zcommon: pre-iterate over sysfs instead of statting every feature

If sufficient memory (<2K, realistically) is available, libzfs_init()
can be significantly shorted by iterating over the correct sysfs
directory before registrations, we can turn 168 stats into 15/18
syscalls (3 opens (6 if built in), 3 fstats, 6 getdentses, and 3
closes), a tenfoldish reduction; this is probably a bit faster, too.

The list is always optional, and registration functions (and one-off
users) can simply pass NULL, which will fall back to the previous
mechanism

Also, don't allocate in zfs_mod_supported_impl, and use use access()
instead of stat(), since existence is really what we care about

Also, fix pre-prop-checking compat in fallback for built-in ZFS

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Tony Nguyen <[email protected]>
Signed-off-by: Ahelenia Ziemiańska <[email protected]>
Closes #12089 

1 files changed, 319 insertions, 218 deletions

diff --git a/module/zcommon/zfeature_common.c b/module/zcommon/zfeature_common.c
index 8d84c6d15..c7278fa00 100644
--- a/module/zcommon/zfeature_common.c
+++ b/module/zcommon/zfeature_common.c
@@ -32,6 +32,8 @@
 #ifndef _KERNEL
 #include <errno.h>
 #include <string.h>
+#include <dirent.h>
+#include <search.h>
 #include <sys/stat.h>
 #endif
 #include <sys/debug.h>
@@ -164,30 +166,109 @@ deps_contains_feature(const spa_feature_t *deps, const spa_feature_t feature)
 	return (B_FALSE);
 }
 
+#define	STRCMP ((int(*)(const void *, const void *))&strcmp)
+struct zfs_mod_supported_features {
+	void *tree;
+	boolean_t all_features;
+};
+
+struct zfs_mod_supported_features *
+zfs_mod_list_supported(const char *scope)
+{
+#if defined(__FreeBSD__) || defined(_KERNEL) || defined(LIB_ZPOOL_BUILD)
+	(void) scope;
+	return (NULL);
+#else
+	struct zfs_mod_supported_features *ret = calloc(1, sizeof (*ret));
+	if (ret == NULL)
+		return (NULL);
+
+	DIR *sysfs_dir = NULL;
+	char path[128];
+
+	if (snprintf(path, sizeof (path), "%s/%s",
+	    ZFS_SYSFS_DIR, scope) < sizeof (path))
+		sysfs_dir = opendir(path);
+	if (sysfs_dir == NULL && errno == ENOENT) {
+		if (snprintf(path, sizeof (path), "%s/%s",
+		    ZFS_SYSFS_ALT_DIR, scope) < sizeof (path))
+			sysfs_dir = opendir(path);
+	}
+	if (sysfs_dir == NULL) {
+		ret->all_features = errno == ENOENT &&
+		    (access(ZFS_SYSFS_DIR, F_OK) == 0 ||
+		    access(ZFS_SYSFS_ALT_DIR, F_OK) == 0);
+		return (ret);
+	}
+
+	struct dirent *node;
+	while ((node = readdir(sysfs_dir)) != NULL) {
+		if (strcmp(node->d_name, ".") == 0 ||
+		    strcmp(node->d_name, "..") == 0)
+			continue;
+
+		char *name = strdup(node->d_name);
+		if (name == NULL) {
+			goto nomem;
+		}
+
+		if (tsearch(name, &ret->tree, STRCMP) == NULL) {
+			/*
+			 * Don't bother checking for duplicate entries:
+			 * we're iterating a single directory.
+			 */
+			free(name);
+			goto nomem;
+		}
+	}
+
+end:
+	closedir(sysfs_dir);
+	return (ret);
+
+nomem:
+	zfs_mod_list_supported_free(ret);
+	ret = NULL;
+	goto end;
+#endif
+}
+
+void
+zfs_mod_list_supported_free(struct zfs_mod_supported_features *list)
+{
+#if !defined(__FreeBSD__) && !defined(_KERNEL) && !defined(LIB_ZPOOL_BUILD)
+	if (list) {
+		tdestroy(list->tree, free);
+		free(list);
+	}
+#else
+	(void) list;
+#endif
+}
+
 #if !defined(_KERNEL) && !defined(LIB_ZPOOL_BUILD)
 static boolean_t
 zfs_mod_supported_impl(const char *scope, const char *name, const char *sysfs)
 {
-	boolean_t supported = B_FALSE;
-	char *path;
-
-	int len = asprintf(&path, "%s%s%s%s%s", sysfs,
-	    scope == NULL ? "" : "/", scope == NULL ? "" : scope,
-	    name == NULL ? "" : "/", name == NULL ? "" : name);
-	if (len > 0) {
-		struct stat64 statbuf;
-		supported = !!(stat64(path, &statbuf) == 0);
-		free(path);
-	}
-
-	return (supported);
+	char path[128];
+	if (snprintf(path, sizeof (path), "%s%s%s%s%s", sysfs,
+	    scope == NULL ? "" : "/", scope ?: "",
+	    name == NULL ? "" : "/", name ?: "") < sizeof (path))
+		return (access(path, F_OK) == 0);
+	else
+		return (B_FALSE);
 }
 
 boolean_t
-zfs_mod_supported(const char *scope, const char *name)
+zfs_mod_supported(const char *scope, const char *name,
+    const struct zfs_mod_supported_features *sfeatures)
 {
 	boolean_t supported;
 
+	if (sfeatures != NULL)
+		return (sfeatures->all_features ||
+		    tfind(name, &sfeatures->tree, STRCMP));
+
 	/*
 	 * Check both the primary and alternate sysfs locations to determine
 	 * if the required functionality is supported.
@@ -202,10 +283,10 @@ zfs_mod_supported(const char *scope, const char *name)
 	 * scope directory does not exist.
 	 */
 	if (supported == B_FALSE) {
-		struct stat64 statbuf;
-		if ((stat64(ZFS_SYSFS_DIR, &statbuf) == 0) &&
-		    !zfs_mod_supported_impl(scope, NULL, ZFS_SYSFS_DIR) &&
-		    !zfs_mod_supported_impl(scope, NULL, ZFS_SYSFS_ALT_DIR)) {
+		if ((access(ZFS_SYSFS_DIR, F_OK) == 0 &&
+		    !zfs_mod_supported_impl(scope, NULL, ZFS_SYSFS_DIR)) ||
+		    (access(ZFS_SYSFS_ALT_DIR, F_OK) == 0 &&
+		    !zfs_mod_supported_impl(scope, NULL, ZFS_SYSFS_ALT_DIR))) {
 			supported = B_TRUE;
 		}
 	}
@@ -215,7 +296,8 @@ zfs_mod_supported(const char *scope, const char *name)
 #endif
 
 static boolean_t
-zfs_mod_supported_feature(const char *name)
+zfs_mod_supported_feature(const char *name,
+    const struct zfs_mod_supported_features *sfeatures)
 {
 	/*
 	 * The zfs module spa_feature_table[], whether in-kernel or in
@@ -229,17 +311,18 @@ zfs_mod_supported_feature(const char *name)
 	 */
 
 #if defined(_KERNEL) || defined(LIB_ZPOOL_BUILD) || defined(__FreeBSD__)
-	(void) name;
+	(void) name, (void) sfeatures;
 	return (B_TRUE);
 #else
-	return (zfs_mod_supported(ZFS_SYSFS_POOL_FEATURES, name));
+	return (zfs_mod_supported(ZFS_SYSFS_POOL_FEATURES, name, sfeatures));
 #endif
 }
 
 static void
 zfeature_register(spa_feature_t fid, const char *guid, const char *name,
     const char *desc, zfeature_flags_t flags, zfeature_type_t type,
-    const spa_feature_t *deps)
+    const spa_feature_t *deps,
+    const struct zfs_mod_supported_features *sfeatures)
 {
 	zfeature_info_t *feature = &spa_feature_table[fid];
 	static spa_feature_t nodeps[] = { SPA_FEATURE_NONE };
@@ -264,7 +347,8 @@ zfeature_register(spa_feature_t fid, const char *guid, const char *name,
 	feature->fi_flags = flags;
 	feature->fi_type = type;
 	feature->fi_depends = deps;
-	feature->fi_zfs_mod_supported = zfs_mod_supported_feature(guid);
+	feature->fi_zfs_mod_supported =
+	    zfs_mod_supported_feature(guid, sfeatures);
 }
 
 /*
@@ -283,318 +367,335 @@ zfeature_register(spa_feature_t fid, const char *guid, const char *name,
 void
 zpool_feature_init(void)
 {
+	struct zfs_mod_supported_features *sfeatures =
+	    zfs_mod_list_supported(ZFS_SYSFS_POOL_FEATURES);
+
 	zfeature_register(SPA_FEATURE_ASYNC_DESTROY,
 	    "com.delphix:async_destroy", "async_destroy",
 	    "Destroy filesystems asynchronously.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	zfeature_register(SPA_FEATURE_EMPTY_BPOBJ,
 	    "com.delphix:empty_bpobj", "empty_bpobj",
 	    "Snapshots use less space.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	zfeature_register(SPA_FEATURE_LZ4_COMPRESS,
 	    "org.illumos:lz4_compress", "lz4_compress",
 	    "LZ4 compression algorithm support.",
-	    ZFEATURE_FLAG_ACTIVATE_ON_ENABLE, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_ACTIVATE_ON_ENABLE, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	zfeature_register(SPA_FEATURE_MULTI_VDEV_CRASH_DUMP,
 	    "com.joyent:multi_vdev_crash_dump", "multi_vdev_crash_dump",
 	    "Crash dumps to multiple vdev pools.",
-	    0, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    0, ZFEATURE_TYPE_BOOLEAN, NULL, sfeatures);
 
 	zfeature_register(SPA_FEATURE_SPACEMAP_HISTOGRAM,
 	    "com.delphix:spacemap_histogram", "spacemap_histogram",
 	    "Spacemaps maintain space histograms.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	zfeature_register(SPA_FEATURE_ENABLED_TXG,
 	    "com.delphix:enabled_txg", "enabled_txg",
 	    "Record txg at which a feature is enabled",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	{
-	static const spa_feature_t hole_birth_deps[] = {
-		SPA_FEATURE_ENABLED_TXG,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_HOLE_BIRTH,
-	    "com.delphix:hole_birth", "hole_birth",
-	    "Retain hole birth txg for more precise zfs send",
-	    ZFEATURE_FLAG_MOS | ZFEATURE_FLAG_ACTIVATE_ON_ENABLE,
-	    ZFEATURE_TYPE_BOOLEAN, hole_birth_deps);
+		static const spa_feature_t hole_birth_deps[] = {
+			SPA_FEATURE_ENABLED_TXG,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_HOLE_BIRTH,
+		    "com.delphix:hole_birth", "hole_birth",
+		    "Retain hole birth txg for more precise zfs send",
+		    ZFEATURE_FLAG_MOS | ZFEATURE_FLAG_ACTIVATE_ON_ENABLE,
+		    ZFEATURE_TYPE_BOOLEAN, hole_birth_deps, sfeatures);
 	}
 
 	zfeature_register(SPA_FEATURE_POOL_CHECKPOINT,
 	    "com.delphix:zpool_checkpoint", "zpool_checkpoint",
 	    "Pool state can be checkpointed, allowing rewind later.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	zfeature_register(SPA_FEATURE_SPACEMAP_V2,
 	    "com.delphix:spacemap_v2", "spacemap_v2",
 	    "Space maps representing large segments are more efficient.",
 	    ZFEATURE_FLAG_READONLY_COMPAT | ZFEATURE_FLAG_ACTIVATE_ON_ENABLE,
-	    ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_TYPE_BOOLEAN, NULL, sfeatures);
 
 	zfeature_register(SPA_FEATURE_EXTENSIBLE_DATASET,
 	    "com.delphix:extensible_dataset", "extensible_dataset",
 	    "Enhanced dataset functionality, used by other features.",
-	    0, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    0, ZFEATURE_TYPE_BOOLEAN, NULL, sfeatures);
 
 	{
-	static const spa_feature_t bookmarks_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-
-	zfeature_register(SPA_FEATURE_BOOKMARKS,
-	    "com.delphix:bookmarks", "bookmarks",
-	    "\"zfs bookmark\" command",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
-	    bookmarks_deps);
+		static const spa_feature_t bookmarks_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+
+		zfeature_register(SPA_FEATURE_BOOKMARKS,
+		    "com.delphix:bookmarks", "bookmarks",
+		    "\"zfs bookmark\" command",
+		    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
+		    bookmarks_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t filesystem_limits_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_FS_SS_LIMIT,
-	    "com.joyent:filesystem_limits", "filesystem_limits",
-	    "Filesystem and snapshot limits.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
-	    filesystem_limits_deps);
+		static const spa_feature_t filesystem_limits_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_FS_SS_LIMIT,
+		    "com.joyent:filesystem_limits", "filesystem_limits",
+		    "Filesystem and snapshot limits.",
+		    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
+		    filesystem_limits_deps, sfeatures);
 	}
 
 	zfeature_register(SPA_FEATURE_EMBEDDED_DATA,
 	    "com.delphix:embedded_data", "embedded_data",
 	    "Blocks which compress very well use even less space.",
 	    ZFEATURE_FLAG_MOS | ZFEATURE_FLAG_ACTIVATE_ON_ENABLE,
-	    ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_TYPE_BOOLEAN, NULL, sfeatures);
 
 	{
-	static const spa_feature_t livelist_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_LIVELIST,
-	    "com.delphix:livelist", "livelist",
-	    "Improved clone deletion performance.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
-	    livelist_deps);
+		static const spa_feature_t livelist_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_LIVELIST,
+		    "com.delphix:livelist", "livelist",
+		    "Improved clone deletion performance.",
+		    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
+		    livelist_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t log_spacemap_deps[] = {
-		SPA_FEATURE_SPACEMAP_V2,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_LOG_SPACEMAP,
-	    "com.delphix:log_spacemap", "log_spacemap",
-	    "Log metaslab changes on a single spacemap and "
-	    "flush them periodically.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
-	    log_spacemap_deps);
+		static const spa_feature_t log_spacemap_deps[] = {
+			SPA_FEATURE_SPACEMAP_V2,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_LOG_SPACEMAP,
+		    "com.delphix:log_spacemap", "log_spacemap",
+		    "Log metaslab changes on a single spacemap and "
+		    "flush them periodically.",
+		    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
+		    log_spacemap_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t large_blocks_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_LARGE_BLOCKS,
-	    "org.open-zfs:large_blocks", "large_blocks",
-	    "Support for blocks larger than 128KB.",
-	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
-	    large_blocks_deps);
+		static const spa_feature_t large_blocks_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_LARGE_BLOCKS,
+		    "org.open-zfs:large_blocks", "large_blocks",
+		    "Support for blocks larger than 128KB.",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
+		    large_blocks_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t large_dnode_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_LARGE_DNODE,
-	    "org.zfsonlinux:large_dnode", "large_dnode",
-	    "Variable on-disk size of dnodes.",
-	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
-	    large_dnode_deps);
+		static const spa_feature_t large_dnode_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_LARGE_DNODE,
+		    "org.zfsonlinux:large_dnode", "large_dnode",
+		    "Variable on-disk size of dnodes.",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
+		    large_dnode_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t sha512_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_SHA512,
-	    "org.illumos:sha512", "sha512",
-	    "SHA-512/256 hash algorithm.",
-	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
-	    sha512_deps);
+		static const spa_feature_t sha512_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_SHA512,
+		    "org.illumos:sha512", "sha512",
+		    "SHA-512/256 hash algorithm.",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
+		    sha512_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t skein_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_SKEIN,
-	    "org.illumos:skein", "skein",
-	    "Skein hash algorithm.",
-	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
-	    skein_deps);
+		static const spa_feature_t skein_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_SKEIN,
+		    "org.illumos:skein", "skein",
+		    "Skein hash algorithm.",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
+		    skein_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t edonr_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_EDONR,
-	    "org.illumos:edonr", "edonr",
-	    "Edon-R hash algorithm.",
-	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
-	    edonr_deps);
+		static const spa_feature_t edonr_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_EDONR,
+		    "org.illumos:edonr", "edonr",
+		    "Edon-R hash algorithm.",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
+		    edonr_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t redact_books_deps[] = {
-		SPA_FEATURE_BOOKMARK_V2,
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_BOOKMARKS,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_REDACTION_BOOKMARKS,
-	    "com.delphix:redaction_bookmarks", "redaction_bookmarks",
-	    "Support for bookmarks which store redaction lists for zfs "
-	    "redacted send/recv.", 0, ZFEATURE_TYPE_BOOLEAN,
-	    redact_books_deps);
+		static const spa_feature_t redact_books_deps[] = {
+			SPA_FEATURE_BOOKMARK_V2,
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_BOOKMARKS,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_REDACTION_BOOKMARKS,
+		    "com.delphix:redaction_bookmarks", "redaction_bookmarks",
+		    "Support for bookmarks which store redaction lists for zfs "
+		    "redacted send/recv.", 0, ZFEATURE_TYPE_BOOLEAN,
+		    redact_books_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t redact_datasets_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_REDACTED_DATASETS,
-	    "com.delphix:redacted_datasets", "redacted_datasets", "Support for "
-	    "redacted datasets, produced by receiving a redacted zfs send "
-	    "stream.", ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_UINT64_ARRAY,
-	    redact_datasets_deps);
+		static const spa_feature_t redact_datasets_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_REDACTED_DATASETS,
+		    "com.delphix:redacted_datasets", "redacted_datasets",
+		    "Support for redacted datasets, produced by receiving "
+		    "a redacted zfs send stream.",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_UINT64_ARRAY,
+		    redact_datasets_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t bookmark_written_deps[] = {
-		SPA_FEATURE_BOOKMARK_V2,
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_BOOKMARKS,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_BOOKMARK_WRITTEN,
-	    "com.delphix:bookmark_written", "bookmark_written",
-	    "Additional accounting, enabling the written#<bookmark> property"
-	    "(space written since a bookmark), and estimates of send stream "
-	    "sizes for incrementals from bookmarks.",
-	    0, ZFEATURE_TYPE_BOOLEAN, bookmark_written_deps);
+		static const spa_feature_t bookmark_written_deps[] = {
+			SPA_FEATURE_BOOKMARK_V2,
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_BOOKMARKS,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_BOOKMARK_WRITTEN,
+		    "com.delphix:bookmark_written", "bookmark_written",
+		    "Additional accounting, enabling the written#<bookmark> "
+		    "property (space written since a bookmark), "
+		    "and estimates of send stream sizes for incrementals from "
+		    "bookmarks.",
+		    0, ZFEATURE_TYPE_BOOLEAN, bookmark_written_deps, sfeatures);
 	}
 
 	zfeature_register(SPA_FEATURE_DEVICE_REMOVAL,
 	    "com.delphix:device_removal", "device_removal",
 	    "Top-level vdevs can be removed, reducing logical pool size.",
-	    ZFEATURE_FLAG_MOS, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_MOS, ZFEATURE_TYPE_BOOLEAN, NULL, sfeatures);
 
 	{
-	static const spa_feature_t obsolete_counts_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_DEVICE_REMOVAL,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_OBSOLETE_COUNTS,
-	    "com.delphix:obsolete_counts", "obsolete_counts",
-	    "Reduce memory used by removed devices when their blocks are "
-	    "freed or remapped.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
-	    obsolete_counts_deps);
+		static const spa_feature_t obsolete_counts_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_DEVICE_REMOVAL,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_OBSOLETE_COUNTS,
+		    "com.delphix:obsolete_counts", "obsolete_counts",
+		    "Reduce memory used by removed devices when their blocks "
+		    "are freed or remapped.",
+		    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN,
+		    obsolete_counts_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t userobj_accounting_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_USEROBJ_ACCOUNTING,
-	    "org.zfsonlinux:userobj_accounting", "userobj_accounting",
-	    "User/Group object accounting.",
-	    ZFEATURE_FLAG_READONLY_COMPAT | ZFEATURE_FLAG_PER_DATASET,
-	    ZFEATURE_TYPE_BOOLEAN, userobj_accounting_deps);
+		static const spa_feature_t userobj_accounting_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_USEROBJ_ACCOUNTING,
+		    "org.zfsonlinux:userobj_accounting", "userobj_accounting",
+		    "User/Group object accounting.",
+		    ZFEATURE_FLAG_READONLY_COMPAT | ZFEATURE_FLAG_PER_DATASET,
+		    ZFEATURE_TYPE_BOOLEAN, userobj_accounting_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t bookmark_v2_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_BOOKMARKS,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_BOOKMARK_V2,
-	    "com.datto:bookmark_v2", "bookmark_v2",
-	    "Support for larger bookmarks",
-	    0, ZFEATURE_TYPE_BOOLEAN, bookmark_v2_deps);
+		static const spa_feature_t bookmark_v2_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_BOOKMARKS,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_BOOKMARK_V2,
+		    "com.datto:bookmark_v2", "bookmark_v2",
+		    "Support for larger bookmarks",
+		    0, ZFEATURE_TYPE_BOOLEAN, bookmark_v2_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t encryption_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_BOOKMARK_V2,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_ENCRYPTION,
-	    "com.datto:encryption", "encryption",
-	    "Support for dataset level encryption",
-	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
-	    encryption_deps);
+		static const spa_feature_t encryption_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_BOOKMARK_V2,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_ENCRYPTION,
+		    "com.datto:encryption", "encryption",
+		    "Support for dataset level encryption",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN,
+		    encryption_deps, sfeatures);
 	}
 
 	{
-	static const spa_feature_t project_quota_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_PROJECT_QUOTA,
-	    "org.zfsonlinux:project_quota", "project_quota",
-	    "space/object accounting based on project ID.",
-	    ZFEATURE_FLAG_READONLY_COMPAT | ZFEATURE_FLAG_PER_DATASET,
-	    ZFEATURE_TYPE_BOOLEAN, project_quota_deps);
+		static const spa_feature_t project_quota_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_PROJECT_QUOTA,
+		    "org.zfsonlinux:project_quota", "project_quota",
+		    "space/object accounting based on project ID.",
+		    ZFEATURE_FLAG_READONLY_COMPAT | ZFEATURE_FLAG_PER_DATASET,
+		    ZFEATURE_TYPE_BOOLEAN, project_quota_deps, sfeatures);
 	}
 
 	zfeature_register(SPA_FEATURE_ALLOCATION_CLASSES,
 	    "org.zfsonlinux:allocation_classes", "allocation_classes",
 	    "Support for separate allocation classes.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	zfeature_register(SPA_FEATURE_RESILVER_DEFER,
 	    "com.datto:resilver_defer", "resilver_defer",
 	    "Support for deferring new resilvers when one is already running.",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	zfeature_register(SPA_FEATURE_DEVICE_REBUILD,
 	    "org.openzfs:device_rebuild", "device_rebuild",
 	    "Support for sequential mirror/dRAID device rebuilds",
-	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
 
 	{
-	static const spa_feature_t zstd_deps[] = {
-		SPA_FEATURE_EXTENSIBLE_DATASET,
-		SPA_FEATURE_NONE
-	};
-	zfeature_register(SPA_FEATURE_ZSTD_COMPRESS,
-	    "org.freebsd:zstd_compress", "zstd_compress",
-	    "zstd compression algorithm support.",
-	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN, zstd_deps);
+		static const spa_feature_t zstd_deps[] = {
+			SPA_FEATURE_EXTENSIBLE_DATASET,
+			SPA_FEATURE_NONE
+		};
+		zfeature_register(SPA_FEATURE_ZSTD_COMPRESS,
+		    "org.freebsd:zstd_compress", "zstd_compress",
+		    "zstd compression algorithm support.",
+		    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN, zstd_deps,
+		    sfeatures);
 	}
 
 	zfeature_register(SPA_FEATURE_DRAID,
 	    "org.openzfs:draid", "draid", "Support for distributed spare RAID",
-	    ZFEATURE_FLAG_MOS, ZFEATURE_TYPE_BOOLEAN, NULL);
+	    ZFEATURE_FLAG_MOS, ZFEATURE_TYPE_BOOLEAN, NULL, sfeatures);
+
+	zfs_mod_list_supported_free(sfeatures);
 }
 
 #if defined(_KERNEL)