/**
@file
@brief    Linux kernel memory management interface wrapper
@details  Copyright (c) 2025 Acronis International GmbH
@author   Denis Kopyrin ([email protected])
@since    $Id: $
*/

#include "memory.h"
#include "compat.h"

#include <linux/module.h>
#include <linux/kobject.h>

struct kmem_cache *g_handles_cache = NULL;
memory_metrics_t* g_memory_metrics = NULL;

struct metrics_attribute {
	struct attribute attr;
	ssize_t (*show)(memory_metrics_t* metrics, char *buf);
};

#define METRIC_X \
METRIC(total_file_contexts_tables) \
METRIC(total_transports) \
METRIC(total_transport_events) \
METRIC(total_msgs) \
METRIC(total_msgs_size) \
METRIC(total_sized_msgs) \
METRIC(total_sized_msgs_size)

#define METRICS_ATTR_RO(_name) \
static ssize_t _name##_show(memory_metrics_t* metrics, char *buf) \
{ \
	return sprintf(buf, "%ld\n", (long) atomic64_read(&metrics->_name)); \
} \
static const struct metrics_attribute s_metrics_attr_##_name = __ATTR_RO(_name)

#define METRIC(_name) METRICS_ATTR_RO(_name);
METRIC_X
#undef METRIC

static const struct attribute *s_metrics_attrs[] = {
#define METRIC(_name) &s_metrics_attr_##_name.attr,
METRIC_X
#undef METRIC
	NULL
};

#define to_metrics(_at) container_of(to_safe_kobject(_at), memory_metrics_t, skobj)
#define to_metrics_attr(_at) container_of(_at, struct metrics_attribute, attr)

static ssize_t metrics_show(struct kobject *kobj, struct attribute *attr, char *buf)
{
	memory_metrics_t* metrics = to_metrics(kobj);
	struct metrics_attribute *metrics_attr = to_metrics_attr(attr);
	return metrics_attr->show(metrics, buf);
}

const struct sysfs_ops s_metrics_sysfs_ops = {
	.show = metrics_show,
};

static struct kobj_type s_metrics_ktype = {
	.release = safe_kobject_sysfs_release,
	.sysfs_ops = &s_metrics_sysfs_ops,
};

static int sysfs_metrics_add(memory_metrics_t *metrics)
{
	return sysfs_create_files(&metrics->skobj.kobj, s_metrics_attrs);
}

int memory_init(void)
{
	int err;
	g_memory_metrics = mem_alloc(sizeof(memory_metrics_t));
	if (!g_memory_metrics) {
		return -ENOMEM;
	}

	g_handles_cache = kmem_cache_create("fileprotector_file_handle", MAX_HANDLE_SZ, 0, 0, NULL);
	if (!g_handles_cache) {
		mem_free(g_memory_metrics);
		return -ENOMEM;
	}

#define METRIC(_name) atomic64_set(&g_memory_metrics->_name, 0);
METRIC_X
#undef METRIC

	safe_kobject_init(&g_memory_metrics->skobj);
	err = kobject_init_and_add(&g_memory_metrics->skobj.kobj, &s_metrics_ktype, &THIS_MODULE->mkobj.kobj, "metrics");
	if (err) {
		// If 'init_and_add' fails, it really means that 'add' has failed
		// 'put' without wait will suffice because 'sysfs' does not see metrics yet
		kobject_put(&g_memory_metrics->skobj.kobj);
		goto fail;
	}

	err = sysfs_metrics_add(g_memory_metrics);
	if (err) {
		// Now we are required to use 'safe_kobject_del' because sysfs saw 'add' above.
		safe_kobject_del(&g_memory_metrics->skobj);
		goto fail;
	}

    return 0;

fail:
	mem_free(g_memory_metrics);
	kmem_cache_destroy(g_handles_cache);
	return err;
}

void memory_deinit(void)
{
	if (g_handles_cache) {
		kmem_cache_destroy(g_handles_cache);
	}

#ifdef KERNEL_MOCK
#define METRIC(_name) BUG_ON(atomic64_read(&g_memory_metrics->_name));
METRIC_X
#undef METRIC
#endif

	if (g_memory_metrics) {
		sysfs_remove_files(&g_memory_metrics->skobj.kobj, s_metrics_attrs);
		safe_kobject_del(&g_memory_metrics->skobj);
		mem_free(g_memory_metrics);
	}
}