Add zfs module feature and property info to sysfs

This extends our sysfs '/sys/module/zfs' entry to include feature 
and property attributes. The primary consumer of this information 
is user processes, like the zfs CLI, that need to know what the 
current loaded ZFS module supports. The libzfs binary will consult 
this information when instantiating the zfs and zpool property 
tables and the pool features table.

This introduces 4 kernel objects (dirs) into '/sys/module/zfs'
with corresponding attributes (files):
  features.runtime
  features.pool
  properties.dataset
  properties.pool

Reviewed-by: Matthew Ahrens <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Don Brady <[email protected]>
Closes #7706 

6 files changed, 707 insertions, 1 deletions

diff --git a/module/zcommon/zfeature_common.c b/module/zcommon/zfeature_common.c
index f5c98933c..e2b0fd511 100644
--- a/module/zcommon/zfeature_common.c
+++ b/module/zcommon/zfeature_common.c
@@ -29,11 +29,13 @@
 #ifndef _KERNEL
 #include <errno.h>
 #include <string.h>
+#include <sys/stat.h>
 #endif
 #include <sys/debug.h>
 #include <sys/fs/zfs.h>
 #include <sys/inttypes.h>
 #include <sys/types.h>
+#include <sys/zfs_sysfs.h>
 #include "zfeature_common.h"
 
 /*
@@ -101,10 +103,29 @@ zfeature_is_supported(const char *guid)
 }
 
 int
+zfeature_lookup_guid(const char *guid, spa_feature_t *res)
+{
+	for (spa_feature_t i = 0; i < SPA_FEATURES; i++) {
+		zfeature_info_t *feature = &spa_feature_table[i];
+		if (!feature->fi_zfs_mod_supported)
+			continue;
+		if (strcmp(guid, feature->fi_guid) == 0) {
+			if (res != NULL)
+				*res = i;
+			return (0);
+		}
+	}
+
+	return (ENOENT);
+}
+
+int
 zfeature_lookup_name(const char *name, spa_feature_t *res)
 {
 	for (spa_feature_t i = 0; i < SPA_FEATURES; i++) {
 		zfeature_info_t *feature = &spa_feature_table[i];
+		if (!feature->fi_zfs_mod_supported)
+			continue;
 		if (strcmp(name, feature->fi_uname) == 0) {
 			if (res != NULL)
 				*res = i;
@@ -137,6 +158,34 @@ deps_contains_feature(const spa_feature_t *deps, const spa_feature_t feature)
 	return (B_FALSE);
 }
 
+static boolean_t
+zfs_mod_supported_feature(const char *name)
+{
+	/*
+	 * The zfs module spa_feature_table[], whether in-kernel or in
+	 * libzpool, always supports all the features. libzfs needs to
+	 * query the running module, via sysfs, to determine which
+	 * features are supported.
+	 */
+#if defined(_KERNEL) || defined(LIB_ZPOOL_BUILD)
+	return (B_TRUE);
+#else
+	struct stat64 statbuf;
+	char *path;
+	boolean_t supported = B_FALSE;
+	int len;
+
+	len = asprintf(&path, "%s/%s/%s", ZFS_SYSFS_DIR,
+	    ZFS_SYSFS_POOL_FEATURES, name);
+
+	if (len > 0) {
+		supported = !!(stat64(path, &statbuf) == 0);
+		free(path);
+	}
+	return (supported);
+#endif
+}
+
 static void
 zfeature_register(spa_feature_t fid, const char *guid, const char *name,
     const char *desc, zfeature_flags_t flags, const spa_feature_t *deps)
@@ -163,6 +212,7 @@ zfeature_register(spa_feature_t fid, const char *guid, const char *name,
 	feature->fi_desc = desc;
 	feature->fi_flags = flags;
 	feature->fi_depends = deps;
+	feature->fi_zfs_mod_supported = zfs_mod_supported_feature(guid);
 }
 
 void
@@ -361,6 +411,7 @@ zpool_feature_init(void)
 }
 
 #if defined(_KERNEL)
+EXPORT_SYMBOL(zfeature_lookup_guid);
 EXPORT_SYMBOL(zfeature_lookup_name);
 EXPORT_SYMBOL(zfeature_is_supported);
 EXPORT_SYMBOL(zfeature_is_valid_guid);
diff --git a/module/zcommon/zfs_prop.c b/module/zcommon/zfs_prop.c
index 28eb1255b..04bb33e5e 100644
--- a/module/zcommon/zfs_prop.c
+++ b/module/zcommon/zfs_prop.c
@@ -720,7 +720,8 @@ zfs_prop_readonly(zfs_prop_t prop)
 boolean_t
 zfs_prop_visible(zfs_prop_t prop)
 {
-	return (zfs_prop_table[prop].pd_visible);
+	return (zfs_prop_table[prop].pd_visible &&
+	    zfs_prop_table[prop].pd_zfs_mod_supported);
 }
 
 /*
diff --git a/module/zcommon/zprop_common.c b/module/zcommon/zprop_common.c
index 838988a4c..0ce2ee762 100644
--- a/module/zcommon/zprop_common.c
+++ b/module/zcommon/zprop_common.c
@@ -34,6 +34,7 @@
 #include <sys/spa.h>
 #include <sys/zfs_acl.h>
 #include <sys/zfs_ioctl.h>
+#include <sys/zfs_sysfs.h>
 #include <sys/zfs_znode.h>
 #include <sys/fs/zfs.h>
 
@@ -48,6 +49,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
+#include <sys/stat.h>
 #endif
 
 static zprop_desc_t *
@@ -68,6 +70,34 @@ zprop_get_numprops(zfs_type_t type)
 		return (ZFS_NUM_PROPS);
 }
 
+static boolean_t
+zfs_mod_supported_prop(const char *name, zfs_type_t type)
+{
+/*
+ * The zfs module spa_feature_table[], whether in-kernel or in libzpool,
+ * always supports all the properties. libzfs needs to query the running
+ * module, via sysfs, to determine which properties are supported.
+ */
+#if defined(_KERNEL) || defined(LIB_ZPOOL_BUILD)
+	return (B_TRUE);
+#else
+	struct stat64 statbuf;
+	char *path;
+	boolean_t supported = B_FALSE;
+	int len;
+
+	len = asprintf(&path, "%s/%s/%s", ZFS_SYSFS_DIR,
+	    (type == ZFS_TYPE_POOL) ? ZFS_SYSFS_POOL_PROPERTIES :
+	    ZFS_SYSFS_DATASET_PROPERTIES, name);
+
+	if (len > 0) {
+		supported = !!(stat64(path, &statbuf) == 0);
+		free(path);
+	}
+	return (supported);
+#endif
+}
+
 void
 zprop_register_impl(int prop, const char *name, zprop_type_t type,
     uint64_t numdefault, const char *strdefault, zprop_attr_t attr,
@@ -94,6 +124,7 @@ zprop_register_impl(int prop, const char *name, zprop_type_t type,
 	pd->pd_colname = colname;
 	pd->pd_rightalign = rightalign;
 	pd->pd_visible = visible;
+	pd->pd_zfs_mod_supported = zfs_mod_supported_prop(name, objset_types);
 	pd->pd_table = idx_tbl;
 	pd->pd_table_size = 0;
 	while (idx_tbl && (idx_tbl++)->pi_name != NULL)
@@ -193,6 +224,7 @@ zprop_iter_common(zprop_func func, void *cb, boolean_t show_all,
 	prop = ZPROP_CONT;
 	for (i = 0; i < num_props; i++) {
 		if ((order[i]->pd_visible || show_all) &&
+		    order[i]->pd_zfs_mod_supported &&
 		    (func(order[i]->pd_propnum, cb) != ZPROP_CONT)) {
 			prop = order[i]->pd_propnum;
 			break;
diff --git a/module/zfs/Makefile.in b/module/zfs/Makefile.in
index 2c27cf65c..6fd24757c 100644
--- a/module/zfs/Makefile.in
+++ b/module/zfs/Makefile.in
@@ -120,6 +120,7 @@ $(MODULE)-objs += zfs_ratelimit.o
 $(MODULE)-objs += zfs_replay.o
 $(MODULE)-objs += zfs_rlock.o
 $(MODULE)-objs += zfs_sa.o
+$(MODULE)-objs += zfs_sysfs.o
 $(MODULE)-objs += zfs_vfsops.o
 $(MODULE)-objs += zfs_vnops.o
 $(MODULE)-objs += zfs_znode.o
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index 6a5846bfe..4ea9fa41a 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -187,6 +187,7 @@
 #include <sys/zcp.h>
 #include <sys/zio_checksum.h>
 #include <sys/vdev_removal.h>
+#include <sys/zfs_sysfs.h>
 
 #include <linux/miscdevice.h>
 #include <linux/slab.h>
@@ -7083,6 +7084,7 @@ _init(void)
 	zfs_init();
 
 	zfs_ioctl_init();
+	zfs_sysfs_init();
 
 	if ((error = zfs_attach()) != 0)
 		goto out;
@@ -7102,6 +7104,7 @@ _init(void)
 	return (0);
 
 out:
+	zfs_sysfs_fini();
 	zfs_fini();
 	spa_fini();
 	(void) zvol_fini();
@@ -7116,6 +7119,7 @@ static void __exit
 _fini(void)
 {
 	zfs_detach();
+	zfs_sysfs_fini();
 	zfs_fini();
 	spa_fini();
 	zvol_fini();
diff --git a/module/zfs/zfs_sysfs.c b/module/zfs/zfs_sysfs.c
new file mode 100644
index 000000000..6bf2e23aa
--- /dev/null
+++ b/module/zfs/zfs_sysfs.c
@@ -0,0 +1,617 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2018 by Delphix. All rights reserved.
+ */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/zfeature.h>
+#include <sys/zfs_ioctl.h>
+#include <sys/zfs_sysfs.h>
+#include <sys/kmem.h>
+#include <sys/fs/zfs.h>
+#include <linux/kobject.h>
+
+#include "zfs_prop.h"
+
+#if !defined(_KERNEL)
+#error kernel builds only
+#endif
+
+/*
+ * ZFS Module sysfs support
+ *
+ * This extends our sysfs '/sys/module/zfs' entry to include feature
+ * and property attributes. The primary consumer of this information
+ * is user processes, like the zfs CLI, that need to know what the
+ * current loaded ZFS module supports. The libzfs binary will consult
+ * this information when instantiating the zfs|zpool property tables
+ * and the pool features table.
+ *
+ * The added top-level directories are:
+ * /sys/module/zfs
+ *		├── features.kernel
+ *		├── features.pool
+ *		├── properties.dataset
+ *		└── properties.pool
+ *
+ * The local interface for the zfs kobjects includes:
+ *	zfs_kobj_init()
+ *	zfs_kobj_add()
+ *	zfs_kobj_release()
+ *	zfs_kobj_add_attr()
+ *	zfs_kobj_fini()
+ */
+
+/*
+ * A zfs_mod_kobj_t represents a zfs kobject under '/sys/module/zfs'
+ */
+struct zfs_mod_kobj;
+typedef struct zfs_mod_kobj zfs_mod_kobj_t;
+
+struct zfs_mod_kobj {
+	struct kobject		zko_kobj;
+	struct kobj_type	zko_kobj_type;
+	struct sysfs_ops	zko_sysfs_ops;
+	size_t			zko_attr_count;
+	struct attribute	*zko_attr_list;		/* allocated */
+	struct attribute	**zko_default_attrs;	/* allocated */
+	size_t			zko_child_count;
+	zfs_mod_kobj_t		*zko_children;		/* allocated */
+};
+
+#define	ATTR_TABLE_SIZE(cnt)	(sizeof (struct attribute) * (cnt))
+/* Note +1 for NULL terminator slot */
+#define	DEFAULT_ATTR_SIZE(cnt)	(sizeof (struct attribute *) * (cnt + 1))
+#define	CHILD_TABLE_SIZE(cnt)	(sizeof (zfs_mod_kobj_t) * (cnt))
+
+/*
+ * These are the top-level kobjects under '/sys/module/zfs/'
+ */
+static zfs_mod_kobj_t kernel_features_kobj;
+static zfs_mod_kobj_t pool_features_kobj;
+static zfs_mod_kobj_t dataset_props_kobj;
+static zfs_mod_kobj_t pool_props_kobj;
+
+/*
+ * The show function is used to provide the content
+ * of an attribute into a PAGE_SIZE buffer.
+ */
+typedef ssize_t	(*sysfs_show_func)(struct kobject *, struct attribute *,
+    char *);
+
+static void
+zfs_kobj_fini(zfs_mod_kobj_t *zkobj)
+{
+	/* finialize any child kobjects */
+	if (zkobj->zko_child_count != 0) {
+		ASSERT(zkobj->zko_children);
+		for (int i = 0; i < zkobj->zko_child_count; i++)
+			zfs_kobj_fini(&zkobj->zko_children[i]);
+	}
+
+	/* kobject_put() will call zfs_kobj_release() to release memory */
+	kobject_del(&zkobj->zko_kobj);
+	kobject_put(&zkobj->zko_kobj);
+}
+
+static void
+zfs_kobj_release(struct kobject *kobj)
+{
+	zfs_mod_kobj_t *zkobj = container_of(kobj, zfs_mod_kobj_t, zko_kobj);
+
+	if (zkobj->zko_attr_count != 0) {
+		ASSERT(zkobj->zko_attr_list);
+		ASSERT(zkobj->zko_default_attrs);
+
+		kmem_free(zkobj->zko_attr_list,
+		    ATTR_TABLE_SIZE(zkobj->zko_attr_count));
+		kmem_free(zkobj->zko_default_attrs,
+		    DEFAULT_ATTR_SIZE(zkobj->zko_attr_count));
+		zkobj->zko_attr_count = 0;
+		zkobj->zko_attr_list = NULL;
+		zkobj->zko_default_attrs = NULL;
+	}
+	if (zkobj->zko_child_count != 0) {
+		ASSERT(zkobj->zko_children);
+
+		kmem_free(zkobj->zko_children,
+		    CHILD_TABLE_SIZE(zkobj->zko_child_count));
+		zkobj->zko_child_count = 0;
+		zkobj->zko_children = NULL;
+	}
+}
+
+static void
+zfs_kobj_add_attr(zfs_mod_kobj_t *zkobj, int attr_num, const char *attr_name)
+{
+	VERIFY3U(attr_num, <, zkobj->zko_attr_count);
+	ASSERT(zkobj->zko_attr_list);
+	ASSERT(zkobj->zko_default_attrs);
+
+	zkobj->zko_attr_list[attr_num].name = attr_name;
+	zkobj->zko_attr_list[attr_num].mode = 0444;
+	zkobj->zko_default_attrs[attr_num] = &zkobj->zko_attr_list[attr_num];
+}
+
+static int
+zfs_kobj_init(zfs_mod_kobj_t *zkobj, int attr_cnt, int child_cnt,
+    sysfs_show_func show_func)
+{
+	/*
+	 * Initialize object's attributes. Count can be zero.
+	 */
+	if (attr_cnt > 0) {
+		zkobj->zko_attr_list = kmem_zalloc(ATTR_TABLE_SIZE(attr_cnt),
+		    KM_SLEEP);
+		if (zkobj->zko_attr_list == NULL)
+			return (ENOMEM);
+	}
+	/* this will always have at least one slot for NULL termination */
+	zkobj->zko_default_attrs = kmem_zalloc(DEFAULT_ATTR_SIZE(attr_cnt),
+	    KM_SLEEP);
+	if (zkobj->zko_default_attrs == NULL) {
+		if (zkobj->zko_attr_list) {
+			kmem_free(zkobj->zko_attr_list,
+			    ATTR_TABLE_SIZE(attr_cnt));
+		}
+		return (ENOMEM);
+	}
+	zkobj->zko_attr_count = attr_cnt;
+	zkobj->zko_kobj_type.default_attrs = zkobj->zko_default_attrs;
+
+	if (child_cnt > 0) {
+		zkobj->zko_children = kmem_zalloc(CHILD_TABLE_SIZE(child_cnt),
+		    KM_SLEEP);
+		if (zkobj->zko_children == NULL) {
+			if (attr_cnt > 0) {
+				kmem_free(zkobj->zko_attr_list,
+				    DEFAULT_ATTR_SIZE(attr_cnt));
+				kmem_free(zkobj->zko_attr_list,
+				    ATTR_TABLE_SIZE(attr_cnt));
+			}
+			return (ENOMEM);
+		}
+		zkobj->zko_child_count = child_cnt;
+	}
+
+	zkobj->zko_sysfs_ops.show = show_func;
+	zkobj->zko_kobj_type.sysfs_ops = &zkobj->zko_sysfs_ops;
+	zkobj->zko_kobj_type.release = zfs_kobj_release;
+
+	return (0);
+}
+
+static int
+zfs_kobj_add(zfs_mod_kobj_t *zkobj, struct kobject *parent, const char *name)
+{
+	/* zko_default_attrs must be NULL terminated */
+	ASSERT(zkobj->zko_default_attrs != NULL);
+	ASSERT(zkobj->zko_default_attrs[zkobj->zko_attr_count] == NULL);
+
+	kobject_init(&zkobj->zko_kobj, &zkobj->zko_kobj_type);
+	return (kobject_add(&zkobj->zko_kobj, parent, name));
+}
+
+/*
+ * Each zfs property has these common attributes
+ */
+static const char *zprop_attrs[]  = {
+	"type",
+	"readonly",
+	"setonce",
+	"visible",
+	"values",
+	"default",
+	"datasets"	/* zfs properties only */
+};
+
+#define	ZFS_PROP_ATTR_COUNT	ARRAY_SIZE(zprop_attrs)
+#define	ZPOOL_PROP_ATTR_COUNT	(ZFS_PROP_ATTR_COUNT - 1)
+
+static const char *zprop_types[]  = {
+	"number",
+	"string",
+	"index",
+};
+
+typedef struct zfs_type_map {
+	zfs_type_t	ztm_type;
+	const char	*ztm_name;
+} zfs_type_map_t;
+
+static zfs_type_map_t type_map[] = {
+	{ZFS_TYPE_FILESYSTEM,	"filesystem"},
+	{ZFS_TYPE_SNAPSHOT,	"snapshot"},
+	{ZFS_TYPE_VOLUME,	"volume"},
+	{ZFS_TYPE_BOOKMARK,	"bookmark"}
+};
+
+/*
+ * Show the content for a zfs property attribute
+ */
+static ssize_t
+zprop_sysfs_show(const char *attr_name, const zprop_desc_t *property,
+    char *buf, size_t buflen)
+{
+	const char *show_str;
+
+	/* For dataset properties list the dataset types that apply */
+	if (strcmp(attr_name, "datasets") == 0 &&
+	    property->pd_types != ZFS_TYPE_POOL) {
+		int len = 0;
+
+		for (int i = 0; i < ARRAY_SIZE(type_map); i++) {
+			if (type_map[i].ztm_type & property->pd_types)  {
+				len += snprintf(buf + len, buflen - len, "%s ",
+				    type_map[i].ztm_name);
+			}
+		}
+		len += snprintf(buf + len, buflen - len, "\n");
+		return (len);
+	}
+
+	if (strcmp(attr_name, "type") == 0) {
+		show_str = zprop_types[property->pd_proptype];
+	} else if (strcmp(attr_name, "readonly") == 0) {
+		show_str = property->pd_attr == PROP_READONLY ? "1" : "0";
+	} else if (strcmp(attr_name, "setonce") == 0) {
+		show_str = property->pd_attr == PROP_ONETIME ? "1" : "0";
+	} else if (strcmp(attr_name, "visible") == 0) {
+		show_str = property->pd_visible ? "1" : "0";
+	} else if (strcmp(attr_name, "values") == 0) {
+		show_str = property->pd_values ? property->pd_values : "";
+	} else if (strcmp(attr_name, "default") == 0) {
+		char number[32];
+
+		switch (property->pd_proptype) {
+		case PROP_TYPE_NUMBER:
+			(void) snprintf(number, sizeof (number), "%llu",
+			    (u_longlong_t)property->pd_numdefault);
+			show_str = number;
+			break;
+		case PROP_TYPE_STRING:
+			show_str = property->pd_strdefault ?
+			    property->pd_strdefault : "";
+			break;
+		case PROP_TYPE_INDEX:
+			(void) zprop_index_to_string(property->pd_propnum,
+			    property->pd_numdefault, &show_str,
+			    property->pd_types);
+			break;
+		default:
+			return (0);
+		}
+	} else {
+		return (0);
+	}
+
+	return (snprintf(buf, buflen, "%s\n", show_str));
+}
+
+static ssize_t
+dataset_property_show(struct kobject *kobj, struct attribute *attr, char *buf)
+{
+	zfs_prop_t prop = zfs_name_to_prop(kobject_name(kobj));
+	zprop_desc_t *prop_tbl = zfs_prop_get_table();
+	ssize_t len;
+
+	ASSERT3U(prop, <, ZFS_NUM_PROPS);
+
+	len = zprop_sysfs_show(attr->name, &prop_tbl[prop], buf, PAGE_SIZE);
+
+	return (len);
+}
+
+static ssize_t
+pool_property_show(struct kobject *kobj, struct attribute *attr, char *buf)
+{
+	zpool_prop_t prop = zpool_name_to_prop(kobject_name(kobj));
+	zprop_desc_t *prop_tbl = zpool_prop_get_table();
+	ssize_t len;
+
+	ASSERT3U(prop, <, ZPOOL_NUM_PROPS);
+
+	len = zprop_sysfs_show(attr->name, &prop_tbl[prop], buf, PAGE_SIZE);
+
+	return (len);
+}
+
+/*
+ * ZFS kernel feature attributes for '/sys/module/zfs/features.kernel'
+ *
+ * This list is intended for kernel features that don't have a pool feature
+ * association or that extend existing user kernel interfaces.
+ *
+ * A user processes can easily check if the running zfs kernel module
+ * supports the new feature.
+ *
+ * For example, the initial channel_program feature was extended to support
+ * async calls (i.e. a sync flag). If this mechanism were in place at that
+ * time, we could have added a 'channel_program_async' to this list.
+ */
+static const char *zfs_features[]  = {
+	/* --> Add new kernel features here (post ZoL 0.8.0) */
+};
+
+#define	ZFS_FEATURE_COUNT	ARRAY_SIZE(zfs_features)
+
+static ssize_t
+kernel_feature_show(struct kobject *kobj, struct attribute *attr, char *buf)
+{
+	return (snprintf(buf, PAGE_SIZE, "supported\n"));
+}
+
+static int
+zfs_kernel_features_init(zfs_mod_kobj_t *zfs_kobj, struct kobject *parent)
+{
+	int err;
+
+	err = zfs_kobj_init(zfs_kobj, ZFS_FEATURE_COUNT, 0,
+	    kernel_feature_show);
+	if (err)
+		return (err);
+
+	for (int f = 0; f < ZFS_FEATURE_COUNT; f++)
+		zfs_kobj_add_attr(zfs_kobj, f, zfs_features[f]);
+
+	err = zfs_kobj_add(zfs_kobj, parent, ZFS_SYSFS_KERNEL_FEATURES);
+	if (err)
+		zfs_kobj_release(&zfs_kobj->zko_kobj);
+
+	return (err);
+}
+
+/*
+ * Each pool feature has these common attributes
+ */
+static const char *pool_feature_attrs[]  = {
+	"description",
+	"guid",
+	"uname",
+	"readonly_compatible",
+	"required_for_mos",
+	"activate_on_enable",
+	"per_dataset"
+};
+
+#define	ZPOOL_FEATURE_ATTR_COUNT	ARRAY_SIZE(pool_feature_attrs)
+
+/*
+ * Show the content for the given zfs pool feature attribute
+ */
+static ssize_t
+pool_feature_show(struct kobject *kobj, struct attribute *attr, char *buf)
+{
+	spa_feature_t fid;
+
+	if (zfeature_lookup_guid(kobject_name(kobj), &fid) != 0)
+		return (0);
+
+	ASSERT3U(fid, <, SPA_FEATURES);
+
+	zfeature_flags_t flags = spa_feature_table[fid].fi_flags;
+	const char *show_str = NULL;
+
+	if (strcmp(attr->name, "description") == 0) {
+		show_str = spa_feature_table[fid].fi_desc;
+	} else if (strcmp(attr->name, "guid") == 0) {
+		show_str = spa_feature_table[fid].fi_guid;
+	} else if (strcmp(attr->name, "uname") == 0) {
+		show_str = spa_feature_table[fid].fi_uname;
+	} else if (strcmp(attr->name, "readonly_compatible") == 0) {
+		show_str = flags & ZFEATURE_FLAG_READONLY_COMPAT ? "1" : "0";
+	} else if (strcmp(attr->name, "required_for_mos") == 0) {
+		show_str = flags & ZFEATURE_FLAG_MOS ? "1" : "0";
+	} else if (strcmp(attr->name, "activate_on_enable") == 0) {
+		show_str = flags & ZFEATURE_FLAG_ACTIVATE_ON_ENABLE ? "1" : "0";
+	} else if (strcmp(attr->name, "per_dataset") == 0) {
+		show_str = flags & ZFEATURE_FLAG_PER_DATASET ? "1" : "0";
+	}
+	if (show_str == NULL)
+		return (0);
+
+	return (snprintf(buf, PAGE_SIZE, "%s\n", show_str));
+}
+
+static void
+pool_feature_to_kobj(zfs_mod_kobj_t *parent, spa_feature_t fid,
+    const char *name)
+{
+	zfs_mod_kobj_t *zfs_kobj = &parent->zko_children[fid];
+
+	ASSERT3U(fid, <, SPA_FEATURES);
+	ASSERT(name);
+
+	int err = zfs_kobj_init(zfs_kobj, ZPOOL_FEATURE_ATTR_COUNT, 0,
+	    pool_feature_show);
+	if (err)
+		return;
+
+	for (int i = 0; i < ZPOOL_FEATURE_ATTR_COUNT; i++)
+		zfs_kobj_add_attr(zfs_kobj, i, pool_feature_attrs[i]);
+
+	err = zfs_kobj_add(zfs_kobj, &parent->zko_kobj, name);
+	if (err)
+		zfs_kobj_release(&zfs_kobj->zko_kobj);
+}
+
+static int
+zfs_pool_features_init(zfs_mod_kobj_t *zfs_kobj, struct kobject *parent)
+{
+	/*
+	 * Create a parent kobject to host pool features.
+	 *
+	 * '/sys/module/zfs/features.pool'
+	 */
+	int err = zfs_kobj_init(zfs_kobj, 0, SPA_FEATURES, pool_feature_show);
+	if (err)
+		return (err);
+	err = zfs_kobj_add(zfs_kobj, parent, ZFS_SYSFS_POOL_FEATURES);
+	if (err) {
+		zfs_kobj_release(&zfs_kobj->zko_kobj);
+		return (err);
+	}
+
+	/*
+	 * Now create a kobject for each feature.
+	 *
+	 * '/sys/module/zfs/features.pool/<feature>'
+	 */
+	for (spa_feature_t i = 0; i < SPA_FEATURES; i++)
+		pool_feature_to_kobj(zfs_kobj, i, spa_feature_table[i].fi_guid);
+
+	return (0);
+}
+
+typedef struct prop_to_kobj_arg {
+	zprop_desc_t	*p2k_table;
+	zfs_mod_kobj_t	*p2k_parent;
+	sysfs_show_func	p2k_show_func;
+	int		p2k_attr_count;
+} prop_to_kobj_arg_t;
+
+static int
+zprop_to_kobj(int prop, void *args)
+{
+	prop_to_kobj_arg_t *data = args;
+	zfs_mod_kobj_t *parent = data->p2k_parent;
+	zfs_mod_kobj_t *zfs_kobj = &parent->zko_children[prop];
+	const char *name = data->p2k_table[prop].pd_name;
+	int err;
+
+	ASSERT(name);
+
+	err = zfs_kobj_init(zfs_kobj, data->p2k_attr_count, 0,
+	    data->p2k_show_func);
+	if (err)
+		return (ZPROP_CONT);
+
+	for (int i = 0; i < data->p2k_attr_count; i++)
+		zfs_kobj_add_attr(zfs_kobj, i, zprop_attrs[i]);
+
+	err = zfs_kobj_add(zfs_kobj, &parent->zko_kobj, name);
+	if (err)
+		zfs_kobj_release(&zfs_kobj->zko_kobj);
+
+	return (ZPROP_CONT);
+}
+
+static int
+zfs_sysfs_properties_init(zfs_mod_kobj_t *zfs_kobj, struct kobject *parent,
+    zfs_type_t type)
+{
+	prop_to_kobj_arg_t context;
+	const char *name;
+	int err;
+
+	/*
+	 * Create a parent kobject to host properties.
+	 *
+	 * '/sys/module/zfs/properties.<type>'
+	 */
+	if (type == ZFS_TYPE_POOL) {
+		name = ZFS_SYSFS_POOL_PROPERTIES;
+		context.p2k_table = zpool_prop_get_table();
+		context.p2k_attr_count = ZPOOL_PROP_ATTR_COUNT;
+		context.p2k_parent = zfs_kobj;
+		context.p2k_show_func = pool_property_show;
+		err = zfs_kobj_init(zfs_kobj, 0, ZPOOL_NUM_PROPS,
+		    pool_property_show);
+	} else {
+		name = ZFS_SYSFS_DATASET_PROPERTIES;
+		context.p2k_table = zfs_prop_get_table();
+		context.p2k_attr_count = ZFS_PROP_ATTR_COUNT;
+		context.p2k_parent = zfs_kobj;
+		context.p2k_show_func = dataset_property_show;
+		err = zfs_kobj_init(zfs_kobj, 0, ZFS_NUM_PROPS,
+		    dataset_property_show);
+	}
+
+	if (err)
+		return (err);
+
+	err = zfs_kobj_add(zfs_kobj, parent, name);
+	if (err) {
+		zfs_kobj_release(&zfs_kobj->zko_kobj);
+		return (err);
+	}
+
+	/*
+	 * Create a kobject for each property.
+	 *
+	 * '/sys/module/zfs/properties.<type>/<property>'
+	 */
+	(void) zprop_iter_common(zprop_to_kobj, &context, B_TRUE,
+	    B_FALSE, type);
+
+	return (err);
+}
+
+void
+zfs_sysfs_init(void)
+{
+	struct kobject *parent =
+	    &(((struct module *)(THIS_MODULE))->mkobj).kobj;
+	int err;
+
+	ASSERT(parent != NULL);
+
+	err = zfs_kernel_features_init(&kernel_features_kobj, parent);
+	if (err)
+		return;
+
+	err = zfs_pool_features_init(&pool_features_kobj, parent);
+	if (err) {
+		zfs_kobj_fini(&kernel_features_kobj);
+		return;
+	}
+
+	err = zfs_sysfs_properties_init(&pool_props_kobj, parent,
+	    ZFS_TYPE_POOL);
+	if (err) {
+		zfs_kobj_fini(&kernel_features_kobj);
+		zfs_kobj_fini(&pool_features_kobj);
+		return;
+	}
+
+	err = zfs_sysfs_properties_init(&dataset_props_kobj, parent,
+	    ZFS_TYPE_FILESYSTEM);
+	if (err) {
+		zfs_kobj_fini(&kernel_features_kobj);
+		zfs_kobj_fini(&pool_features_kobj);
+		zfs_kobj_fini(&pool_props_kobj);
+		return;
+	}
+}
+
+void
+zfs_sysfs_fini(void)
+{
+	/*
+	 * Remove top-level kobjects; each will remove any children kobjects
+	 */
+	zfs_kobj_fini(&kernel_features_kobj);
+	zfs_kobj_fini(&pool_features_kobj);
+	zfs_kobj_fini(&dataset_props_kobj);
+	zfs_kobj_fini(&pool_props_kobj);
+}