Fix in-kernel sysfs entries

The recent sysfs zfs properties feature breaks the in-kernel
builds of zfs (sans module).  When not built as a module add
the sysfs entries under /sys/fs/zfs/.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Don Brady <don.brady@delphix.com>
Closes #7868 
Closes #7872

include/sys/zfs_sysfs.h

@@ -35,6 +35,7 @@ void zfs_sysfs_fini(void);
 #define	zfs_sysfs_init()
 #define	zfs_sysfs_fini()
 
+boolean_t zfs_mod_supported(const char *, const char *);
 #endif
 
 #define	ZFS_SYSFS_POOL_PROPERTIES	"properties.pool"
@@ -43,5 +44,7 @@ void zfs_sysfs_fini(void);
 #define	ZFS_SYSFS_POOL_FEATURES		"features.pool"
 
 #define	ZFS_SYSFS_DIR			"/sys/module/zfs"
+/* Alternate location when ZFS is built as part of the kernel (rare) */
+#define	ZFS_SYSFS_ALT_DIR		"/sys/fs/zfs"
 
 #endif	/* _SYS_ZFS_SYSFS_H */

module/zcommon/zfeature_common.c

@@ -159,6 +159,32 @@ deps_contains_feature(const spa_feature_t *deps, const spa_feature_t feature)
 	return (B_FALSE);
 }
 
+#if !defined(_KERNEL) && !defined(LIB_ZPOOL_BUILD)
+static boolean_t
+zfs_mod_supported_impl(const char *scope, const char *name, const char *sysfs)
+{
+	struct stat64 statbuf;
+	char *path;
+	boolean_t supported = B_FALSE;
+	int len;
+
+	len = asprintf(&path, "%s/%s/%s", sysfs, scope, name);
+
+	if (len > 0) {
+		supported = !!(stat64(path, &statbuf) == 0);
+		free(path);
+	}
+	return (supported);
+}
+
+boolean_t
+zfs_mod_supported(const char *scope, const char *name)
+{
+	return (zfs_mod_supported_impl(scope, name, ZFS_SYSFS_DIR) ||
+	    zfs_mod_supported_impl(scope, name, ZFS_SYSFS_ALT_DIR));
+}
+#endif
+
 static boolean_t
 zfs_mod_supported_feature(const char *name)
 {
@@ -171,19 +197,7 @@ zfs_mod_supported_feature(const char *name)
 #if defined(_KERNEL) || defined(LIB_ZPOOL_BUILD)
 	return (B_TRUE);
 #else
-	struct stat64 statbuf;
+	return (zfs_mod_supported(ZFS_SYSFS_POOL_FEATURES, name));
-	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
 }
 

module/zcommon/zprop_common.c

@@ -81,20 +81,8 @@ zfs_mod_supported_prop(const char *name, zfs_type_t type)
 #if defined(_KERNEL) || defined(LIB_ZPOOL_BUILD)
 	return (B_TRUE);
 #else
-	struct stat64 statbuf;
+	return (zfs_mod_supported(type == ZFS_TYPE_POOL ?
-	char *path;
+	    ZFS_SYSFS_POOL_PROPERTIES : ZFS_SYSFS_DATASET_PROPERTIES, name));
-	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
 }
 

module/zfs/zfs_sysfs.c

@@ -572,11 +572,16 @@ zfs_sysfs_properties_init(zfs_mod_kobj_t *zfs_kobj, struct kobject *parent,
 void
 zfs_sysfs_init(void)
 {
-	struct kobject *parent =
+	struct kobject *parent;
-	    &(((struct module *)(THIS_MODULE))->mkobj).kobj;
+#if defined(CONFIG_ZFS) && !defined(CONFIG_ZFS_MODULE)
+	parent = kobject_create_and_add("zfs", fs_kobj);
+#else
+	parent = &(((struct module *)(THIS_MODULE))->mkobj).kobj;
+#endif
 	int err;
 
-	ASSERT(parent != NULL);
+	if (parent == NULL)
+		return;
 
 	err = zfs_kernel_features_init(&kernel_features_kobj, parent);
 	if (err)