_dataset_t *ds);
 uint64_t dsl_dataset_create_sync(dsl_dir_t *pds, const char *lastname,
     dsl_dataset_t *origin, uint64_t flags, cred_t *, dmu_tx_t *);
@@ -353,10 +354,10 @@ void dsl_dataset_deactivate_feature(uint64_t dsobj,
 #ifdef ZFS_DEBUG
 #define	dprintf_ds(ds, fmt, ...) do { \
 	if (zfs_flags & ZFS_DEBUG_DPRINTF) { \
-	char *__ds_name = kmem_alloc(MAXNAMELEN, KM_SLEEP); \
+	char *__ds_name = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP); \
 	dsl_dataset_name(ds, __ds_name); \
 	dprintf("ds=%s " fmt, __ds_name, __VA_ARGS__); \
-	kmem_free(__ds_name, MAXNAMELEN); \
+	kmem_free(__ds_name, ZFS_MAX_DATASET_NAME_LEN); \
 	} \
 _NOTE(CONSTCOND) } while (0)
 #else
diff --git a/include/sys/dsl_dir.h b/include/sys/dsl_dir.h
index a025c50a0..fb299684c 100644
--- a/include/sys/dsl_dir.h
+++ b/include/sys/dsl_dir.h
@@ -112,7 +112,7 @@ struct dsl_dir {
 	int64_t dd_space_towrite[TXG_SIZE];
 
 	/* protected by dd_lock; keep at end of struct for better locality */
-	char dd_myname[MAXNAMELEN];
+	char dd_myname[ZFS_MAX_DATASET_NAME_LEN];
 };
 
 static inline dsl_dir_phys_t *
@@ -176,11 +176,10 @@ boolean_t dsl_dir_is_zapified(dsl_dir_t *dd);
 #ifdef ZFS_DEBUG
 #define	dprintf_dd(dd, fmt, ...) do { \
 	if (zfs_flags & ZFS_DEBUG_DPRINTF) { \
-	char *__ds_name = kmem_alloc(MAXNAMELEN + strlen(MOS_DIR_NAME) + 1, \
-	    KM_SLEEP); \
+	char *__ds_name = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP); \
 	dsl_dir_name(dd, __ds_name); \
 	dprintf("dd=%s " fmt, __ds_name, __VA_ARGS__); \
-	kmem_free(__ds_name, MAXNAMELEN + strlen(MOS_DIR_NAME) + 1); \
+	kmem_free(__ds_name, ZFS_MAX_DATASET_NAME_LEN); \
 	} \
 _NOTE(CONSTCOND) } while (0)
 #else
diff --git a/include/sys/fs/zfs.h b/include/sys/fs/zfs.h
index e802454b9..b25d3016a 100644
--- a/include/sys/fs/zfs.h
+++ b/include/sys/fs/zfs.h
@@ -67,9 +67,13 @@ typedef enum dmu_objset_type {
 #define	ZFS_TYPE_DATASET	\
 	(ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME | ZFS_TYPE_SNAPSHOT)
 
+/*
+ * All of these include the terminating NUL byte.
+ */
 #define	ZAP_MAXNAMELEN 256
 #define	ZAP_MAXVALUELEN (1024 * 8)
 #define	ZAP_OLDMAXVALUELEN 1024
+#define	ZFS_MAX_DATASET_NAME_LEN 256
 
 /*
  * Dataset properties are identified by these constants and must be added to
@@ -1019,7 +1023,7 @@ typedef enum zfs_ioc {
 /*
  * zvol ioctl to get dataset name
  */
-#define	BLKZNAME		_IOR(0x12, 125, char[ZFS_MAXNAMELEN])
+#define	BLKZNAME		_IOR(0x12, 125, char[ZFS_MAX_DATASET_NAME_LEN])
 
 /*
  * Internal SPA load state.  Used by FMA diagnosis engine.
diff --git a/include/sys/spa_impl.h b/include/sys/spa_impl.h
index 2eb5fa12a..59cb44de2 100644
--- a/include/sys/spa_impl.h
+++ b/include/sys/spa_impl.h
@@ -126,7 +126,7 @@ struct spa {
 	/*
 	 * Fields protected by spa_namespace_lock.
 	 */
-	char		spa_name[MAXNAMELEN];	/* pool name */
+	char		spa_name[ZFS_MAX_DATASET_NAME_LEN];	/* pool name */
 	char		*spa_comment;		/* comment */
 	avl_node_t	spa_avl;		/* node in spa_namespace_avl */
 	nvlist_t	*spa_config;		/* last synced config */
diff --git a/include/sys/zap.h b/include/sys/zap.h
index 70cbaae97..700947397 100644
--- a/include/sys/zap.h
+++ b/include/sys/zap.h
@@ -363,7 +363,7 @@ typedef struct {
 	boolean_t za_normalization_conflict;
 	uint64_t za_num_integers;
 	uint64_t za_first_integer;	/* no sign extension for <8byte ints */
-	char za_name[MAXNAMELEN];
+	char za_name[ZAP_MAXNAMELEN];
 } zap_attribute_t;
 
 /*
diff --git a/include/sys/zfs_znode.h b/include/sys/zfs_znode.h
index 2c09feee1..8e563a572 100644
--- a/include/sys/zfs_znode.h
+++ b/include/sys/zfs_znode.h
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  */
 
 #ifndef	_SYS_FS_ZFS_ZNODE_H
@@ -139,17 +139,6 @@ extern "C" {
 #define	ZFS_SA_ATTRS		"SA_ATTRS"
 
 /*
- * Path component length
- *
- * The generic fs code uses MAXNAMELEN to represent
- * what the largest component length is.  Unfortunately,
- * this length includes the terminating NULL.  ZFS needs
- * to tell the users via pathconf() and statvfs() what the
- * true maximum length of a component is, excluding the NULL.
- */
-#define	ZFS_MAXNAMELEN	(MAXNAMELEN - 1)
-
-/*
  * Convert mode bits (zp_mode) to BSD-style DT_* values for storing in
  * the directory entries.  On Linux systems this value is already
  * defined correctly as part of the /usr/include/dirent.h header file.
diff --git a/lib/libzfs/libzfs_changelist.c b/lib/libzfs/libzfs_changelist.c
index 0bcfc0423..5e007c0f4 100644
--- a/lib/libzfs/libzfs_changelist.c
+++ b/lib/libzfs/libzfs_changelist.c
@@ -24,6 +24,7 @@
  * Use is subject to license terms.
  *
  * Portions Copyright 2007 Ramprakash Jelari
+ * Copyright (c) 2014, 2015 by Delphix. All rights reserved.
  */
 
 #include <libintl.h>
@@ -287,7 +288,7 @@ void
 changelist_rename(prop_changelist_t *clp, const char *src, const char *dst)
 {
 	prop_changenode_t *cn;
-	char newname[ZFS_MAXNAMELEN];
+	char newname[ZFS_MAX_DATASET_NAME_LEN];
 
 	for (cn = uu_list_first(clp->cl_list); cn != NULL;
 	    cn = uu_list_next(clp->cl_list, cn)) {
diff --git a/lib/libzfs/libzfs_dataset.c b/lib/libzfs/libzfs_dataset.c
index 80f75e256..3ff96f0c6 100644
--- a/lib/libzfs/libzfs_dataset.c
+++ b/lib/libzfs/libzfs_dataset.c
@@ -551,7 +551,7 @@ zfs_bookmark_exists(const char *path)
 {
 	nvlist_t *bmarks;
 	nvlist_t *props;
-	char fsname[ZFS_MAXNAMELEN];
+	char fsname[ZFS_MAX_DATASET_NAME_LEN];
 	char *bmark_name;
 	char *pound;
 	int err;
@@ -2201,7 +2201,7 @@ struct get_clones_arg {
 	uint64_t numclones;
 	nvlist_t *value;
 	const char *origin;
-	char buf[ZFS_MAXNAMELEN];
+	char buf[ZFS_MAX_DATASET_NAME_LEN];
 };
 
 int
@@ -2256,7 +2256,7 @@ zfs_get_clones_nvl(zfs_handle_t *zhp)
 
 		if (gca.numclones != 0) {
 			zfs_handle_t *root;
-			char pool[ZFS_MAXNAMELEN];
+			char pool[ZFS_MAX_DATASET_NAME_LEN];
 			char *cp = pool;
 
 			/* get the pool name */
@@ -3001,7 +3001,7 @@ check_parents(libzfs_handle_t *hdl, const char *path, uint64_t *zoned,
     boolean_t accept_ancestor, int *prefixlen)
 {
 	zfs_cmd_t zc = {"\0"};
-	char parent[ZFS_MAXNAMELEN];
+	char parent[ZFS_MAX_DATASET_NAME_LEN];
 	char *slash;
 	zfs_handle_t *zhp;
 	char errbuf[1024];
@@ -3240,7 +3240,7 @@ zfs_create(libzfs_handle_t *hdl, const char *path, zfs_type_t type,
 		ost = DMU_OST_ZFS;
 
 	/* open zpool handle for prop validation */
-	char pool_path[MAXNAMELEN];
+	char pool_path[ZFS_MAX_DATASET_NAME_LEN];
 	(void) strlcpy(pool_path, path, sizeof (pool_path));
 
 	/* truncate pool_path at first slash */
@@ -3309,7 +3309,7 @@ zfs_create(libzfs_handle_t *hdl, const char *path, zfs_type_t type,
 
 	/* check for failure */
 	if (ret != 0) {
-		char parent[ZFS_MAXNAMELEN];
+		char parent[ZFS_MAX_DATASET_NAME_LEN];
 		(void) parent_name(path, parent, sizeof (parent));
 
 		switch (errno) {
@@ -3399,7 +3399,7 @@ static int
 zfs_check_snap_cb(zfs_handle_t *zhp, void *arg)
 {
 	struct destroydata *dd = arg;
-	char name[ZFS_MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	int rv = 0;
 
 	(void) snprintf(name, sizeof (name),
@@ -3490,7 +3490,7 @@ zfs_destroy_snaps_nvl(libzfs_handle_t *hdl, nvlist_t *snaps, boolean_t defer)
 int
 zfs_clone(zfs_handle_t *zhp, const char *target, nvlist_t *props)
 {
-	char parent[ZFS_MAXNAMELEN];
+	char parent[ZFS_MAX_DATASET_NAME_LEN];
 	int ret;
 	char errbuf[1024];
 	libzfs_handle_t *hdl = zhp->zfs_hdl;
@@ -3620,7 +3620,7 @@ static int
 zfs_snapshot_cb(zfs_handle_t *zhp, void *arg)
 {
 	snapdata_t *sd = arg;
-	char name[ZFS_MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	int rv = 0;
 
 	if (zfs_prop_get_int(zhp, ZFS_PROP_INCONSISTENT) == 0) {
@@ -3669,7 +3669,7 @@ zfs_snapshot_nvl(libzfs_handle_t *hdl, nvlist_t *snaps, nvlist_t *props)
 	 * get pool handle for prop validation. assumes all snaps are in the
 	 * same pool, as does lzc_snapshot (below).
 	 */
-	char pool[MAXNAMELEN];
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
 	elem = nvlist_next_nvpair(snaps, NULL);
 	(void) strlcpy(pool, nvpair_name(elem), sizeof (pool));
 	pool[strcspn(pool, "/@")] = '\0';
@@ -3723,7 +3723,7 @@ zfs_snapshot(libzfs_handle_t *hdl, const char *path, boolean_t recursive,
 {
 	int ret;
 	snapdata_t sd = { 0 };
-	char fsname[ZFS_MAXNAMELEN];
+	char fsname[ZFS_MAX_DATASET_NAME_LEN];
 	char *cp;
 	zfs_handle_t *zhp;
 	char errbuf[1024];
@@ -3902,7 +3902,7 @@ zfs_rename(zfs_handle_t *zhp, const char *target, boolean_t recursive,
 	prop_changelist_t *cl = NULL;
 	zfs_handle_t *zhrp = NULL;
 	char *parentname = NULL;
-	char parent[ZFS_MAXNAMELEN];
+	char parent[ZFS_MAX_DATASET_NAME_LEN];
 	libzfs_handle_t *hdl = zhp->zfs_hdl;
 	char errbuf[1024];
 
@@ -4322,7 +4322,7 @@ zfs_userspace(zfs_handle_t *zhp, zfs_userquota_prop_t type,
 
 		zc.zc_nvlist_dst_size = sizeof (buf);
 		if (zfs_ioctl(hdl, ZFS_IOC_USERSPACE_MANY, &zc) != 0) {
-			char errbuf[ZFS_MAXNAMELEN + 32];
+			char errbuf[1024];
 
 			(void) snprintf(errbuf, sizeof (errbuf),
 			    dgettext(TEXT_DOMAIN,
@@ -4356,7 +4356,7 @@ static int
 zfs_hold_one(zfs_handle_t *zhp, void *arg)
 {
 	struct holdarg *ha = arg;
-	char name[ZFS_MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	int rv = 0;
 
 	(void) snprintf(name, sizeof (name),
@@ -4475,7 +4475,7 @@ static int
 zfs_release_one(zfs_handle_t *zhp, void *arg)
 {
 	struct holdarg *ha = arg;
-	char name[ZFS_MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	int rv = 0;
 	nvlist_t *existing_holds;
 
@@ -4604,7 +4604,7 @@ tryagain:
 	zc.zc_nvlist_dst_size = nvsz;
 	zc.zc_nvlist_dst = (uintptr_t)nvbuf;
 
-	(void) strlcpy(zc.zc_name, zhp->zfs_name, ZFS_MAXNAMELEN);
+	(void) strlcpy(zc.zc_name, zhp->zfs_name, sizeof (zc.zc_name));
 
 	if (ioctl(hdl->libzfs_fd, ZFS_IOC_GET_FSACL, &zc) != 0) {
 		(void) snprintf(errbuf, sizeof (errbuf),
diff --git a/lib/libzfs/libzfs_diff.c b/lib/libzfs/libzfs_diff.c
index c03603934..f5c799529 100644
--- a/lib/libzfs/libzfs_diff.c
+++ b/lib/libzfs/libzfs_diff.c
@@ -22,6 +22,7 @@
 /*
  * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2015 Nexenta Systems, Inc. All rights reserved.
+ * Copyright (c) 2015 by Delphix. All rights reserved.
  * Copyright 2016 Joyent, Inc.
  */
 
@@ -604,7 +605,7 @@ get_snapshot_names(differ_info_t *di, const char *fromsnap,
 		 * not the same dataset name, might be okay if
 		 * tosnap is a clone of a fromsnap descendant.
 		 */
-		char origin[ZFS_MAXNAMELEN];
+		char origin[ZFS_MAX_DATASET_NAME_LEN];
 		zprop_source_t src;
 		zfs_handle_t *zhp;
 
diff --git a/lib/libzfs/libzfs_iter.c b/lib/libzfs/libzfs_iter.c
index 5c1cf966a..96f657465 100644
--- a/lib/libzfs/libzfs_iter.c
+++ b/lib/libzfs/libzfs_iter.c
@@ -197,7 +197,7 @@ zfs_iter_bookmarks(zfs_handle_t *zhp, zfs_iter_f func, void *data)
 
 	for (pair = nvlist_next_nvpair(bmarks, NULL);
 	    pair != NULL; pair = nvlist_next_nvpair(bmarks, pair)) {
-		char name[ZFS_MAXNAMELEN];
+		char name[ZFS_MAX_DATASET_NAME_LEN];
 		char *bmark_name;
 		nvlist_t *bmark_props;
 
@@ -384,7 +384,7 @@ zfs_iter_snapspec(zfs_handle_t *fs_zhp, const char *spec_orig,
 			 * exists.
 			 */
 			if (ssa.ssa_last[0] != '\0') {
-				char snapname[ZFS_MAXNAMELEN];
+				char snapname[ZFS_MAX_DATASET_NAME_LEN];
 				(void) snprintf(snapname, sizeof (snapname),
 				    "%s@%s", zfs_get_name(fs_zhp),
 				    ssa.ssa_last);
@@ -404,7 +404,7 @@ zfs_iter_snapspec(zfs_handle_t *fs_zhp, const char *spec_orig,
 				ret = ENOENT;
 			}
 		} else {
-			char snapname[ZFS_MAXNAMELEN];
+			char snapname[ZFS_MAX_DATASET_NAME_LEN];
 			zfs_handle_t *snap_zhp;
 			(void) snprintf(snapname, sizeof (snapname), "%s@%s",
 			    zfs_get_name(fs_zhp), comma_separated);
diff --git a/lib/libzfs/libzfs_mount.c b/lib/libzfs/libzfs_mount.c
index 83351c716..5e57adab0 100644
--- a/lib/libzfs/libzfs_mount.c
+++ b/lib/libzfs/libzfs_mount.c
@@ -230,7 +230,7 @@ static boolean_t
 zfs_is_mountable(zfs_handle_t *zhp, char *buf, size_t buflen,
     zprop_source_t *source)
 {
-	char sourceloc[ZFS_MAXNAMELEN];
+	char sourceloc[MAXNAMELEN];
 	zprop_source_t sourcetype;
 
 	if (!zfs_prop_valid_for_type(ZFS_PROP_MOUNTPOINT, zhp->zfs_type,
diff --git a/lib/libzfs/libzfs_pool.c b/lib/libzfs/libzfs_pool.c
index 8b74e5da6..0a9780733 100644
--- a/lib/libzfs/libzfs_pool.c
+++ b/lib/libzfs/libzfs_pool.c
@@ -441,7 +441,7 @@ pool_uses_efi(nvlist_t *config)
 boolean_t
 zpool_is_bootable(zpool_handle_t *zhp)
 {
-	char bootfs[ZPOOL_MAXNAMELEN];
+	char bootfs[ZFS_MAX_DATASET_NAME_LEN];
 
 	return (zpool_get_prop(zhp, ZPOOL_PROP_BOOTFS, bootfs,
 	    sizeof (bootfs), NULL, B_FALSE) == 0 && strncmp(bootfs, "-",
@@ -4006,7 +4006,7 @@ zpool_obj_to_path(zpool_handle_t *zhp, uint64_t dsobj, uint64_t obj,
 	zfs_cmd_t zc = {"\0"};
 	boolean_t mounted = B_FALSE;
 	char *mntpnt = NULL;
-	char dsname[MAXNAMELEN];
+	char dsname[ZFS_MAX_DATASET_NAME_LEN];
 
 	if (dsobj == 0) {
 		/* special case for the MOS */
diff --git a/lib/libzfs/libzfs_sendrecv.c b/lib/libzfs/libzfs_sendrecv.c
index fdf9a115f..b38a2e544 100644
--- a/lib/libzfs/libzfs_sendrecv.c
+++ b/lib/libzfs/libzfs_sendrecv.c
@@ -837,7 +837,7 @@ typedef struct send_dump_data {
 	/* these are all just the short snapname (the part after the @) */
 	const char *fromsnap;
 	const char *tosnap;
-	char prevsnap[ZFS_MAXNAMELEN];
+	char prevsnap[ZFS_MAX_DATASET_NAME_LEN];
 	uint64_t prevsnap_obj;
 	boolean_t seenfrom, seento, replicate, doall, fromorigin;
 	boolean_t verbose, dryrun, parsable, progress, embed_data, std_out;
@@ -850,7 +850,7 @@ typedef struct send_dump_data {
 	snapfilter_cb_t *filter_cb;
 	void *filter_cb_arg;
 	nvlist_t *debugnv;
-	char holdtag[ZFS_MAXNAMELEN];
+	char holdtag[ZFS_MAX_DATASET_NAME_LEN];
 	int cleanup_fd;
 	uint64_t size;
 } send_dump_data_t;
@@ -1485,7 +1485,7 @@ zfs_send_resume(libzfs_handle_t *hdl, sendflags_t *flags, int outfd,
 	uint64_t resumeobj, resumeoff, toguid, fromguid, bytes;
 	zfs_handle_t *zhp;
 	int error = 0;
-	char name[ZFS_MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	enum lzc_send_flags lzc_flags = 0;
 
 	(void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
@@ -2076,8 +2076,8 @@ recv_rename(libzfs_handle_t *hdl, const char *name, const char *tryname,
 	if (err != 0 && strncmp(name + baselen, "recv-", 5) != 0) {
 		seq++;
 
-		(void) snprintf(newname, ZFS_MAXNAMELEN, "%.*srecv-%u-%u",
-		    baselen, name, getpid(), seq);
+		(void) snprintf(newname, ZFS_MAX_DATASET_NAME_LEN,
+		    "%.*srecv-%u-%u", baselen, name, getpid(), seq);
 		(void) strlcpy(zc.zc_value, newname, sizeof (zc.zc_value));
 
 		if (flags->verbose) {
@@ -2205,7 +2205,7 @@ static int
 guid_to_name(libzfs_handle_t *hdl, const char *parent, uint64_t guid,
     boolean_t bookmark_ok, char *name)
 {
-	char pname[ZFS_MAXNAMELEN];
+	char pname[ZFS_MAX_DATASET_NAME_LEN];
 	guid_to_name_data_t gtnd;
 
 	gtnd.guid = guid;
@@ -2260,7 +2260,7 @@ created_before(libzfs_handle_t *hdl, avl_tree_t *avl,
 {
 	nvlist_t *nvfs;
 	char *fsname = NULL, *snapname = NULL;
-	char buf[ZFS_MAXNAMELEN];
+	char buf[ZFS_MAX_DATASET_NAME_LEN];
 	int rv;
 	zfs_handle_t *guid1hdl, *guid2hdl;
 	uint64_t create1, create2;
@@ -2311,7 +2311,7 @@ recv_incremental_replication(libzfs_handle_t *hdl, const char *tofs,
 	avl_tree_t *local_avl;
 	nvpair_t *fselem, *nextfselem;
 	char *fromsnap;
-	char newname[ZFS_MAXNAMELEN];
+	char newname[ZFS_MAX_DATASET_NAME_LEN];
 	char guidname[32];
 	int error;
 	boolean_t needagain, progress, recursive;
@@ -2430,7 +2430,7 @@ again:
 
 			/* check for delete */
 			if (found == NULL) {
-				char name[ZFS_MAXNAMELEN];
+				char name[ZFS_MAX_DATASET_NAME_LEN];
 
 				if (!flags->force)
 					continue;
@@ -2471,8 +2471,8 @@ again:
 			/* check for different snapname */
 			if (strcmp(nvpair_name(snapelem),
 			    stream_snapname) != 0) {
-				char name[ZFS_MAXNAMELEN];
-				char tryname[ZFS_MAXNAMELEN];
+				char name[ZFS_MAX_DATASET_NAME_LEN];
+				char tryname[ZFS_MAX_DATASET_NAME_LEN];
 
 				(void) snprintf(name, sizeof (name), "%s@%s",
 				    fsname, nvpair_name(snapelem));
@@ -2556,7 +2556,7 @@ again:
 		    ((flags->isprefix || strcmp(tofs, fsname) != 0) &&
 		    (s1 != NULL) && (s2 != NULL) && strcmp(s1, s2) != 0)) {
 			nvlist_t *parent;
-			char tryname[ZFS_MAXNAMELEN];
+			char tryname[ZFS_MAX_DATASET_NAME_LEN];
 
 			parent = fsavl_find(local_avl,
 			    stream_parent_fromsnap_guid, NULL);
@@ -2624,8 +2624,8 @@ zfs_receive_package(libzfs_handle_t *hdl, int fd, const char *destname,
 	char *fromsnap = NULL;
 	char *sendsnap = NULL;
 	char *cp;
-	char tofs[ZFS_MAXNAMELEN];
-	char sendfs[ZFS_MAXNAMELEN];
+	char tofs[ZFS_MAX_DATASET_NAME_LEN];
+	char sendfs[ZFS_MAX_DATASET_NAME_LEN];
 	char errbuf[1024];
 	dmu_replay_record_t drre;
 	int error;
@@ -2709,7 +2709,7 @@ zfs_receive_package(libzfs_handle_t *hdl, int fd, const char *destname,
 			nvlist_t *renamed = NULL;
 			nvpair_t *pair = NULL;
 
-			(void) strlcpy(tofs, destname, ZFS_MAXNAMELEN);
+			(void) strlcpy(tofs, destname, sizeof (tofs));
 			if (flags->isprefix) {
 				struct drr_begin *drrb = &drr->drr_u.drr_begin;
 				int i;
@@ -2718,7 +2718,7 @@ zfs_receive_package(libzfs_handle_t *hdl, int fd, const char *destname,
 					cp = strrchr(drrb->drr_toname, '/');
 					if (cp == NULL) {
 						(void) strlcat(tofs, "/",
-						    ZFS_MAXNAMELEN);
+						    sizeof (tofs));
 						i = 0;
 					} else {
 						i = (cp - drrb->drr_toname);
@@ -2728,7 +2728,7 @@ zfs_receive_package(libzfs_handle_t *hdl, int fd, const char *destname,
 				}
 				/* zfs_receive_one() will create_parents() */
 				(void) strlcat(tofs, &drrb->drr_toname[i],
-				    ZFS_MAXNAMELEN);
+				    sizeof (tofs));
 				*strchr(tofs, '@') = '\0';
 			}
 
@@ -2770,7 +2770,7 @@ zfs_receive_package(libzfs_handle_t *hdl, int fd, const char *destname,
 	 * zfs_receive_one().
 	 */
 	(void) strlcpy(sendfs, drr->drr_u.drr_begin.drr_toname,
-	    ZFS_MAXNAMELEN);
+	    sizeof (sendfs));
 	if ((cp = strchr(sendfs, '@')) != NULL) {
 		*cp = '\0';
 		/*
@@ -2920,7 +2920,7 @@ static void
 recv_ecksum_set_aux(libzfs_handle_t *hdl, const char *target_snap,
     boolean_t resumable)
 {
-	char target_fs[ZFS_MAXNAMELEN];
+	char target_fs[ZFS_MAX_DATASET_NAME_LEN];
 
 	zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
 	    "checksum mismatch or incomplete stream"));
@@ -3113,7 +3113,7 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 		if (flags->verbose)
 			(void) printf("found clone origin %s\n", origin);
 	} else if (originsnap) {
-		(void) strncpy(origin, originsnap, ZFS_MAXNAMELEN);
+		(void) strncpy(origin, originsnap, sizeof (origin));
 		if (flags->verbose)
 			(void) printf("using provided clone origin %s\n",
 			    origin);
@@ -3138,7 +3138,7 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 			*cp = '\0';
 		if (cp &&
 		    !zfs_dataset_exists(hdl, name, ZFS_TYPE_DATASET)) {
-			char suffix[ZFS_MAXNAMELEN];
+			char suffix[ZFS_MAX_DATASET_NAME_LEN];
 			(void) strcpy(suffix, strrchr(destsnap, '/'));
 			if (guid_to_name(hdl, name, parent_snapguid,
 			    B_FALSE, destsnap) == 0) {
@@ -3165,7 +3165,7 @@ zfs_receive_one(libzfs_handle_t *hdl, int infd, const char *tosnap,
 		if ((flags->isprefix || (*(chopprefix = drrb->drr_toname +
 		    strlen(sendfs)) != '\0' && *chopprefix != '@')) &&
 		    !zfs_dataset_exists(hdl, name, ZFS_TYPE_DATASET)) {
-			char snap[ZFS_MAXNAMELEN];
+			char snap[ZFS_MAX_DATASET_NAME_LEN];
 			(void) strcpy(snap, strchr(destsnap, '@'));
 			if (guid_to_name(hdl, name, drrb->drr_fromguid,
 			    B_FALSE, destsnap) == 0) {
@@ -3609,7 +3609,7 @@ zfs_receive_impl(libzfs_handle_t *hdl, const char *tosnap,
 	}
 
 	if (DMU_GET_STREAM_HDRTYPE(drrb->drr_versioninfo) == DMU_SUBSTREAM) {
-		char nonpackage_sendfs[ZFS_MAXNAMELEN];
+		char nonpackage_sendfs[ZFS_MAX_DATASET_NAME_LEN];
 		if (sendfs == NULL) {
 			/*
 			 * We were not called from zfs_receive_package(). Get
@@ -3617,7 +3617,8 @@ zfs_receive_impl(libzfs_handle_t *hdl, const char *tosnap,
 			 */
 			char *cp;
 			(void) strlcpy(nonpackage_sendfs,
-			    drr.drr_u.drr_begin.drr_toname, ZFS_MAXNAMELEN);
+			    drr.drr_u.drr_begin.drr_toname,
+			    sizeof (nonpackage_sendfs));
 			if ((cp = strchr(nonpackage_sendfs, '@')) != NULL)
 				*cp = '\0';
 			sendfs = nonpackage_sendfs;
diff --git a/lib/libzfs_core/libzfs_core.c b/lib/libzfs_core/libzfs_core.c
index e20e58dba..0359e4284 100644
--- a/lib/libzfs_core/libzfs_core.c
+++ b/lib/libzfs_core/libzfs_core.c
@@ -217,7 +217,7 @@ lzc_snapshot(nvlist_t *snaps, nvlist_t *props, nvlist_t **errlist)
 	nvpair_t *elem;
 	nvlist_t *args;
 	int error;
-	char pool[MAXNAMELEN];
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
 
 	*errlist = NULL;
 
@@ -269,7 +269,7 @@ lzc_destroy_snaps(nvlist_t *snaps, boolean_t defer, nvlist_t **errlist)
 	nvpair_t *elem;
 	nvlist_t *args;
 	int error;
-	char pool[MAXNAMELEN];
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
 
 	/* determine the pool name */
 	elem = nvlist_next_nvpair(snaps, NULL);
@@ -296,7 +296,7 @@ lzc_snaprange_space(const char *firstsnap, const char *lastsnap,
 	nvlist_t *args;
 	nvlist_t *result;
 	int err;
-	char fs[MAXNAMELEN];
+	char fs[ZFS_MAX_DATASET_NAME_LEN];
 	char *atp;
 
 	/* determine the fs name */
@@ -361,7 +361,7 @@ lzc_exists(const char *dataset)
 int
 lzc_hold(nvlist_t *holds, int cleanup_fd, nvlist_t **errlist)
 {
-	char pool[MAXNAMELEN];
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
 	nvlist_t *args;
 	nvpair_t *elem;
 	int error;
@@ -408,7 +408,7 @@ lzc_hold(nvlist_t *holds, int cleanup_fd, nvlist_t **errlist)
 int
 lzc_release(nvlist_t *holds, nvlist_t **errlist)
 {
-	char pool[MAXNAMELEN];
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
 	nvpair_t *elem;
 
 	/* determine the pool name */
@@ -842,7 +842,7 @@ lzc_bookmark(nvlist_t *bookmarks, nvlist_t **errlist)
 {
 	nvpair_t *elem;
 	int error;
-	char pool[MAXNAMELEN];
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
 
 	/* determine the pool name */
 	elem = nvlist_next_nvpair(bookmarks, NULL);
@@ -904,7 +904,7 @@ lzc_destroy_bookmarks(nvlist_t *bmarks, nvlist_t **errlist)
 {
 	nvpair_t *elem;
 	int error;
-	char pool[MAXNAMELEN];
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
 
 	/* determine the pool name */
 	elem = nvlist_next_nvpair(bmarks, NULL);
diff --git a/module/zcommon/zfs_namecheck.c b/module/zcommon/zfs_namecheck.c
index ff724be58..b58071bed 100644
--- a/module/zcommon/zfs_namecheck.c
+++ b/module/zcommon/zfs_namecheck.c
@@ -69,7 +69,7 @@ zfs_component_namecheck(const char *path, namecheck_err_t *why, char *what)
 {
 	const char *loc;
 
-	if (strlen(path) >= MAXNAMELEN) {
+	if (strlen(path) >= ZFS_MAX_DATASET_NAME_LEN) {
 		if (why)
 			*why = NAME_ERR_TOOLONG;
 		return (-1);
@@ -140,27 +140,8 @@ dataset_namecheck(const char *path, namecheck_err_t *why, char *what)
 
 	/*
 	 * Make sure the name is not too long.
-	 *
-	 * ZFS_MAXNAMELEN is the maximum dataset length used in the userland
-	 * which is the same as MAXNAMELEN used in the kernel.
-	 * If ZFS_MAXNAMELEN value is changed, make sure to cleanup all
-	 * places using MAXNAMELEN.
-	 *
-	 * When HAVE_KOBJ_NAME_LEN is defined the maximum safe kobject name
-	 * length is 20 bytes.  This 20 bytes is broken down as follows to
-	 * provide a maximum safe <pool>/<dataset>[@snapshot] length of only
-	 * 18 bytes.  To ensure bytes are left for <dataset>[@snapshot] the
-	 * <pool> portition is futher limited to 9 bytes.  For 2.6.27 and
-	 * newer kernels this limit is set to MAXNAMELEN.
-	 *
-	 *   <pool>/<dataset> + <partition> + <newline>
-	 *   (18)             + (1)         + (1)
 	 */
-#ifdef HAVE_KOBJ_NAME_LEN
-	if (strlen(path) > 18) {
-#else
-	if (strlen(path) >= MAXNAMELEN) {
-#endif /* HAVE_KOBJ_NAME_LEN */
+	if (strlen(path) >= ZFS_MAX_DATASET_NAME_LEN) {
 		if (why)
 			*why = NAME_ERR_TOOLONG;
 		return (-1);
@@ -289,7 +270,7 @@ mountpoint_namecheck(const char *path, namecheck_err_t *why)
 		while (*end != '/' && *end != '\0')
 			end++;
 
-		if (end - start >= MAXNAMELEN) {
+		if (end - start >= ZFS_MAX_DATASET_NAME_LEN) {
 			if (why)
 				*why = NAME_ERR_TOOLONG;
 			return (-1);
@@ -314,27 +295,8 @@ pool_namecheck(const char *pool, namecheck_err_t *why, char *what)
 
 	/*
 	 * Make sure the name is not too long.
-	 *
-	 * ZPOOL_MAXNAMELEN is the maximum pool length used in the userland
-	 * which is the same as MAXNAMELEN used in the kernel.
-	 * If ZPOOL_MAXNAMELEN value is changed, make sure to cleanup all
-	 * places using MAXNAMELEN.
-	 *
-	 * When HAVE_KOBJ_NAME_LEN is defined the maximum safe kobject name
-	 * length is 20 bytes.  This 20 bytes is broken down as follows to
-	 * provide a maximum safe <pool>/<dataset>[@snapshot] length of only
-	 * 18 bytes.  To ensure bytes are left for <dataset>[@snapshot] the
-	 * <pool> portition is futher limited to 8 bytes.  For 2.6.27 and
-	 * newer kernels this limit is set to MAXNAMELEN.
-	 *
-	 *   <pool>/<dataset> + <partition> + <newline>
-	 *   (18)             + (1)         + (1)
 	 */
-#ifdef HAVE_KOBJ_NAME_LEN
-	if (strlen(pool) > 8) {
-#else
-	if (strlen(pool) >= MAXNAMELEN) {
-#endif /* HAVE_KOBJ_NAME_LEN */
+	if (strlen(pool) >= ZFS_MAX_DATASET_NAME_LEN) {
 		if (why)
 			*why = NAME_ERR_TOOLONG;
 		return (-1);
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index a9991aabb..22ca84d96 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -671,7 +671,7 @@ dmu_objset_refresh_ownership(objset_t *os, void *tag)
 {
 	dsl_pool_t *dp;
 	dsl_dataset_t *ds, *newds;
-	char name[MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 
 	ds = os->os_dsl_dataset;
 	VERIFY3P(ds, !=, NULL);
@@ -895,6 +895,9 @@ dmu_objset_create_check(void *arg, dmu_tx_t *tx)
 	if (strchr(doca->doca_name, '@') != NULL)
 		return (SET_ERROR(EINVAL));
 
+	if (strlen(doca->doca_name) >= ZFS_MAX_DATASET_NAME_LEN)
+		return (SET_ERROR(ENAMETOOLONG));
+
 	error = dsl_dir_hold(dp, doca->doca_name, FTAG, &pdd, &tail);
 	if (error != 0)
 		return (error);
@@ -981,6 +984,9 @@ dmu_objset_clone_check(void *arg, dmu_tx_t *tx)
 	if (strchr(doca->doca_clone, '@') != NULL)
 		return (SET_ERROR(EINVAL));
 
+	if (strlen(doca->doca_clone) >= ZFS_MAX_DATASET_NAME_LEN)
+		return (SET_ERROR(ENAMETOOLONG));
+
 	error = dsl_dir_hold(dp, doca->doca_clone, FTAG, &pdd, &tail);
 	if (error != 0)
 		return (error);
@@ -1020,7 +1026,7 @@ dmu_objset_clone_sync(void *arg, dmu_tx_t *tx)
 	const char *tail;
 	dsl_dataset_t *origin, *ds;
 	uint64_t obj;
-	char namebuf[MAXNAMELEN];
+	char namebuf[ZFS_MAX_DATASET_NAME_LEN];
 
 	VERIFY0(dsl_dir_hold(dp, doca->doca_clone, FTAG, &pdd, &tail));
 	VERIFY0(dsl_dataset_hold(dp, doca->doca_origin, FTAG, &origin));
@@ -2047,7 +2053,7 @@ dmu_objset_get_user(objset_t *os)
 
 /*
  * Determine name of filesystem, given name of snapshot.
- * buf must be at least MAXNAMELEN bytes
+ * buf must be at least ZFS_MAX_DATASET_NAME_LEN bytes
  */
 int
 dmu_fsname(const char *snapname, char *buf)
@@ -2055,7 +2061,7 @@ dmu_fsname(const char *snapname, char *buf)
 	char *atp = strchr(snapname, '@');
 	if (atp == NULL)
 		return (SET_ERROR(EINVAL));
-	if (atp - snapname >= MAXNAMELEN)
+	if (atp - snapname >= ZFS_MAX_DATASET_NAME_LEN)
 		return (SET_ERROR(ENAMETOOLONG));
 	(void) strlcpy(buf, snapname, atp - snapname + 1);
 	return (0);
diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index 2f4087a67..80f7dc1aa 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -1356,7 +1356,7 @@ dmu_recv_begin_check(void *arg, dmu_tx_t *tx)
 		dsl_dataset_rele(ds, FTAG);
 	} else if (error == ENOENT) {
 		/* target fs does not exist; must be a full backup or clone */
-		char buf[MAXNAMELEN];
+		char buf[ZFS_MAX_DATASET_NAME_LEN];
 
 		/*
 		 * If it's a non-clone incremental, we are missing the
@@ -1376,7 +1376,7 @@ dmu_recv_begin_check(void *arg, dmu_tx_t *tx)
 			return (SET_ERROR(EINVAL));
 
 		/* Open the parent of tofs */
-		ASSERT3U(strlen(tofs), <, MAXNAMELEN);
+		ASSERT3U(strlen(tofs), <, sizeof (buf));
 		(void) strlcpy(buf, tofs, strrchr(tofs, '/') - tofs + 1);
 		error = dsl_dataset_hold(dp, buf, FTAG, &ds);
 		if (error != 0)
@@ -1533,9 +1533,11 @@ dmu_recv_resume_begin_check(void *arg, dmu_tx_t *tx)
 	uint64_t featureflags = DMU_GET_FEATUREFLAGS(drrb->drr_versioninfo);
 	dsl_dataset_t *ds;
 	const char *tofs = drba->drba_cookie->drc_tofs;
-	char recvname[ZFS_MAXNAMELEN];
 	uint64_t val;
 
+	/* 6 extra bytes for /%recv */
+	char recvname[ZFS_MAX_DATASET_NAME_LEN + 6];
+
 	/* already checked */
 	ASSERT3U(drrb->drr_magic, ==, DMU_BACKUP_MAGIC);
 	ASSERT(featureflags & DMU_BACKUP_FEATURE_RESUMING);
@@ -1633,7 +1635,8 @@ dmu_recv_resume_begin_sync(void *arg, dmu_tx_t *tx)
 	const char *tofs = drba->drba_cookie->drc_tofs;
 	dsl_dataset_t *ds;
 	uint64_t dsobj;
-	char recvname[ZFS_MAXNAMELEN];
+	/* 6 extra bytes for /%recv */
+	char recvname[ZFS_MAX_DATASET_NAME_LEN + 6];
 
 	(void) snprintf(recvname, sizeof (recvname), "%s/%s",
 	    tofs, recv_clone_name);
@@ -2359,7 +2362,7 @@ dmu_recv_cleanup_ds(dmu_recv_cookie_t *drc)
 		txg_wait_synced(drc->drc_ds->ds_dir->dd_pool, 0);
 		dsl_dataset_disown(drc->drc_ds, dmu_recv_tag);
 	} else {
-		char name[MAXNAMELEN];
+		char name[ZFS_MAX_DATASET_NAME_LEN];
 		dsl_dataset_name(drc->drc_ds, name);
 		dsl_dataset_disown(drc->drc_ds, dmu_recv_tag);
 		(void) dsl_destroy_head(name);
@@ -3191,16 +3194,13 @@ dmu_recv_existing_end(dmu_recv_cookie_t *drc)
 	int error;
 
 #ifdef _KERNEL
-	char *name;
-
 	/*
 	 * We will be destroying the ds; make sure its origin is unmounted if
 	 * necessary.
 	 */
-	name = kmem_alloc(MAXNAMELEN, KM_SLEEP);
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 	dsl_dataset_name(drc->drc_ds, name);
 	zfs_destroy_unmount_origin(name);
-	kmem_free(name, MAXNAMELEN);
 #endif
 
 	error = dsl_sync_task(drc->drc_tofs,
diff --git a/module/zfs/dsl_bookmark.c b/module/zfs/dsl_bookmark.c
index 447a3a2dc..5a7f034ce 100644
--- a/module/zfs/dsl_bookmark.c
+++ b/module/zfs/dsl_bookmark.c
@@ -34,10 +34,10 @@ static int
 dsl_bookmark_hold_ds(dsl_pool_t *dp, const char *fullname,
     dsl_dataset_t **dsp, void *tag, char **shortnamep)
 {
-	char buf[MAXNAMELEN];
+	char buf[ZFS_MAX_DATASET_NAME_LEN];
 	char *hashp;
 
-	if (strlen(fullname) >= MAXNAMELEN)
+	if (strlen(fullname) >= ZFS_MAX_DATASET_NAME_LEN)
 		return (SET_ERROR(ENAMETOOLONG));
 	hashp = strchr(fullname, '#');
 	if (hashp == NULL)
diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index 3d1115e31..5b7de74dc 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -670,22 +670,38 @@ dsl_dataset_name(dsl_dataset_t *ds, char *name)
 		dsl_dir_name(ds->ds_dir, name);
 		VERIFY0(dsl_dataset_get_snapname(ds));
 		if (ds->ds_snapname[0]) {
-			(void) strcat(name, "@");
+			VERIFY3U(strlcat(name, "@", ZFS_MAX_DATASET_NAME_LEN),
+			    <, ZFS_MAX_DATASET_NAME_LEN);
 			/*
 			 * We use a "recursive" mutex so that we
 			 * can call dprintf_ds() with ds_lock held.
 			 */
 			if (!MUTEX_HELD(&ds->ds_lock)) {
 				mutex_enter(&ds->ds_lock);
-				(void) strcat(name, ds->ds_snapname);
+				VERIFY3U(strlcat(name, ds->ds_snapname,
+				    ZFS_MAX_DATASET_NAME_LEN), <,
+				    ZFS_MAX_DATASET_NAME_LEN);
 				mutex_exit(&ds->ds_lock);
 			} else {
-				(void) strcat(name, ds->ds_snapname);
+				VERIFY3U(strlcat(name, ds->ds_snapname,
+				    ZFS_MAX_DATASET_NAME_LEN), <,
+				    ZFS_MAX_DATASET_NAME_LEN);
 			}
 		}
 	}
 }
 
+int
+dsl_dataset_namelen(dsl_dataset_t *ds)
+{
+	int len;
+	VERIFY0(dsl_dataset_get_snapname(ds));
+	mutex_enter(&ds->ds_lock);
+	len = dsl_dir_namelen(ds->ds_dir) + 1 + strlen(ds->ds_snapname);
+	mutex_exit(&ds->ds_lock);
+	return (len);
+}
+
 void
 dsl_dataset_rele(dsl_dataset_t *ds, void *tag)
 {
@@ -1255,10 +1271,10 @@ dsl_dataset_snapshot_check(void *arg, dmu_tx_t *tx)
 		int error = 0;
 		dsl_dataset_t *ds;
 		char *name, *atp;
-		char dsname[MAXNAMELEN];
+		char dsname[ZFS_MAX_DATASET_NAME_LEN];
 
 		name = nvpair_name(pair);
-		if (strlen(name) >= MAXNAMELEN)
+		if (strlen(name) >= ZFS_MAX_DATASET_NAME_LEN)
 			error = SET_ERROR(ENAMETOOLONG);
 		if (error == 0) {
 			atp = strchr(name, '@');
@@ -1431,7 +1447,7 @@ dsl_dataset_snapshot_sync(void *arg, dmu_tx_t *tx)
 	    pair != NULL; pair = nvlist_next_nvpair(ddsa->ddsa_snaps, pair)) {
 		dsl_dataset_t *ds;
 		char *name, *atp;
-		char dsname[MAXNAMELEN];
+		char dsname[ZFS_MAX_DATASET_NAME_LEN];
 
 		name = nvpair_name(pair);
 		atp = strchr(name, '@');
@@ -1478,7 +1494,7 @@ dsl_dataset_snapshot(nvlist_t *snaps, nvlist_t *props, nvlist_t *errors)
 		suspended = fnvlist_alloc();
 		for (pair = nvlist_next_nvpair(snaps, NULL); pair != NULL;
 		    pair = nvlist_next_nvpair(snaps, pair)) {
-			char fsname[MAXNAMELEN];
+			char fsname[ZFS_MAX_DATASET_NAME_LEN];
 			char *snapname = nvpair_name(pair);
 			char *atp;
 			void *cookie;
@@ -1687,7 +1703,7 @@ get_clones_stat(dsl_dataset_t *ds, nvlist_t *nv)
 	    zap_cursor_retrieve(&zc, &za) == 0;
 	    zap_cursor_advance(&zc)) {
 		dsl_dataset_t *clone;
-		char buf[ZFS_MAXNAMELEN];
+		char buf[ZFS_MAX_DATASET_NAME_LEN];
 		VERIFY0(dsl_dataset_hold_obj(ds->ds_dir->dd_pool,
 		    za.za_first_integer, FTAG, &clone));
 		dsl_dir_name(clone->ds_dir, buf);
@@ -1797,7 +1813,7 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
 		get_clones_stat(ds, nv);
 	} else {
 		if (ds->ds_prev != NULL && ds->ds_prev != dp->dp_origin_snap) {
-			char buf[MAXNAMELEN];
+			char buf[ZFS_MAX_DATASET_NAME_LEN];
 			dsl_dataset_name(ds->ds_prev, buf);
 			dsl_prop_nvlist_add_string(nv, ZFS_PROP_PREV_SNAP, buf);
 		}
@@ -1848,8 +1864,9 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
 	}
 
 	if (!dsl_dataset_is_snapshot(ds)) {
+		/* 6 extra bytes for /%recv */
+		char recvname[ZFS_MAX_DATASET_NAME_LEN + 6];
 		dsl_dataset_t *recv_ds;
-		char recvname[ZFS_MAXNAMELEN];
 
 		/*
 		 * A failed "newfs" (e.g. full) resumable receive leaves
@@ -1863,9 +1880,11 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
 		 * for the prop.
 		 */
 		dsl_dataset_name(ds, recvname);
-		(void) strcat(recvname, "/");
-		(void) strcat(recvname, recv_clone_name);
-		if (dsl_dataset_hold(dp, recvname, FTAG, &recv_ds) == 0) {
+		if (strlcat(recvname, "/", sizeof (recvname)) <
+		    sizeof (recvname) &&
+		    strlcat(recvname, recv_clone_name, sizeof (recvname)) <
+		    sizeof (recvname) &&
+		    dsl_dataset_hold(dp, recvname, FTAG, &recv_ds) == 0) {
 			get_receive_resume_stats(recv_ds, nv);
 			dsl_dataset_rele(recv_ds, FTAG);
 		}
@@ -1990,7 +2009,7 @@ dsl_dataset_rename_snapshot_check_impl(dsl_pool_t *dp,
 
 	/* dataset name + 1 for the "@" + the new snapshot name must fit */
 	if (dsl_dir_namelen(hds->ds_dir) + 1 +
-	    strlen(ddrsa->ddrsa_newsnapname) >= MAXNAMELEN)
+	    strlen(ddrsa->ddrsa_newsnapname) >= ZFS_MAX_DATASET_NAME_LEN)
 		error = SET_ERROR(ENAMETOOLONG);
 
 	return (error);
@@ -2223,7 +2242,7 @@ dsl_dataset_rollback_sync(void *arg, dmu_tx_t *tx)
 	dsl_pool_t *dp = dmu_tx_pool(tx);
 	dsl_dataset_t *ds, *clone;
 	uint64_t cloneobj;
-	char namebuf[ZFS_MAXNAMELEN];
+	char namebuf[ZFS_MAX_DATASET_NAME_LEN];
 
 	VERIFY0(dsl_dataset_hold(dp, ddra->ddra_fsname, FTAG, &ds));
 
@@ -2776,7 +2795,7 @@ promote_rele(dsl_dataset_promote_arg_t *ddpa, void *tag)
  * Promote a clone.
  *
  * If it fails due to a conflicting snapshot name, "conflsnap" will be filled
- * in with the name.  (It must be at least MAXNAMELEN bytes long.)
+ * in with the name.  (It must be at least ZFS_MAX_DATASET_NAME_LEN bytes long.)
  */
 int
 dsl_dataset_promote(const char *name, char *conflsnap)
diff --git a/module/zfs/dsl_deleg.c b/module/zfs/dsl_deleg.c
index 952422be2..eb39cff57 100644
--- a/module/zfs/dsl_deleg.c
+++ b/module/zfs/dsl_deleg.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
  */
 
 /*
@@ -330,7 +330,7 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
 	za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
 	basezc = kmem_alloc(sizeof (zap_cursor_t), KM_SLEEP);
 	baseza = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
-	source = kmem_alloc(MAXNAMELEN + strlen(MOS_DIR_NAME) + 1, KM_SLEEP);
+	source = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 	VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
 
 	for (dd = startdd; dd != NULL; dd = dd->dd_parent) {
@@ -370,7 +370,7 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
 		nvlist_free(sp_nvp);
 	}
 
-	kmem_free(source, MAXNAMELEN + strlen(MOS_DIR_NAME) + 1);
+	kmem_free(source, ZFS_MAX_DATASET_NAME_LEN);
 	kmem_free(baseza, sizeof (zap_attribute_t));
 	kmem_free(basezc, sizeof (zap_cursor_t));
 	kmem_free(za, sizeof (zap_attribute_t));
diff --git a/module/zfs/dsl_dir.c b/module/zfs/dsl_dir.c
index 8983e0793..ae67b362e 100644
--- a/module/zfs/dsl_dir.c
+++ b/module/zfs/dsl_dir.c
@@ -299,13 +299,14 @@ dsl_dir_async_rele(dsl_dir_t *dd, void *tag)
 	dmu_buf_rele(dd->dd_dbuf, tag);
 }
 
-/* buf must be long enough (MAXNAMELEN + strlen(MOS_DIR_NAME) + 1 should do) */
+/* buf must be at least ZFS_MAX_DATASET_NAME_LEN bytes */
 void
 dsl_dir_name(dsl_dir_t *dd, char *buf)
 {
 	if (dd->dd_parent) {
 		dsl_dir_name(dd->dd_parent, buf);
-		(void) strcat(buf, "/");
+		VERIFY3U(strlcat(buf, "/", ZFS_MAX_DATASET_NAME_LEN), <,
+		    ZFS_MAX_DATASET_NAME_LEN);
 	} else {
 		buf[0] = '\0';
 	}
@@ -315,10 +316,12 @@ dsl_dir_name(dsl_dir_t *dd, char *buf)
 		 * dprintf_dd() with dd_lock held
 		 */
 		mutex_enter(&dd->dd_lock);
-		(void) strcat(buf, dd->dd_myname);
+		VERIFY3U(strlcat(buf, dd->dd_myname, ZFS_MAX_DATASET_NAME_LEN),
+		    <, ZFS_MAX_DATASET_NAME_LEN);
 		mutex_exit(&dd->dd_lock);
 	} else {
-		(void) strcat(buf, dd->dd_myname);
+		VERIFY3U(strlcat(buf, dd->dd_myname, ZFS_MAX_DATASET_NAME_LEN),
+		    <, ZFS_MAX_DATASET_NAME_LEN);
 	}
 }
 
@@ -367,12 +370,12 @@ getcomponent(const char *path, char *component, const char **nextp)
 		if (p != NULL &&
 		    (p[0] != '@' || strpbrk(path+1, "/@") || p[1] == '\0'))
 			return (SET_ERROR(EINVAL));
-		if (strlen(path) >= MAXNAMELEN)
+		if (strlen(path) >= ZFS_MAX_DATASET_NAME_LEN)
 			return (SET_ERROR(ENAMETOOLONG));
 		(void) strcpy(component, path);
 		p = NULL;
 	} else if (p[0] == '/') {
-		if (p - path >= MAXNAMELEN)
+		if (p - path >= ZFS_MAX_DATASET_NAME_LEN)
 			return (SET_ERROR(ENAMETOOLONG));
 		(void) strncpy(component, path, p - path);
 		component[p - path] = '\0';
@@ -384,7 +387,7 @@ getcomponent(const char *path, char *component, const char **nextp)
 		 */
 		if (strchr(path, '/'))
 			return (SET_ERROR(EINVAL));
-		if (p - path >= MAXNAMELEN)
+		if (p - path >= ZFS_MAX_DATASET_NAME_LEN)
 			return (SET_ERROR(ENAMETOOLONG));
 		(void) strncpy(component, path, p - path);
 		component[p - path] = '\0';
@@ -412,7 +415,7 @@ dsl_dir_hold(dsl_pool_t *dp, const char *name, void *tag,
 	dsl_dir_t *dd;
 	uint64_t ddobj;
 
-	buf = kmem_alloc(MAXNAMELEN, KM_SLEEP);
+	buf = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 	err = getcomponent(name, buf, &next);
 	if (err != 0)
 		goto error;
@@ -479,7 +482,7 @@ dsl_dir_hold(dsl_pool_t *dp, const char *name, void *tag,
 		*tailp = next;
 	*ddp = dd;
 error:
-	kmem_free(buf, MAXNAMELEN);
+	kmem_free(buf, ZFS_MAX_DATASET_NAME_LEN);
 	return (err);
 }
 
@@ -974,7 +977,7 @@ dsl_dir_stats(dsl_dir_t *dd, nvlist_t *nv)
 
 	if (dsl_dir_is_clone(dd)) {
 		dsl_dataset_t *ds;
-		char buf[MAXNAMELEN];
+		char buf[ZFS_MAX_DATASET_NAME_LEN];
 
 		VERIFY0(dsl_dataset_hold_obj(dd->dd_pool,
 		    dsl_dir_phys(dd)->dd_origin_obj, FTAG, &ds));
@@ -1691,11 +1694,11 @@ static int
 dsl_valid_rename(dsl_pool_t *dp, dsl_dataset_t *ds, void *arg)
 {
 	int *deltap = arg;
-	char namebuf[MAXNAMELEN];
+	char namebuf[ZFS_MAX_DATASET_NAME_LEN];
 
 	dsl_dataset_name(ds, namebuf);
 
-	if (strlen(namebuf) + *deltap >= MAXNAMELEN)
+	if (strlen(namebuf) + *deltap >= ZFS_MAX_DATASET_NAME_LEN)
 		return (SET_ERROR(ENAMETOOLONG));
 	return (0);
 }
diff --git a/module/zfs/dsl_prop.c b/module/zfs/dsl_prop.c
index 361473275..66e899a57 100644
--- a/module/zfs/dsl_prop.c
+++ b/module/zfs/dsl_prop.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2013 Martin Matuska. All rights reserved.
  * Copyright 2015, Joyent, Inc.
  */
@@ -1095,7 +1095,7 @@ dsl_prop_get_all_ds(dsl_dataset_t *ds, nvlist_t **nvp,
 	dsl_pool_t *dp = dd->dd_pool;
 	objset_t *mos = dp->dp_meta_objset;
 	int err = 0;
-	char setpoint[MAXNAMELEN];
+	char setpoint[ZFS_MAX_DATASET_NAME_LEN];
 
 	VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
 
diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c
index 72163521e..6c5f1f0b5 100644
--- a/module/zfs/dsl_scan.c
+++ b/module/zfs/dsl_scan.c
@@ -1115,7 +1115,7 @@ dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx)
 		 * rootbp's birth time is < cur_min_txg.  Then we will
 		 * add the next snapshots/clones to the work queue.
 		 */
-		char *dsname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
+		char *dsname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 		dsl_dataset_name(ds, dsname);
 		zfs_dbgmsg("scanning dataset %llu (%s) is unnecessary because "
 		    "cur_min_txg (%llu) >= max_txg (%llu)",
@@ -1146,7 +1146,7 @@ dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx)
 	dmu_buf_will_dirty(ds->ds_dbuf, tx);
 	dsl_scan_visit_rootbp(scn, ds, &dsl_dataset_phys(ds)->ds_bp, tx);
 
-	dsname = kmem_alloc(ZFS_MAXNAMELEN, KM_SLEEP);
+	dsname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 	dsl_dataset_name(ds, dsname);
 	zfs_dbgmsg("scanned dataset %llu (%s) with min=%llu max=%llu; "
 	    "pausing=%u",
@@ -1154,7 +1154,7 @@ dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx)
 	    (longlong_t)scn->scn_phys.scn_cur_min_txg,
 	    (longlong_t)scn->scn_phys.scn_cur_max_txg,
 	    (int)scn->scn_pausing);
-	kmem_free(dsname, ZFS_MAXNAMELEN);
+	kmem_free(dsname, ZFS_MAX_DATASET_NAME_LEN);
 
 	if (scn->scn_pausing)
 		goto out;
diff --git a/module/zfs/dsl_userhold.c b/module/zfs/dsl_userhold.c
index 1b234ed48..a6d1aa937 100644
--- a/module/zfs/dsl_userhold.c
+++ b/module/zfs/dsl_userhold.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  */
 
@@ -181,7 +181,7 @@ dsl_dataset_user_hold_sync_one_impl(nvlist_t *tmpholds, dsl_dataset_t *ds,
 }
 
 typedef struct zfs_hold_cleanup_arg {
-	char zhca_spaname[MAXNAMELEN];
+	char zhca_spaname[ZFS_MAX_DATASET_NAME_LEN];
 	uint64_t zhca_spa_load_guid;
 	nvlist_t *zhca_holds;
 } zfs_hold_cleanup_arg_t;
@@ -580,7 +580,7 @@ dsl_dataset_user_release_impl(nvlist_t *holds, nvlist_t *errlist,
 			error = dsl_dataset_hold_obj_string(tmpdp,
 			    nvpair_name(pair), FTAG, &ds);
 			if (error == 0) {
-				char name[MAXNAMELEN];
+				char name[ZFS_MAX_DATASET_NAME_LEN];
 				dsl_dataset_name(ds, name);
 				dsl_pool_config_exit(tmpdp, FTAG);
 				dsl_dataset_rele(ds, FTAG);
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index d1aefe585..9570204f4 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -361,8 +361,7 @@ spa_prop_get(spa_t *spa, nvlist_t **nvp)
 					break;
 				}
 
-				strval = kmem_alloc(
-				    MAXNAMELEN + strlen(MOS_DIR_NAME) + 1,
+				strval = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN,
 				    KM_SLEEP);
 				dsl_dataset_name(ds, strval);
 				dsl_dataset_rele(ds, FTAG);
@@ -375,8 +374,7 @@ spa_prop_get(spa_t *spa, nvlist_t **nvp)
 			spa_prop_add_list(*nvp, prop, strval, intval, src);
 
 			if (strval != NULL)
-				kmem_free(strval,
-				    MAXNAMELEN + strlen(MOS_DIR_NAME) + 1);
+				kmem_free(strval, ZFS_MAX_DATASET_NAME_LEN);
 
 			break;
 
diff --git a/module/zfs/spa_history.c b/module/zfs/spa_history.c
index 01aa4641e..cf6fc224a 100644
--- a/module/zfs/spa_history.c
+++ b/module/zfs/spa_history.c
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
  */
 
 #include <sys/spa.h>
@@ -493,7 +493,7 @@ spa_history_log_internal_ds(dsl_dataset_t *ds, const char *operation,
     dmu_tx_t *tx, const char *fmt, ...)
 {
 	va_list adx;
-	char namebuf[MAXNAMELEN];
+	char namebuf[ZFS_MAX_DATASET_NAME_LEN];
 	nvlist_t *nvl = fnvlist_alloc();
 
 	ASSERT(tx != NULL);
@@ -512,7 +512,7 @@ spa_history_log_internal_dd(dsl_dir_t *dd, const char *operation,
     dmu_tx_t *tx, const char *fmt, ...)
 {
 	va_list adx;
-	char namebuf[MAXNAMELEN];
+	char namebuf[ZFS_MAX_DATASET_NAME_LEN];
 	nvlist_t *nvl = fnvlist_alloc();
 
 	ASSERT(tx != NULL);
diff --git a/module/zfs/zfs_ctldir.c b/module/zfs/zfs_ctldir.c
index e47cfc878..d279d1828 100644
--- a/module/zfs/zfs_ctldir.c
+++ b/module/zfs/zfs_ctldir.c
@@ -749,12 +749,13 @@ zfsctl_snapshot_path_objset(zfs_sb_t *zsb, uint64_t objsetid,
 		return (ENOENT);
 
 	cookie = spl_fstrans_mark();
-	snapname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
+	snapname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 
 	while (error == 0) {
 		dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
-		error = dmu_snapshot_list_next(zsb->z_os, MAXNAMELEN,
-		    snapname, &id, &pos, &case_conflict);
+		error = dmu_snapshot_list_next(zsb->z_os,
+		    ZFS_MAX_DATASET_NAME_LEN, snapname, &id, &pos,
+		    &case_conflict);
 		dsl_pool_config_exit(dmu_objset_pool(os), FTAG);
 		if (error)
 			goto out;
@@ -767,7 +768,7 @@ zfsctl_snapshot_path_objset(zfs_sb_t *zsb, uint64_t objsetid,
 	snprintf(full_path, path_len - 1, "%s/.zfs/snapshot/%s",
 	    zsb->z_mntopts->z_mntpoint, snapname);
 out:
-	kmem_free(snapname, MAXNAMELEN);
+	kmem_free(snapname, ZFS_MAX_DATASET_NAME_LEN);
 	spl_fstrans_unmark(cookie);
 
 	return (error);
@@ -854,14 +855,14 @@ zfsctl_snapdir_rename(struct inode *sdip, char *snm,
 
 	ZFS_ENTER(zsb);
 
-	to = kmem_alloc(MAXNAMELEN, KM_SLEEP);
-	from = kmem_alloc(MAXNAMELEN, KM_SLEEP);
-	real = kmem_alloc(MAXNAMELEN, KM_SLEEP);
-	fsname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
+	to = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
+	from = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
+	real = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
+	fsname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 
 	if (zsb->z_case == ZFS_CASE_INSENSITIVE) {
 		error = dmu_snapshot_realname(zsb->z_os, snm, real,
-		    MAXNAMELEN, NULL);
+		    ZFS_MAX_DATASET_NAME_LEN, NULL);
 		if (error == 0) {
 			snm = real;
 		} else if (error != ENOTSUP) {
@@ -871,9 +872,11 @@ zfsctl_snapdir_rename(struct inode *sdip, char *snm,
 
 	dmu_objset_name(zsb->z_os, fsname);
 
-	error = zfsctl_snapshot_name(ITOZSB(sdip), snm, MAXNAMELEN, from);
+	error = zfsctl_snapshot_name(ITOZSB(sdip), snm,
+	    ZFS_MAX_DATASET_NAME_LEN, from);
 	if (error == 0)
-		error = zfsctl_snapshot_name(ITOZSB(tdip), tnm, MAXNAMELEN, to);
+		error = zfsctl_snapshot_name(ITOZSB(tdip), tnm,
+	    ZFS_MAX_DATASET_NAME_LEN, to);
 	if (error == 0)
 		error = zfs_secpolicy_rename_perms(from, to, cr);
 	if (error != 0)
@@ -903,10 +906,10 @@ zfsctl_snapdir_rename(struct inode *sdip, char *snm,
 
 	rw_exit(&zfs_snapshot_lock);
 out:
-	kmem_free(from, MAXNAMELEN);
-	kmem_free(to, MAXNAMELEN);
-	kmem_free(real, MAXNAMELEN);
-	kmem_free(fsname, MAXNAMELEN);
+	kmem_free(from, ZFS_MAX_DATASET_NAME_LEN);
+	kmem_free(to, ZFS_MAX_DATASET_NAME_LEN);
+	kmem_free(real, ZFS_MAX_DATASET_NAME_LEN);
+	kmem_free(fsname, ZFS_MAX_DATASET_NAME_LEN);
 
 	ZFS_EXIT(zsb);
 
@@ -929,12 +932,12 @@ zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr, int flags)
 
 	ZFS_ENTER(zsb);
 
-	snapname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
-	real = kmem_alloc(MAXNAMELEN, KM_SLEEP);
+	snapname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
+	real = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 
 	if (zsb->z_case == ZFS_CASE_INSENSITIVE) {
 		error = dmu_snapshot_realname(zsb->z_os, name, real,
-		    MAXNAMELEN, NULL);
+		    ZFS_MAX_DATASET_NAME_LEN, NULL);
 		if (error == 0) {
 			name = real;
 		} else if (error != ENOTSUP) {
@@ -942,7 +945,8 @@ zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr, int flags)
 		}
 	}
 
-	error = zfsctl_snapshot_name(ITOZSB(dip), name, MAXNAMELEN, snapname);
+	error = zfsctl_snapshot_name(ITOZSB(dip), name,
+	    ZFS_MAX_DATASET_NAME_LEN, snapname);
 	if (error == 0)
 		error = zfs_secpolicy_destroy_perms(snapname, cr);
 	if (error != 0)
@@ -952,8 +956,8 @@ zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr, int flags)
 	if ((error == 0) || (error == ENOENT))
 		error = dsl_destroy_snapshot(snapname, B_FALSE);
 out:
-	kmem_free(snapname, MAXNAMELEN);
-	kmem_free(real, MAXNAMELEN);
+	kmem_free(snapname, ZFS_MAX_DATASET_NAME_LEN);
+	kmem_free(real, ZFS_MAX_DATASET_NAME_LEN);
 
 	ZFS_EXIT(zsb);
 
@@ -975,7 +979,7 @@ zfsctl_snapdir_mkdir(struct inode *dip, char *dirname, vattr_t *vap,
 	if (!zfs_admin_snapshot)
 		return (EACCES);
 
-	dsname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
+	dsname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 
 	if (zfs_component_namecheck(dirname, NULL, NULL) != 0) {
 		error = SET_ERROR(EILSEQ);
@@ -997,7 +1001,7 @@ zfsctl_snapdir_mkdir(struct inode *dip, char *dirname, vattr_t *vap,
 		    0, cr, NULL, NULL);
 	}
 out:
-	kmem_free(dsname, MAXNAMELEN);
+	kmem_free(dsname, ZFS_MAX_DATASET_NAME_LEN);
 
 	return (error);
 }
@@ -1075,11 +1079,11 @@ zfsctl_snapshot_mount(struct path *path, int flags)
 	zsb = ITOZSB(ip);
 	ZFS_ENTER(zsb);
 
-	full_name = kmem_zalloc(MAXNAMELEN, KM_SLEEP);
+	full_name = kmem_zalloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 	full_path = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
 
 	error = zfsctl_snapshot_name(zsb, dname(dentry),
-	    MAXNAMELEN, full_name);
+	    ZFS_MAX_DATASET_NAME_LEN, full_name);
 	if (error)
 		goto error;
 
@@ -1153,7 +1157,7 @@ zfsctl_snapshot_mount(struct path *path, int flags)
 	}
 	path_put(&spath);
 error:
-	kmem_free(full_name, MAXNAMELEN);
+	kmem_free(full_name, ZFS_MAX_DATASET_NAME_LEN);
 	kmem_free(full_path, MAXPATHLEN);
 
 	ZFS_EXIT(zsb);
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index 96f282201..09f83a5cf 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -604,7 +604,7 @@ zfs_secpolicy_setprop(const char *dsname, zfs_prop_t prop, nvpair_t *propval,
 	case ZFS_PROP_SNAPSHOT_LIMIT:
 		if (!INGLOBALZONE(curproc)) {
 			uint64_t zoned;
-			char setpoint[MAXNAMELEN];
+			char setpoint[ZFS_MAX_DATASET_NAME_LEN];
 			/*
 			 * Unprivileged users are allowed to modify the
 			 * limit on things *under* (ie. contained by)
@@ -846,7 +846,7 @@ zfs_secpolicy_destroy_snaps(zfs_cmd_t *zc, nvlist_t *innvl, cred_t *cr)
 int
 zfs_secpolicy_rename_perms(const char *from, const char *to, cred_t *cr)
 {
-	char	parentname[MAXNAMELEN];
+	char	parentname[ZFS_MAX_DATASET_NAME_LEN];
 	int	error;
 
 	if ((error = zfs_secpolicy_write_perms(from,
@@ -899,7 +899,7 @@ zfs_secpolicy_promote(zfs_cmd_t *zc, nvlist_t *innvl, cred_t *cr)
 	error = dsl_dataset_hold(dp, zc->zc_name, FTAG, &clone);
 
 	if (error == 0) {
-		char parentname[MAXNAMELEN];
+		char parentname[ZFS_MAX_DATASET_NAME_LEN];
 		dsl_dataset_t *origin = NULL;
 		dsl_dir_t *dd;
 		dd = clone->ds_dir;
@@ -1076,7 +1076,7 @@ zfs_secpolicy_log_history(zfs_cmd_t *zc, nvlist_t *innvl, cred_t *cr)
 static int
 zfs_secpolicy_create_clone(zfs_cmd_t *zc, nvlist_t *innvl, cred_t *cr)
 {
-	char	parentname[MAXNAMELEN];
+	char	parentname[ZFS_MAX_DATASET_NAME_LEN];
 	int	error;
 	char	*origin;
 
@@ -1219,7 +1219,7 @@ zfs_secpolicy_hold(zfs_cmd_t *zc, nvlist_t *innvl, cred_t *cr)
 
 	for (pair = nvlist_next_nvpair(holds, NULL); pair != NULL;
 	    pair = nvlist_next_nvpair(holds, pair)) {
-		char fsname[MAXNAMELEN];
+		char fsname[ZFS_MAX_DATASET_NAME_LEN];
 		error = dmu_fsname(nvpair_name(pair), fsname);
 		if (error != 0)
 			return (error);
@@ -1240,7 +1240,7 @@ zfs_secpolicy_release(zfs_cmd_t *zc, nvlist_t *innvl, cred_t *cr)
 
 	for (pair = nvlist_next_nvpair(innvl, NULL); pair != NULL;
 	    pair = nvlist_next_nvpair(innvl, pair)) {
-		char fsname[MAXNAMELEN];
+		char fsname[ZFS_MAX_DATASET_NAME_LEN];
 		error = dmu_fsname(nvpair_name(pair), fsname);
 		if (error != 0)
 			return (error);
@@ -2260,7 +2260,8 @@ zfs_ioc_snapshot_list_next(zfs_cmd_t *zc)
 	 * A dataset name of maximum length cannot have any snapshots,
 	 * so exit immediately.
 	 */
-	if (strlcat(zc->zc_name, "@", sizeof (zc->zc_name)) >= MAXNAMELEN) {
+	if (strlcat(zc->zc_name, "@", sizeof (zc->zc_name)) >=
+	    ZFS_MAX_DATASET_NAME_LEN) {
 		dmu_objset_rele(os, FTAG);
 		return (SET_ERROR(ESRCH));
 	}
@@ -3048,7 +3049,7 @@ zfs_fill_zplprops(const char *dataset, nvlist_t *createprops,
 	boolean_t fuids_ok, sa_ok;
 	uint64_t zplver = ZPL_VERSION;
 	objset_t *os = NULL;
-	char parentname[MAXNAMELEN];
+	char parentname[ZFS_MAX_DATASET_NAME_LEN];
 	char *cp;
 	spa_t *spa;
 	uint64_t spa_vers;
@@ -3414,7 +3415,7 @@ zfs_destroy_unmount_origin(const char *fsname)
 		return;
 	ds = dmu_objset_ds(os);
 	if (dsl_dir_is_clone(ds->ds_dir) && DS_IS_DEFER_DESTROY(ds->ds_prev)) {
-		char originname[MAXNAMELEN];
+		char originname[ZFS_MAX_DATASET_NAME_LEN];
 		dsl_dataset_name(ds->ds_prev, originname);
 		dmu_objset_rele(os, FTAG);
 		(void) zfs_unmount_snap(originname);
@@ -4266,7 +4267,7 @@ zfs_ioc_recv(zfs_cmd_t *zc)
 	nvlist_t *props = NULL;
 	char *origin = NULL;
 	char *tosnap;
-	char tofs[ZFS_MAXNAMELEN];
+	char tofs[ZFS_MAX_DATASET_NAME_LEN];
 	int error = 0;
 
 	if (dataset_namecheck(zc->zc_value, NULL, NULL) != 0 ||
@@ -4344,7 +4345,7 @@ zfs_ioc_recv_new(const char *fsname, nvlist_t *innvl, nvlist_t *outnvl)
 	char *snapname = NULL;
 	char *origin = NULL;
 	char *tosnap;
-	char tofs[ZFS_MAXNAMELEN];
+	char tofs[ZFS_MAX_DATASET_NAME_LEN];
 	boolean_t force;
 	boolean_t resumable;
 	uint64_t action_handle = 0;
diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index a72841c15..ef04b203d 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -1020,7 +1020,7 @@ zfs_statvfs(struct dentry *dentry, struct kstatfs *statp)
 	statp->f_fsid.val[0] = (uint32_t)fsid;
 	statp->f_fsid.val[1] = (uint32_t)(fsid >> 32);
 	statp->f_type = ZFS_SUPER_MAGIC;
-	statp->f_namelen = ZFS_MAXNAMELEN;
+	statp->f_namelen = MAXNAMELEN - 1;
 
 	/*
 	 * We have all of 40 characters to stuff a string here.
diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index 988ffec29..863ccb930 100644
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -2080,7 +2080,7 @@ typedef struct zil_replay_arg {
 static int
 zil_replay_error(zilog_t *zilog, lr_t *lr, int error)
 {
-	char name[MAXNAMELEN];
+	char name[ZFS_MAX_DATASET_NAME_LEN];
 
 	zilog->zl_replaying_seq--;	/* didn't actually replay this one */
 
diff --git a/module/zfs/zpl_inode.c b/module/zfs/zpl_inode.c
index 089e3a1bc..8c75698e5 100644
--- a/module/zfs/zpl_inode.c
+++ b/module/zfs/zpl_inode.c
@@ -50,7 +50,7 @@ zpl_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 	int zfs_flags = 0;
 	zfs_sb_t *zsb = dentry->d_sb->s_fs_info;
 
-	if (dlen(dentry) > ZFS_MAXNAMELEN)
+	if (dlen(dentry) > ZFS_MAX_DATASET_NAME_LEN)
 		return (ERR_PTR(-ENAMETOOLONG));
 
 	crhold(cr);