zdtm: Check that files from alien mnt ns are handled (v2)

Check that files opened before switching to new mount namespace
remain in it after restore. Right now this is not so :( Andrey is
fixing the issue.

Christopher, can you check whether the ns_child's call to system()
works in your minimal set-ups (it launches cat and awk). If not,
then I should rewrite this routine in pure C.

The first version was written by Pavel (xemul@).

v2: don't use test_init_ns
    don't call awk and cat
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm.sh

@@ -174,6 +174,7 @@ static/netns
 static/cgroup00
 static/cgroup01
 ns/static/clean_mntns
+ns/static/mntns_open
 "
 
 TEST_CR_KERNEL="
@@ -207,6 +208,7 @@ cgroup00
 cgroup01
 clean_mntns
 deleted_dev
+mntns_open
 "
 
 source $(readlink -f `dirname $0`/env.sh) || exit 1
@@ -389,7 +391,7 @@ start_test()
 			mkdir -p dump
 			ZDTM_ROOT=`mktemp -d /tmp/criu-root.XXXXXX`
 			ZDTM_ROOT=`readlink -f $ZDTM_ROOT`
-			mount --bind . $ZDTM_ROOT || return 1
+			mount --make-private --bind . $ZDTM_ROOT || return 1
 		fi
 		construct_root $ZDTM_ROOT $tdir/$tname || return 1
 		export ZDTM_NEWNS=1

test/zdtm/live/static/Makefile

@@ -164,6 +164,7 @@ TST_DIR		=				\
 		cgroup00			\
 		rmdir_open			\
 		cgroup01			\
+		mntns_open			\
 
 TST_DIR_FILE	=				\
 		chroot				\

test/zdtm/live/static/mntns_open.c

+#define _GNU_SOURCE
+#include <stdbool.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sched.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+#include <limits.h>
+
+#include "zdtmtst.h"
+
+#ifndef CLONE_NEWNS
+#define CLONE_NEWNS     0x00020000
+#endif
+
+const char *test_doc	= "Check that mnt_id is repsected";
+const char *test_author	= "Pavel Emelianov <xemul@parallels.com>";
+
+#define MPTS_FILE	"F"
+char *dirname;
+TEST_OPTION(dirname, string, "directory name", 1);
+char fpath[PATH_MAX];
+
+#define NS_STACK_SIZE	4096
+/* All arguments should be above stack, because it grows down */
+struct ns_exec_args {
+	char stack[NS_STACK_SIZE];
+	char stack_ptr[0];
+	int fd;
+};
+
+#define AWK_OK		13
+#define AWK_FAIL	42
+
+static int get_mntid(int fd)
+{
+	char str[256];
+	int mnt_id = -1;
+	FILE *f;
+
+	snprintf(str, sizeof(str), "/proc/self/fdinfo/%d", fd);
+	f = fopen(str, "r");
+	if (!f) {
+		err("Can't open %s to parse", str);
+		return -1;
+	}
+	while (fgets(str, sizeof(str), f)) {
+		if (sscanf(str, "mnt_id: %d", &mnt_id) == 1)
+			break;
+	}
+
+	fclose(f);
+	return mnt_id;
+}
+
+int ns_child(void *_arg)
+{
+	struct ns_exec_args *args = _arg;
+	int fd2;
+	int id1, id2;
+
+	fd2 = open(fpath, O_RDWR);
+	test_waitsig();
+
+	id1 = get_mntid(args->fd);
+	id2 = get_mntid(fd2);
+
+	test_msg("%d %d", id1, id2);
+
+	if (id1 <0 || id2 < 0)
+		exit(1);
+	if (id1 > 0 && id1 != id2)
+		exit(AWK_OK);
+	else
+		exit(AWK_FAIL);
+}
+
+int main(int argc, char **argv)
+{
+	struct ns_exec_args args;
+	pid_t pid = -1;
+
+	test_init(argc, argv);
+
+	snprintf(fpath, sizeof(fpath), "%s/%s", dirname, MPTS_FILE);
+	if (mkdir(dirname, 0600) < 0) {
+		fail("Can't make zdtm_sys");
+		return 1;
+	}
+
+	if (getenv("ZDTM_NOSUBNS") == NULL) {
+		args.fd = open(fpath, O_CREAT | O_RDWR, 0600);
+		if (args.fd < 0) {
+			fail("Can't open file");
+			return 1;
+		}
+
+		pid = clone(ns_child, args.stack_ptr, CLONE_NEWNS | SIGCHLD, &args);
+		if (pid < 0) {
+			err("Unable to fork child");
+			return 1;
+		}
+
+		close(args.fd);
+	}
+
+	test_daemon();
+	test_waitsig();
+
+
+	if (pid > 0) {
+		kill(pid, SIGTERM);
+		int status = 1;
+		wait(&status);
+		if (WIFEXITED(status)) {
+			if (WEXITSTATUS(status) == AWK_OK)
+				pass();
+			else if (WEXITSTATUS(status) == AWK_FAIL)
+				fail("Mount ID not restored");
+			else
+				fail("Failed to check mount IDs (%d)", WEXITSTATUS(status));
+		} else
+			fail("Test died");
+	}
+
+	unlink(fpath);
+	rmdir(dirname);
+	return 0;
+}