1 files changed, 134 insertions, 0 deletions
diff --git a/lib/cg_map.c b/lib/cg_map.c
new file mode 100644
index 0000000..39f244d
--- /dev/null
+++ b/lib/cg_map.c
@@ -0,0 +1,134 @@
+/*
+ * 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;
+}