Restore a thread to a correct v1 cgroup

criu/cgroup.c

@@ -427,10 +427,11 @@ static int dump_cg_props_array(const char *fpath, struct cgroup_dir *ncd, const
 		}
 
 		/*
-		 * Set the is_threaded flag if cgroup.type's value is threaded,
-		 * ignore all other values.
+		 * Set the is_threaded flag if cgroup.type's value is threaded
+		 * or it is a cgroup v1 (it has a 'tasks' property).
+		 * Ignore all other values.
 		 */
-		if (!strcmp("cgroup.type", prop->name) && !strcmp("threaded", prop->value))
+		if ((!strcmp("cgroup.type", prop->name) && !strcmp("threaded", prop->value)) || !strcmp("tasks", prop->name))
 			controller->is_threaded = true;
 
 		pr_info("Dumping value %s from %s/%s\n", prop->value, fpath, prop->name);
@@ -1922,7 +1923,7 @@ static int prepare_cgroup_sfd(CgroupEntry *ce)
 			if (ctrl->cnames[0][0] == 0)
 				fstype = "cgroup2";
 
-			pr_debug("\tMaking controller dir %s (%s)\n", paux, opt);
+			pr_debug("\tMaking controller dir %s (%s), type %s\n", paux, opt, fstype);
 			if (mkdir(paux, 0700)) {
 				pr_perror("\tCan't make controller dir %s", paux);
 				return -1;
@@ -1985,6 +1986,7 @@ static int cgroupd(int sk)
 			CgMemberEntry *ce = cg_set_entry->ctls[i];
 			char aux[PATH_MAX];
 			CgControllerEntry *ctrl = NULL;
+			const char *format;
 
 			for (j = 0; j < n_controllers; j++) {
 				CgControllerEntry *cur = controllers[j];
@@ -2008,7 +2010,8 @@ static int cgroupd(int sk)
 				continue;
 
 			aux_off = ctrl_dir_and_opt(ctrl, aux, sizeof(aux), NULL, 0);
-			snprintf(aux + aux_off, sizeof(aux) - aux_off, "/%s/cgroup.threads", ce->path);
+			format = ctrl->cnames[0][0] ? "/%s/tasks" : "/%s/cgroup.threads";
+			snprintf(aux + aux_off, sizeof(aux) - aux_off, format, ce->path);
 
 			/*
 			 * Cgroupd runs outside of the namespaces so we don't

test/zdtm/static/Makefile

@@ -402,6 +402,7 @@ TST_DIR		=				\
 		cgroup_ignore			\
 		cgroup_stray			\
 		cgroup_yard			\
+		cgroup_threads			\
 		unlink_fstat04			\
 		unlink_fstat041			\
 		mntns_remap			\
@@ -684,6 +685,8 @@ s390x_gs_threads:	LDFLAGS += -pthread
 
 thread_different_uid_gid:	LDLIBS += -pthread -lcap
 
+cgroup_threads:		LDFLAGS += -pthread
+
 bpf_hash:		LDLIBS += -lbpf
 bpf_array:		LDLIBS += -lbpf
 

test/zdtm/static/cgroup_threads.c

@@ -0,0 +1,155 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/mount.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check that cgroup layout of threads is preserved";
+const char *test_author	= "Michał Cłapiński <[email protected]>";
+
+char *dirname;
+TEST_OPTION(dirname, string, "cgroup directory name", 1);
+static const char *cgname = "zdtmtst";
+#define SUBNAME	 "subcg_threads"
+#define SUBNAME2 SUBNAME "/subsubcg"
+
+static int cg_move(char *name)
+{
+	int cgfd, l;
+	char paux[256];
+
+	sprintf(paux, "%s/%s", dirname, name);
+	mkdir(paux, 0600);
+
+	sprintf(paux, "%s/%s/tasks", dirname, name);
+
+	cgfd = open(paux, O_WRONLY);
+	if (cgfd < 0) {
+		pr_perror("Can't open tasks");
+		return -1;
+	}
+
+	l = write(cgfd, "0", 2);
+	close(cgfd);
+
+	if (l < 0) {
+		pr_perror("Can't move self to subcg");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int cg_check(char *name)
+{
+	int found = 0;
+	FILE *cgf;
+	char paux[256], aux[128];
+
+	cgf = fopen("/proc/thread-self/cgroup", "r");
+	if (cgf == NULL)
+		return -1;
+
+	sprintf(aux, "name=%s:/%s", cgname, name);
+	while (fgets(paux, sizeof(paux), cgf)) {
+		char *s;
+
+		s = strchr(paux, ':') + 1;
+		s[strlen(s) - 1] = '\0';
+		test_msg("CMP [%s] vs [%s]\n", s, aux);
+		if (!strcmp(s, aux)) {
+			found = 1;
+			break;
+		}
+	}
+
+	fclose(cgf);
+
+	return found ? 0 : -1;
+}
+
+int p1[2], pr[2];
+
+void *child(void *args)
+{
+	int status = cg_move(SUBNAME2);
+	write(p1[1], &status, sizeof(status));
+
+	if (status == 0) {
+		read(pr[0], &status, sizeof(status));
+
+		status = cg_check(SUBNAME2);
+		write(p1[1], &status, sizeof(status));
+	}
+
+	pthread_exit(0);
+}
+
+int main(int argc, char **argv)
+{
+	char aux[64];
+	int status;
+	pthread_t thread;
+
+	test_init(argc, argv);
+
+	/*
+	 * Pipe to talk to the kid.
+	 * First, it reports that it's ready (int),
+	 * then it reports the restore status (int).
+	 */
+
+	pipe(p1);
+
+	/* "Restore happened" pipe */
+	pipe(pr);
+
+	if (mkdir(dirname, 0700) < 0) {
+		pr_perror("Can't make dir");
+		goto out;
+	}
+
+	sprintf(aux, "none,name=%s", cgname);
+	if (mount("none", dirname, "cgroup", 0, aux)) {
+		pr_perror("Can't mount cgroups");
+		goto out_rd;
+	}
+
+	if (cg_move(SUBNAME))
+		goto out_rs;
+
+	pthread_create(&thread, NULL, child, NULL);
+
+	status = -1;
+	read(p1[0], &status, sizeof(status));
+	if (status != 0) {
+		pr_perror("Error moving into cgroups");
+		close(pr[0]);
+		goto out_rs;
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	close(pr[1]);
+
+	status = -1;
+	read(p1[0], &status, sizeof(status));
+	if (status != 0) {
+		fail("child cg changed");
+		goto out_rs;
+	}
+
+	pass();
+
+out_rs:
+	umount(dirname);
+out_rd:
+	rmdir(dirname);
+out:
+	return 0;
+}

test/zdtm/static/cgroup_threads.desc

@@ -0,0 +1 @@
+{'flavor': 'h', 'flags': 'suid', 'opts': '--manage-cgroups'}

test/zdtm/static/cgroup_threads.hook

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+[ "$1" == "--clean" -o "$1" == "--pre-restore" ] || exit 0
+
+set -e
+
+tname=$(mktemp -d cgclean.XXXXXX)
+trap 'rmdir "${tname}"' EXIT
+
+mount -t cgroup none $tname -o "none,name=zdtmtst"
+trap 'umount "${tname}"; rmdir "${tname}"' EXIT
+
+echo "Cleaning $tname"
+
+rmdir "$tname/subcg_threads/subsubcg/" || true
+rmdir "$tname/subcg_threads/" || true
+
+echo "Left there is:"
+ls "$tname"