Linux 5.18 compat: kobj_type.default_attrs replaced with default_groups

Upstream-commit: cdb4f26a63c391317e335e6e683a614358e70aeb ("kobject:
 kobj_type: remove default_attrs")
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#13357

config/kernel-sysfs.m4

@@ -0,0 +1,37 @@
+dnl #
+dnl # Linux 5.2/5.18 API
+dnl #
+dnl # In cdb4f26a63c391317e335e6e683a614358e70aeb ("kobject: kobj_type: remove default_attrs")
+dnl # 	struct kobj_type.default_attrs
+dnl # was finally removed in favour of
+dnl # 	struct kobj_type.default_groups
+dnl #
+dnl # This was added in aa30f47cf666111f6bbfd15f290a27e8a7b9d854 ("kobject: Add support for default attribute groups to kobj_type"),
+dnl # if both are present (5.2-5.17), we prefer default_groups; they're otherwise equivalent
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_SYSFS_DEFAULT_GROUPS], [
+	ZFS_LINUX_TEST_SRC([sysfs_default_groups], [
+		#include <linux/kobject.h>
+	],[
+		struct kobj_type __attribute__ ((unused)) kt = {
+			.default_groups = (const struct attribute_group **)NULL };
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_SYSFS_DEFAULT_GROUPS], [
+	AC_MSG_CHECKING([for struct kobj_type.default_groups])
+	ZFS_LINUX_TEST_RESULT([sysfs_default_groups],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE([HAVE_SYSFS_DEFAULT_GROUPS], 1, [struct kobj_type has default_groups])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_SRC_SYSFS], [
+	ZFS_AC_KERNEL_SRC_SYSFS_DEFAULT_GROUPS
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_SYSFS], [
+	ZFS_AC_KERNEL_SYSFS_DEFAULT_GROUPS
+])

config/kernel.m4

@@ -133,6 +133,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_BIO_MAX_SEGS
 	ZFS_AC_KERNEL_SRC_SIGNAL_STOP
 	ZFS_AC_KERNEL_SRC_SIGINFO
+	ZFS_AC_KERNEL_SRC_SYSFS
 	ZFS_AC_KERNEL_SRC_SET_SPECIAL_STATE
 	ZFS_AC_KERNEL_SRC_VFS_READPAGES
 	ZFS_AC_KERNEL_SRC_VFS_SET_PAGE_DIRTY_NOBUFFERS
@@ -247,6 +248,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_BIO_MAX_SEGS
 	ZFS_AC_KERNEL_SIGNAL_STOP
 	ZFS_AC_KERNEL_SIGINFO
+	ZFS_AC_KERNEL_SYSFS
 	ZFS_AC_KERNEL_SET_SPECIAL_STATE
 	ZFS_AC_KERNEL_VFS_READPAGES
 	ZFS_AC_KERNEL_VFS_SET_PAGE_DIRTY_NOBUFFERS

module/os/linux/zfs/zfs_sysfs.c

@@ -65,16 +65,15 @@
 /*
  * 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 */
+	struct attribute_group	zko_default_group;	/* .attrs allocated */
+	const struct attribute_group	*zko_default_groups[2];
 	size_t			zko_child_count;
 	zfs_mod_kobj_t		*zko_children;		/* allocated */
 };
@@ -127,10 +126,10 @@ zfs_kobj_release(struct kobject *kobj)
 		zkobj->zko_attr_list = NULL;
 	}
 
-	if (zkobj->zko_default_attrs != NULL) {
-		kmem_free(zkobj->zko_default_attrs,
+	if (zkobj->zko_default_group.attrs != NULL) {
+		kmem_free(zkobj->zko_default_group.attrs,
 		    DEFAULT_ATTR_SIZE(zkobj->zko_attr_count));
-		zkobj->zko_default_attrs = NULL;
+		zkobj->zko_default_group.attrs = NULL;
 	}
 
 	if (zkobj->zko_child_count != 0) {
@@ -154,11 +153,12 @@ 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);
+	ASSERT(zkobj->zko_default_group.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];
+	zkobj->zko_default_group.attrs[attr_num] =
+	    &zkobj->zko_attr_list[attr_num];
 	sysfs_attr_init(&zkobj->zko_attr_list[attr_num]);
 }
 
@@ -176,24 +176,29 @@ zfs_kobj_init(zfs_mod_kobj_t *zkobj, int attr_cnt, int child_cnt,
 			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) {
+	zkobj->zko_default_group.attrs =
+	    kmem_zalloc(DEFAULT_ATTR_SIZE(attr_cnt), KM_SLEEP);
+	if (zkobj->zko_default_group.attrs == NULL) {
 		if (zkobj->zko_attr_list != NULL) {
 			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;
+	zkobj->zko_default_groups[0] = &zkobj->zko_default_group;
+#ifdef HAVE_SYSFS_DEFAULT_GROUPS
+	zkobj->zko_kobj_type.default_groups = zkobj->zko_default_groups;
+#else
+	zkobj->zko_kobj_type.default_attrs = zkobj->zko_default_group.attrs;
+#endif
 
 	if (child_cnt > 0) {
 		zkobj->zko_children = kmem_zalloc(CHILD_TABLE_SIZE(child_cnt),
 		    KM_SLEEP);
 		if (zkobj->zko_children == NULL) {
-			if (zkobj->zko_default_attrs != NULL) {
-				kmem_free(zkobj->zko_default_attrs,
+			if (zkobj->zko_default_group.attrs != NULL) {
+				kmem_free(zkobj->zko_default_group.attrs,
 				    DEFAULT_ATTR_SIZE(attr_cnt));
 			}
 			if (zkobj->zko_attr_list != NULL) {
@@ -215,9 +220,9 @@ zfs_kobj_init(zfs_mod_kobj_t *zkobj, int attr_cnt, int child_cnt,
 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);
+	/* zko_default_group.attrs must be NULL terminated */
+	ASSERT(zkobj->zko_default_group.attrs != NULL);
+	ASSERT(zkobj->zko_default_group.attrs[zkobj->zko_attr_count] == NULL);
 
 	kobject_init(&zkobj->zko_kobj, &zkobj->zko_kobj_type);
 	return (kobject_add(&zkobj->zko_kobj, parent, name));