cg: restore special cpuset props only in cgs criu creates

Previously we were trying to copy the root cg properties recursively to attempt
to correct invalid restores. However, based on some ML discussion, we should
only restore exactly what was dumped. Users need to set up their cg heirarchies
correctly (that is, they should not set up any options in the parent that would
conflict with what was dumped) in order to restore successfully.
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cgroup.c

@@ -868,112 +868,6 @@ static const char *special_cpuset_props[] = {
 	NULL,
 };
 
-static int find_value(const char *controller, const char *path, const char *prop,
-			char *value, char *prefix, char *missing_path)
-{
-	char fpath[PATH_MAX], my_path[PATH_MAX];
-	char *pos;
-	int ret, cg;
-
-	cg = get_service_fd(CGROUP_YARD);
-	strncpy(my_path, path, PATH_MAX);
-
-	while (1) {
-		FILE *f;
-
-		pos = strrchr(my_path, '/');
-		if (pos) {
-			*pos = 0;
-			snprintf(prefix, PATH_MAX, "%s/%s", controller, my_path);
-		} else {
-			snprintf(fpath, PATH_MAX, "%s", controller);
-		}
-		snprintf(fpath, PATH_MAX, "%s/%s", prefix, prop);
-
-		f = fopenat(cg, fpath, "r");
-		if (!f)
-			return -1;
-
-		ret = fscanf(f, "%1024s", value);
-		fclose(f);
-
-		if (ret > 0) {
-			strcpy(missing_path, path + (pos - my_path));
-			return 0;
-		} else if (!pos) {
-			pr_err("didn't find a value to propogate in the root!\n");
-			return -1;
-		}
-	}
-
-	return -1;
-}
-
-static int copy_recursive(const char *prefix, char *path, const char *prop, const char *value)
-{
-	char fpath[PATH_MAX];
-	char *pos;
-	int ret, out, cg;
-
-	cg = get_service_fd(CGROUP_YARD);
-
-	/* skip the first / */
-	pos = path + 1;
-	while (1) {
-		pos = strchr(pos, '/');
-
-		if (pos)
-			*pos = 0;
-		snprintf(fpath, PATH_MAX, "%s/%s/%s", prefix, path, prop);
-		if (pos) {
-			*pos = '/';
-			pos++;
-		}
-
-		out = openat(cg, fpath, O_RDWR);
-		if (out < 0) {
-			pr_perror("couldn't open cg prop at %s\n", fpath);
-			return -1;
-		}
-
-		ret = write(out, value, strlen(value));
-		close(out);
-
-		if (ret < 0) {
-			pr_perror("copying property %s to %s failed\n", prop, fpath);
-			return -1;
-		}
-
-		if (!pos)
-			break;
-	}
-
-	return 0;
-}
-
-static int copy_special_cg_props(const char *controller, char *path)
-{
-	pr_info("copying special cg props for %s\n", controller);
-
-	if (strstr(controller, "cpuset")) {
-		int i;
-
-		for (i = 0; special_cpuset_props[i]; i++) {
-			char buf[1024], prefix[PATH_MAX], missing_path[PATH_MAX];
-			const char *prop = special_cpuset_props[i];
-			if (find_value(controller, path, prop, buf, prefix, missing_path) < 0)
-				return -1;
-
-			if (copy_recursive(prefix, missing_path, prop, buf) < 0) {
-				pr_err("copying prop %s failed\n", prop);
-				return -1;
-			}
-		}
-	}
-
-	return 0;
-}
-
 static int move_in_cgroup(CgSetEntry *se)
 {
 	int cg, i;
@@ -1001,11 +895,6 @@ static int move_in_cgroup(CgSetEntry *se)
 
 		aux_off = ctrl_dir_and_opt(ctrl, aux, sizeof(aux), NULL, 0);
 
-		if (copy_special_cg_props(aux, ce->path) < 0) {
-			pr_perror("Couldn't copy special cgroup properties\n");
-			return -1;
-		}
-
 		snprintf(aux + aux_off, sizeof(aux) - aux_off, "/%s/tasks", ce->path);
 		pr_debug("  `-> %s\n", aux);
 		err = fd = openat(cg, aux, O_WRONLY);
@@ -1149,9 +1038,29 @@ int prepare_cgroup_properties(void)
 	return 0;
 }
 
-static int prepare_cgroup_dirs(char *paux, size_t off, CgroupDirEntry **ents, size_t n_ents)
+static int restore_special_cpuset_props(char *paux, size_t off, CgroupDirEntry *e)
+{
+	int i, j;
+
+	for (i = 0; special_cpuset_props[i]; i++) {
+		const char *name = special_cpuset_props[i];
+
+		for (j = 0; j < e->n_properties; j++) {
+			CgroupPropEntry *prop = e->properties[j];
+
+			if (strcmp(name, prop->name) == 0)
+				if (restore_cgroup_prop(prop, paux, off) < 0)
+					return -1;
+		}
+	}
+
+	return 0;
+}
+
+static int prepare_cgroup_dirs(char **controllers, int n_controllers, char *paux, size_t off,
+				CgroupDirEntry **ents, size_t n_ents)
 {
-	size_t i;
+	size_t i, j;
 	CgroupDirEntry *e;
 	int cg = get_service_fd(CGROUP_YARD);
 
@@ -1178,6 +1087,15 @@ static int prepare_cgroup_dirs(char *paux, size_t off, CgroupDirEntry **ents, si
 				return -1;
 			}
 			pr_info("Created dir %s\n", paux);
+
+			for (j = 0; j < n_controllers; j++) {
+				if (strcmp(controllers[j], "cpuset") == 0) {
+					if (restore_special_cpuset_props(paux, off2, e) < 0) {
+						pr_err("Restoring special cpuset props failed!\n");
+						return -1;
+					}
+				}
+			}
 		} else {
 			if (e->n_properties > 0) {
 				xfree(e->properties);
@@ -1187,7 +1105,8 @@ static int prepare_cgroup_dirs(char *paux, size_t off, CgroupDirEntry **ents, si
 			pr_info("Determined dir %s already existed\n", paux);
 		}
 
-		if (prepare_cgroup_dirs(paux, off2, e->children, e->n_children) < 0)
+		if (prepare_cgroup_dirs(controllers, n_controllers, paux, off2,
+				e->children, e->n_children) < 0)
 			return -1;
 	}
 
@@ -1286,7 +1205,8 @@ static int prepare_cgroup_sfd(CgroupEntry *ce)
 		yard = paux + strlen(cg_yard) + 1;
 		yard_off = ctl_off - (strlen(cg_yard) + 1);
 		if (opts.manage_cgroups &&
-		    prepare_cgroup_dirs(yard, yard_off, ctrl->dirs, ctrl->n_dirs))
+		    prepare_cgroup_dirs(ctrl->cnames, ctrl->n_cnames, yard, yard_off,
+				ctrl->dirs, ctrl->n_dirs))
 			goto err;
 
 	}