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 <mahrens@delphix.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Don Brady <don.brady@delphix.com>
Closes #7706

include/sys/Makefile.am

@@ -119,6 +119,7 @@ COMMON_H = \
 	$(top_srcdir)/include/sys/zfs_rlock.h \
 	$(top_srcdir)/include/sys/zfs_sa.h \
 	$(top_srcdir)/include/sys/zfs_stat.h \
+	$(top_srcdir)/include/sys/zfs_sysfs.h \
 	$(top_srcdir)/include/sys/zfs_vfsops.h \
 	$(top_srcdir)/include/sys/zfs_vnops.h \
 	$(top_srcdir)/include/sys/zfs_znode.h \

include/sys/zfs_sysfs.h

@@ -0,0 +1,47 @@
+/*
+ * 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.
+ */
+
+#ifndef	_SYS_ZFS_SYSFS_H
+#define	_SYS_ZFS_SYSFS_H
+
+#ifdef _KERNEL
+
+void zfs_sysfs_init(void);
+void zfs_sysfs_fini(void);
+
+#else
+
+#define	zfs_sysfs_init()
+#define	zfs_sysfs_fini()
+
+#endif
+
+#define	ZFS_SYSFS_POOL_PROPERTIES	"properties.pool"
+#define	ZFS_SYSFS_DATASET_PROPERTIES	"properties.dataset"
+#define	ZFS_SYSFS_KERNEL_FEATURES	"features.kernel"
+#define	ZFS_SYSFS_POOL_FEATURES		"features.pool"
+
+#define	ZFS_SYSFS_DIR			"/sys/module/zfs"
+
+#endif	/* _SYS_ZFS_SYSFS_H */

include/zfeature_common.h

@@ -85,6 +85,7 @@ typedef struct zfeature_info {
 	const char *fi_guid;	/* On-disk feature identifier */
 	const char *fi_desc;	/* Feature description */
 	zfeature_flags_t fi_flags;
+	boolean_t fi_zfs_mod_supported;	/* supported by running zfs module */
 	/* array of dependencies, terminated by SPA_FEATURE_NONE */
 	const spa_feature_t *fi_depends;
 } zfeature_info_t;
@@ -98,6 +99,7 @@ extern zfeature_info_t spa_feature_table[SPA_FEATURES];
 extern boolean_t zfeature_is_valid_guid(const char *);
 
 extern boolean_t zfeature_is_supported(const char *);
+extern int zfeature_lookup_guid(const char *, spa_feature_t *);
 extern int zfeature_lookup_name(const char *, spa_feature_t *);
 extern boolean_t zfeature_depends_on(spa_feature_t, spa_feature_t);
 

include/zfs_prop.h

@@ -78,6 +78,7 @@ typedef struct {
 	boolean_t pd_rightalign;	/* column alignment for "zfs list" */
 	boolean_t pd_visible;		/* do we list this property with the */
 					/* "zfs get" help message */
+	boolean_t pd_zfs_mod_supported;	/* supported by running zfs module */
 	const zprop_index_t *pd_table;	/* for index properties, a table */
 					/* defining the possible values */
 	size_t pd_table_size;		/* number of entries in pd_table[] */