#include <net/tcp.h>
#include <net/tcp_memcontrol.h>
#include <net/sock.h>
#include <net/ip.h>
#include <linux/nsproxy.h>
#include <linux/memcontrol.h>
#include <linux/module.h>

int tcp_init_cgroup(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
{
	struct mem_cgroup *parent = parent_mem_cgroup(memcg);
	struct page_counter *counter_parent = NULL;
	/*
	 * The root cgroup does not use page_counters, but rather,
	 * rely on the data already collected by the network
	 * subsystem
	 */
	if (memcg == root_mem_cgroup)
		return 0;

	memcg->tcp_mem.memory_pressure = 0;

	if (parent)
		counter_parent = &parent->tcp_mem.memory_allocated;

	page_counter_init(&memcg->tcp_mem.memory_allocated, counter_parent);

	return 0;
}

void tcp_destroy_cgroup(struct mem_cgroup *memcg)
{
	if (memcg == root_mem_cgroup)
		return;

	if (memcg->tcp_mem.active)
		static_branch_dec(&memcg_sockets_enabled_key);
}

static int tcp_update_limit(struct mem_cgroup *memcg, unsigned long nr_pages)
{
	int ret;

	if (memcg == root_mem_cgroup)
		return -EINVAL;

	ret = page_counter_limit(&memcg->tcp_mem.memory_allocated, nr_pages);
	if (ret)
		return ret;

	if (!memcg->tcp_mem.active) {
		/*
		 * The active flag needs to be written after the static_key
		 * update. This is what guarantees that the socket activation
		 * function is the last one to run. See sock_update_memcg() for
		 * details, and note that we don't mark any socket as belonging
		 * to this memcg until that flag is up.
		 *
		 * We need to do this, because static_keys will span multiple
		 * sites, but we can't control their order. If we mark a socket
		 * as accounted, but the accounting functions are not patched in
		 * yet, we'll lose accounting.
		 *
		 * We never race with the readers in sock_update_memcg(),
		 * because when this value change, the code to process it is not
		 * patched in yet.
		 */
		static_branch_inc(&memcg_sockets_enabled_key);
		memcg->tcp_mem.active = true;
	}

	return 0;
}

enum {
	RES_USAGE,
	RES_LIMIT,
	RES_MAX_USAGE,
	RES_FAILCNT,
};

static DEFINE_MUTEX(tcp_limit_mutex);

static ssize_t tcp_cgroup_write(struct kernfs_open_file *of,
				char *buf, size_t nbytes, loff_t off)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
	unsigned long nr_pages;
	int ret = 0;

	buf = strstrip(buf);

	switch (of_cft(of)->private) {
	case RES_LIMIT:
		/* see memcontrol.c */
		ret = page_counter_memparse(buf, "-1", &nr_pages);
		if (ret)
			break;
		mutex_lock(&tcp_limit_mutex);
		ret = tcp_update_limit(memcg, nr_pages);
		mutex_unlock(&tcp_limit_mutex);
		break;
	default:
		ret = -EINVAL;
		break;
	}
	return ret ?: nbytes;
}

static u64 tcp_cgroup_read(struct cgroup_subsys_state *css, struct cftype *cft)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
	u64 val;

	switch (cft->private) {
	case RES_LIMIT:
		if (memcg == root_mem_cgroup)
			val = PAGE_COUNTER_MAX;
		else
			val = memcg->tcp_mem.memory_allocated.limit;
		val *= PAGE_SIZE;
		break;
	case RES_USAGE:
		if (memcg == root_mem_cgroup)
			val = atomic_long_read(&tcp_memory_allocated);
		else
			val = page_counter_read(&memcg->tcp_mem.memory_allocated);
		val *= PAGE_SIZE;
		break;
	case RES_FAILCNT:
		if (memcg == root_mem_cgroup)
			return 0;
		val = memcg->tcp_mem.memory_allocated.failcnt;
		break;
	case RES_MAX_USAGE:
		if (memcg == root_mem_cgroup)
			return 0;
		val = memcg->tcp_mem.memory_allocated.watermark;
		val *= PAGE_SIZE;
		break;
	default:
		BUG();
	}
	return val;
}

static ssize_t tcp_cgroup_reset(struct kernfs_open_file *of,
				char *buf, size_t nbytes, loff_t off)
{
	struct mem_cgroup *memcg;

	memcg = mem_cgroup_from_css(of_css(of));
	if (memcg == root_mem_cgroup)
		return nbytes;

	switch (of_cft(of)->private) {
	case RES_MAX_USAGE:
		page_counter_reset_watermark(&memcg->tcp_mem.memory_allocated);
		break;
	case RES_FAILCNT:
		memcg->tcp_mem.memory_allocated.failcnt = 0;
		break;
	}

	return nbytes;
}

static struct cftype tcp_files[] = {
	{
		.name = "kmem.tcp.limit_in_bytes",
		.write = tcp_cgroup_write,
		.read_u64 = tcp_cgroup_read,
		.private = RES_LIMIT,
	},
	{
		.name = "kmem.tcp.usage_in_bytes",
		.read_u64 = tcp_cgroup_read,
		.private = RES_USAGE,
	},
	{
		.name = "kmem.tcp.failcnt",
		.private = RES_FAILCNT,
		.write = tcp_cgroup_reset,
		.read_u64 = tcp_cgroup_read,
	},
	{
		.name = "kmem.tcp.max_usage_in_bytes",
		.private = RES_MAX_USAGE,
		.write = tcp_cgroup_reset,
		.read_u64 = tcp_cgroup_read,
	},
	{ }	/* terminate */
};

static int __init tcp_memcontrol_init(void)
{
	WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys, tcp_files));
	return 0;
}
__initcall(tcp_memcontrol_init);