// SPDX-License-Identifier: GPL-2.0
/*
 * Simple file system for zoned block devices exposing zones as files.
 *
 * Copyright (C) 2022 Western Digital Corporation or its affiliates.
 */
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/blkdev.h>

#include "zonefs.h"

struct zonefs_sysfs_attr {
        struct attribute attr;
        ssize_t (*show)(struct zonefs_sb_info *sbi, char *buf);
};

#define ZONEFS_SYSFS_ATTR_RO(name) \
static struct zonefs_sysfs_attr zonefs_sysfs_attr_##name = __ATTR_RO(name)

#define ATTR_LIST(name) &zonefs_sysfs_attr_##name.attr

static ssize_t zonefs_sysfs_attr_show(struct kobject *kobj,
                                      struct attribute *attr, char *buf)
{
        struct zonefs_sb_info *sbi =
                container_of(kobj, struct zonefs_sb_info, s_kobj);
        struct zonefs_sysfs_attr *zonefs_attr =
                container_of(attr, struct zonefs_sysfs_attr, attr);

        if (!zonefs_attr->show)
                return 0;

        return zonefs_attr->show(sbi, buf);
}

static ssize_t max_wro_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
{
        return sysfs_emit(buf, "%u\n", sbi->s_max_wro_seq_files);
}
ZONEFS_SYSFS_ATTR_RO(max_wro_seq_files);

static ssize_t nr_wro_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
{
        return sysfs_emit(buf, "%d\n", atomic_read(&sbi->s_wro_seq_files));
}
ZONEFS_SYSFS_ATTR_RO(nr_wro_seq_files);

static ssize_t max_active_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
{
        return sysfs_emit(buf, "%u\n", sbi->s_max_active_seq_files);
}
ZONEFS_SYSFS_ATTR_RO(max_active_seq_files);

static ssize_t nr_active_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
{
        return sysfs_emit(buf, "%d\n", atomic_read(&sbi->s_active_seq_files));
}
ZONEFS_SYSFS_ATTR_RO(nr_active_seq_files);

static struct attribute *zonefs_sysfs_attrs[] = {
        ATTR_LIST(max_wro_seq_files),
        ATTR_LIST(nr_wro_seq_files),
        ATTR_LIST(max_active_seq_files),
        ATTR_LIST(nr_active_seq_files),
        NULL,
};
ATTRIBUTE_GROUPS(zonefs_sysfs);

static void zonefs_sysfs_sb_release(struct kobject *kobj)
{
        struct zonefs_sb_info *sbi =
                container_of(kobj, struct zonefs_sb_info, s_kobj);

        complete(&sbi->s_kobj_unregister);
}

static const struct sysfs_ops zonefs_sysfs_attr_ops = {
        .show   = zonefs_sysfs_attr_show,
};

static const struct kobj_type zonefs_sb_ktype = {
        .default_groups = zonefs_sysfs_groups,
        .sysfs_ops      = &zonefs_sysfs_attr_ops,
        .release        = zonefs_sysfs_sb_release,
};

static struct kobject *zonefs_sysfs_root;

int zonefs_sysfs_register(struct super_block *sb)
{
        struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
        int ret;

        super_set_sysfs_name_id(sb);
        init_completion(&sbi->s_kobj_unregister);
        ret = kobject_init_and_add(&sbi->s_kobj, &zonefs_sb_ktype,
                                   zonefs_sysfs_root, "%s", sb->s_id);
        if (ret) {
                kobject_put(&sbi->s_kobj);
                wait_for_completion(&sbi->s_kobj_unregister);
                return ret;
        }

        sbi->s_sysfs_registered = true;

        return 0;
}

void zonefs_sysfs_unregister(struct super_block *sb)
{
        struct zonefs_sb_info *sbi = ZONEFS_SB(sb);

        if (!sbi || !sbi->s_sysfs_registered)
                return;

        kobject_del(&sbi->s_kobj);
        kobject_put(&sbi->s_kobj);
        wait_for_completion(&sbi->s_kobj_unregister);
}

int __init zonefs_sysfs_init(void)
{
        zonefs_sysfs_root = kobject_create_and_add("zonefs", fs_kobj);
        if (!zonefs_sysfs_root)
                return -ENOMEM;

        return 0;
}

void zonefs_sysfs_exit(void)
{
        kobject_put(zonefs_sysfs_root);
        zonefs_sysfs_root = NULL;
}