f2fs: introduce f2fs_base_attr for global sysfs entries

In /sys/fs/f2fs/features, there's no f2fs_sb_info, so let's avoid to get
the pointer.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/sysfs.c

@@ -61,6 +61,12 @@ struct f2fs_attr {
 	int id;
 };
 
+struct f2fs_base_attr {
+	struct attribute attr;
+	ssize_t (*show)(struct f2fs_base_attr *a, char *buf);
+	ssize_t (*store)(struct f2fs_base_attr *a, const char *buf, size_t len);
+};
+
 static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
 			     struct f2fs_sb_info *sbi, char *buf);
 
@@ -862,6 +868,25 @@ static void f2fs_sb_release(struct kobject *kobj)
 	complete(&sbi->s_kobj_unregister);
 }
 
+static ssize_t f2fs_base_attr_show(struct kobject *kobj,
+				struct attribute *attr, char *buf)
+{
+	struct f2fs_base_attr *a = container_of(attr,
+				struct f2fs_base_attr, attr);
+
+	return a->show ? a->show(a, buf) : 0;
+}
+
+static ssize_t f2fs_base_attr_store(struct kobject *kobj,
+				struct attribute *attr,
+				const char *buf, size_t len)
+{
+	struct f2fs_base_attr *a = container_of(attr,
+				struct f2fs_base_attr, attr);
+
+	return a->store ? a->store(a, buf, len) : 0;
+}
+
 /*
  * Note that there are three feature list entries:
  * 1) /sys/fs/f2fs/features
@@ -880,14 +905,13 @@ static void f2fs_sb_release(struct kobject *kobj)
  *     please add new on-disk feature in this list only.
  *     - ref. F2FS_SB_FEATURE_RO_ATTR()
  */
-static ssize_t f2fs_feature_show(struct f2fs_attr *a,
-		struct f2fs_sb_info *sbi, char *buf)
+static ssize_t f2fs_feature_show(struct f2fs_base_attr *a, char *buf)
 {
 	return sysfs_emit(buf, "supported\n");
 }
 
 #define F2FS_FEATURE_RO_ATTR(_name)				\
-static struct f2fs_attr f2fs_attr_##_name = {			\
+static struct f2fs_base_attr f2fs_base_attr_##_name = {		\
 	.attr = {.name = __stringify(_name), .mode = 0444 },	\
 	.show	= f2fs_feature_show,				\
 }
@@ -1256,37 +1280,38 @@ static struct attribute *f2fs_attrs[] = {
 };
 ATTRIBUTE_GROUPS(f2fs);
 
+#define BASE_ATTR_LIST(name) (&f2fs_base_attr_##name.attr)
 static struct attribute *f2fs_feat_attrs[] = {
 #ifdef CONFIG_FS_ENCRYPTION
-	ATTR_LIST(encryption),
-	ATTR_LIST(test_dummy_encryption_v2),
+	BASE_ATTR_LIST(encryption),
+	BASE_ATTR_LIST(test_dummy_encryption_v2),
 #if IS_ENABLED(CONFIG_UNICODE)
-	ATTR_LIST(encrypted_casefold),
+	BASE_ATTR_LIST(encrypted_casefold),
 #endif
 #endif /* CONFIG_FS_ENCRYPTION */
 #ifdef CONFIG_BLK_DEV_ZONED
-	ATTR_LIST(block_zoned),
+	BASE_ATTR_LIST(block_zoned),
 #endif
-	ATTR_LIST(atomic_write),
-	ATTR_LIST(extra_attr),
-	ATTR_LIST(project_quota),
-	ATTR_LIST(inode_checksum),
-	ATTR_LIST(flexible_inline_xattr),
-	ATTR_LIST(quota_ino),
-	ATTR_LIST(inode_crtime),
-	ATTR_LIST(lost_found),
+	BASE_ATTR_LIST(atomic_write),
+	BASE_ATTR_LIST(extra_attr),
+	BASE_ATTR_LIST(project_quota),
+	BASE_ATTR_LIST(inode_checksum),
+	BASE_ATTR_LIST(flexible_inline_xattr),
+	BASE_ATTR_LIST(quota_ino),
+	BASE_ATTR_LIST(inode_crtime),
+	BASE_ATTR_LIST(lost_found),
 #ifdef CONFIG_FS_VERITY
-	ATTR_LIST(verity),
+	BASE_ATTR_LIST(verity),
 #endif
-	ATTR_LIST(sb_checksum),
+	BASE_ATTR_LIST(sb_checksum),
 #if IS_ENABLED(CONFIG_UNICODE)
-	ATTR_LIST(casefold),
+	BASE_ATTR_LIST(casefold),
 #endif
-	ATTR_LIST(readonly),
+	BASE_ATTR_LIST(readonly),
 #ifdef CONFIG_F2FS_FS_COMPRESSION
-	ATTR_LIST(compression),
+	BASE_ATTR_LIST(compression),
 #endif
-	ATTR_LIST(pin_file),
+	BASE_ATTR_LIST(pin_file),
 	NULL,
 };
 ATTRIBUTE_GROUPS(f2fs_feat);
@@ -1362,9 +1387,14 @@ static struct kset f2fs_kset = {
 	.kobj	= {.ktype = &f2fs_ktype},
 };
 
+static const struct sysfs_ops f2fs_feat_attr_ops = {
+	.show	= f2fs_base_attr_show,
+	.store	= f2fs_base_attr_store,
+};
+
 static const struct kobj_type f2fs_feat_ktype = {
 	.default_groups = f2fs_feat_groups,
-	.sysfs_ops	= &f2fs_attr_ops,
+	.sysfs_ops	= &f2fs_feat_attr_ops,
 };
 
 static struct kobject f2fs_feat = {