/*

 * cg_map.c	cgroup v2 cache

 *

 *		This program is free software; you can redistribute it and/or

 *		modify it under the terms of the GNU General Public License

 *		as published by the Free Software Foundation; either version

 *		2 of the License, or (at your option) any later version.

 *

 * Authors:	Dmitry Yakunin <zeil@yandex-team.ru>

 */

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <stdbool.h>

#include <linux/types.h>

#include <linux/limits.h>

#include <ftw.h>

#include "cg_map.h"

#include "list.h"

#include "utils.h"

struct cg_cache {

	struct hlist_node id_hash;

	__u64	id;

	char	path[];

};

#define IDMAP_SIZE	1024

static struct hlist_head id_head[IDMAP_SIZE];

static struct cg_cache *cg_get_by_id(__u64 id)

{

	unsigned int h = id & (IDMAP_SIZE - 1);

	struct hlist_node *n;

	hlist_for_each(n, &id_head[h]) {

		struct cg_cache *cg;

		cg = container_of(n, struct cg_cache, id_hash);

		if (cg->id == id)

			return cg;

	}

	return NULL;

}

static struct cg_cache *cg_entry_create(__u64 id, const char *path)

{

	unsigned int h = id & (IDMAP_SIZE - 1);

	struct cg_cache *cg;

	cg = malloc(sizeof(*cg) + strlen(path) + 1);

	if (!cg) {

		fprintf(stderr,

			"Failed to allocate memory for cgroup2 cache entry");

		return NULL;

	}

	cg->id = id;

	strcpy(cg->path, path);

	hlist_add_head(&cg->id_hash, &id_head[h]);

	return cg;

}

static int mntlen;

static int nftw_fn(const char *fpath, const struct stat *sb,

		   int typeflag, struct FTW *ftw)

{

	const char *path;

	__u64 id;

	if (typeflag != FTW_D)

		return 0;

	id = get_cgroup2_id(fpath);

	if (!id)

		return -1;

	path = fpath + mntlen;

	if (*path == '\0')

		/* root cgroup */

		path = "/";

	if (!cg_entry_create(id, path))

		return -1;

	return 0;

}

static void cg_init_map(void)

{

	char *mnt;

	mnt = find_cgroup2_mount(false);

	if (!mnt)

		return;

	mntlen = strlen(mnt);

	(void) nftw(mnt, nftw_fn, 1024, FTW_MOUNT);

	free(mnt);

}

const char *cg_id_to_path(__u64 id)

{

	static int initialized;

	static char buf[64];

	const struct cg_cache *cg;

	char *path;

	if (!initialized) {

		cg_init_map();

		initialized = 1;

	}

	cg = cg_get_by_id(id);

	if (cg)

		return cg->path;

	path = get_cgroup2_path(id, false);

	if (path) {

		cg = cg_entry_create(id, path);

		free(path);

		if (cg)

			return cg->path;

	}

	snprintf(buf, sizeof(buf), "unreachable:%llx", id);

	return buf;

}