erofs: add sysfs interface

Add sysfs interface to configure erofs related parameters later.

Link: https://lore.kernel.org/r/20211201145436.4357-1-huangjianan@oppo.com
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 239 insertions, 0 deletions

diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
new file mode 100644
index 000000000000..33e15fa63c82
--- /dev/null
+++ b/fs/erofs/sysfs.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C), 2008-2021, OPPO Mobile Comm Corp., Ltd.
+ *             https://www.oppo.com/
+ */
+#include <linux/sysfs.h>
+#include <linux/kobject.h>
+
+#include "internal.h"
+
+enum {
+	attr_feature,
+	attr_pointer_ui,
+	attr_pointer_bool,
+};
+
+enum {
+	struct_erofs_sb_info,
+};
+
+struct erofs_attr {
+	struct attribute attr;
+	short attr_id;
+	int struct_type, offset;
+};
+
+#define EROFS_ATTR(_name, _mode, _id)					\
+static struct erofs_attr erofs_attr_##_name = {				\
+	.attr = {.name = __stringify(_name), .mode = _mode },		\
+	.attr_id = attr_##_id,						\
+}
+#define EROFS_ATTR_FUNC(_name, _mode)	EROFS_ATTR(_name, _mode, _name)
+#define EROFS_ATTR_FEATURE(_name)	EROFS_ATTR(_name, 0444, feature)
+
+#define EROFS_ATTR_OFFSET(_name, _mode, _id, _struct)	\
+static struct erofs_attr erofs_attr_##_name = {			\
+	.attr = {.name = __stringify(_name), .mode = _mode },	\
+	.attr_id = attr_##_id,					\
+	.struct_type = struct_##_struct,			\
+	.offset = offsetof(struct _struct, _name),\
+}
+
+#define EROFS_ATTR_RW(_name, _id, _struct)	\
+	EROFS_ATTR_OFFSET(_name, 0644, _id, _struct)
+
+#define EROFS_RO_ATTR(_name, _id, _struct)	\
+	EROFS_ATTR_OFFSET(_name, 0444, _id, _struct)
+
+#define EROFS_ATTR_RW_UI(_name, _struct)	\
+	EROFS_ATTR_RW(_name, pointer_ui, _struct)
+
+#define EROFS_ATTR_RW_BOOL(_name, _struct)	\
+	EROFS_ATTR_RW(_name, pointer_bool, _struct)
+
+#define ATTR_LIST(name) (&erofs_attr_##name.attr)
+
+static struct attribute *erofs_attrs[] = {
+	NULL,
+};
+ATTRIBUTE_GROUPS(erofs);
+
+/* Features this copy of erofs supports */
+EROFS_ATTR_FEATURE(zero_padding);
+EROFS_ATTR_FEATURE(compr_cfgs);
+EROFS_ATTR_FEATURE(big_pcluster);
+EROFS_ATTR_FEATURE(chunked_file);
+EROFS_ATTR_FEATURE(device_table);
+EROFS_ATTR_FEATURE(compr_head2);
+EROFS_ATTR_FEATURE(sb_chksum);
+
+static struct attribute *erofs_feat_attrs[] = {
+	ATTR_LIST(zero_padding),
+	ATTR_LIST(compr_cfgs),
+	ATTR_LIST(big_pcluster),
+	ATTR_LIST(chunked_file),
+	ATTR_LIST(device_table),
+	ATTR_LIST(compr_head2),
+	ATTR_LIST(sb_chksum),
+	NULL,
+};
+ATTRIBUTE_GROUPS(erofs_feat);
+
+static unsigned char *__struct_ptr(struct erofs_sb_info *sbi,
+					  int struct_type, int offset)
+{
+	if (struct_type == struct_erofs_sb_info)
+		return (unsigned char *)sbi + offset;
+	return NULL;
+}
+
+static ssize_t erofs_attr_show(struct kobject *kobj,
+				struct attribute *attr, char *buf)
+{
+	struct erofs_sb_info *sbi = container_of(kobj, struct erofs_sb_info,
+						s_kobj);
+	struct erofs_attr *a = container_of(attr, struct erofs_attr, attr);
+	unsigned char *ptr = __struct_ptr(sbi, a->struct_type, a->offset);
+
+	switch (a->attr_id) {
+	case attr_feature:
+		return sysfs_emit(buf, "supported\n");
+	case attr_pointer_ui:
+		if (!ptr)
+			return 0;
+		return sysfs_emit(buf, "%u\n", *(unsigned int *)ptr);
+	case attr_pointer_bool:
+		if (!ptr)
+			return 0;
+		return sysfs_emit(buf, "%d\n", *(bool *)ptr);
+	}
+	return 0;
+}
+
+static ssize_t erofs_attr_store(struct kobject *kobj, struct attribute *attr,
+						const char *buf, size_t len)
+{
+	struct erofs_sb_info *sbi = container_of(kobj, struct erofs_sb_info,
+						s_kobj);
+	struct erofs_attr *a = container_of(attr, struct erofs_attr, attr);
+	unsigned char *ptr = __struct_ptr(sbi, a->struct_type, a->offset);
+	unsigned long t;
+	int ret;
+
+	switch (a->attr_id) {
+	case attr_pointer_ui:
+		if (!ptr)
+			return 0;
+		ret = kstrtoul(skip_spaces(buf), 0, &t);
+		if (ret)
+			return ret;
+		if (t != (unsigned int)t)
+			return -ERANGE;
+		*(unsigned int *)ptr = t;
+		return len;
+	case attr_pointer_bool:
+		if (!ptr)
+			return 0;
+		ret = kstrtoul(skip_spaces(buf), 0, &t);
+		if (ret)
+			return ret;
+		if (t != 0 && t != 1)
+			return -EINVAL;
+		*(bool *)ptr = !!t;
+		return len;
+	}
+	return 0;
+}
+
+static void erofs_sb_release(struct kobject *kobj)
+{
+	struct erofs_sb_info *sbi = container_of(kobj, struct erofs_sb_info,
+						 s_kobj);
+	complete(&sbi->s_kobj_unregister);
+}
+
+static const struct sysfs_ops erofs_attr_ops = {
+	.show	= erofs_attr_show,
+	.store	= erofs_attr_store,
+};
+
+static struct kobj_type erofs_sb_ktype = {
+	.default_groups = erofs_groups,
+	.sysfs_ops	= &erofs_attr_ops,
+	.release	= erofs_sb_release,
+};
+
+static struct kobj_type erofs_ktype = {
+	.sysfs_ops	= &erofs_attr_ops,
+};
+
+static struct kset erofs_root = {
+	.kobj	= {.ktype = &erofs_ktype},
+};
+
+static struct kobj_type erofs_feat_ktype = {
+	.default_groups = erofs_feat_groups,
+	.sysfs_ops	= &erofs_attr_ops,
+};
+
+static struct kobject erofs_feat = {
+	.kset	= &erofs_root,
+};
+
+int erofs_register_sysfs(struct super_block *sb)
+{
+	struct erofs_sb_info *sbi = EROFS_SB(sb);
+	int err;
+
+	sbi->s_kobj.kset = &erofs_root;
+	init_completion(&sbi->s_kobj_unregister);
+	err = kobject_init_and_add(&sbi->s_kobj, &erofs_sb_ktype, NULL,
+				   "%s", sb->s_id);
+	if (err)
+		goto put_sb_kobj;
+	return 0;
+
+put_sb_kobj:
+	kobject_put(&sbi->s_kobj);
+	wait_for_completion(&sbi->s_kobj_unregister);
+	return err;
+}
+
+void erofs_unregister_sysfs(struct super_block *sb)
+{
+	struct erofs_sb_info *sbi = EROFS_SB(sb);
+
+	kobject_del(&sbi->s_kobj);
+	kobject_put(&sbi->s_kobj);
+	wait_for_completion(&sbi->s_kobj_unregister);
+}
+
+int __init erofs_init_sysfs(void)
+{
+	int ret;
+
+	kobject_set_name(&erofs_root.kobj, "erofs");
+	erofs_root.kobj.parent = fs_kobj;
+	ret = kset_register(&erofs_root);
+	if (ret)
+		goto root_err;
+
+	ret = kobject_init_and_add(&erofs_feat, &erofs_feat_ktype,
+				   NULL, "features");
+	if (ret)
+		goto feat_err;
+	return ret;
+
+feat_err:
+	kobject_put(&erofs_feat);
+	kset_unregister(&erofs_root);
+root_err:
+	return ret;
+}
+
+void erofs_exit_sysfs(void)
+{
+	kobject_put(&erofs_feat);
+	kset_unregister(&erofs_root);
+}