zdtm: Add ztatic/mnt_ext_file_bind_auto test

The test creates a file bindmount in criu mntns and binds it into test
mntns, this external file bindmount is autodetected and restored via
"--external mnt[]" criu option.

Note: In previous patch we fix the problem on this code path where file
bindmount restore fails as there is excess "/" in source path.

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>

test/zdtm/static/Makefile

@@ -381,6 +381,7 @@ TST_FILE	=				\
 		sk-unix-listen02		\
 		sk-unix-listen03		\
 		sk-unix-listen04		\
+		mnt_ext_file_bind_auto		\
 
 TST_DIR		=				\
 		cwd00				\

test/zdtm/static/mnt_ext_file_bind_auto.c

@@ -0,0 +1,104 @@
+#include <sys/mount.h>
+#include <linux/limits.h>
+#include <sys/stat.h>
+#include <sched.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc = "Check if external file mount works";
+const char *test_author = "Pavel Tikhomirov <ptikhomirov@virtuozzo.com>";
+
+char *filename = "mnt_ext_file_bind_auto_bind_auto.file";
+TEST_OPTION(filename, string, "file name", 1);
+
+char *source = "mnt_ext_file_bind_auto_bind_auto.source";
+
+int create_file(const char *path)
+{
+	int fd;
+
+	fd = open(path, O_CREAT | O_RDWR, 0644);
+	if (fd < 0) {
+		pr_perror("open");
+		return -1;
+	}
+
+	close(fd);
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	char *zdtm_newns = getenv("ZDTM_NEWNS");
+	char *tmp = "/tmp/zdtm_ext_file_bind_auto.tmp";
+	char *sourcefile = "/tmp/zdtm_ext_file_bind_auto.file";
+	char *root, tmpfile[PATH_MAX], testfile[PATH_MAX];
+
+	root = getenv("ZDTM_ROOT");
+	if (root == NULL) {
+		pr_perror("root");
+		return 1;
+	}
+
+	if (!zdtm_newns) {
+		pr_perror("ZDTM_NEWNS is not set");
+		return 1;
+	} else if (strcmp(zdtm_newns, "1")) {
+		goto test;
+	}
+
+	/* Prepare file bindmount in criu root (source for external file bindmount) */
+        mkdir(tmp, 0755);
+        if (mount(source, tmp, "tmpfs", 0, NULL)) {
+                pr_perror("mount tmpfs");
+                return 1;
+        }
+        if (mount(NULL, tmp, NULL, MS_PRIVATE, NULL)) {
+                pr_perror("make private");
+                return 1;
+        }
+
+	sprintf(tmpfile, "%s/%s", tmp, filename);
+	if (create_file(tmpfile))
+		return 1;
+
+	if (create_file(sourcefile))
+		return 1;
+
+	if (mount(tmpfile, sourcefile, NULL, MS_BIND, NULL)) {
+		pr_perror("bind");
+		return 1;
+	}
+
+	umount2(tmp, MNT_DETACH);
+
+	/* Prepare file in test root (mount point for external file bindmount) */
+	sprintf(testfile, "%s/%s", root, filename);
+	if (create_file(testfile))
+		return 1;
+
+	/*
+	 * Create temporary mntns, next mounts will not show up in criu mntns
+	 * and will be inherited into test mntns
+	 */
+	if (unshare(CLONE_NEWNS)) {
+		pr_perror("unshare");
+		return 1;
+	}
+
+	if (mount(sourcefile, testfile, NULL, MS_BIND, NULL)) {
+                pr_perror("bind");
+                return 1;
+        }
+test:
+	test_init(argc, argv);
+
+	test_daemon();
+	test_waitsig();
+
+	pass();
+	return 0;
+}

test/zdtm/static/mnt_ext_file_bind_auto.desc

@@ -0,0 +1,4 @@
+{   'opts': '--external mnt[]',
+    'feature': 'mnt_id',
+    'flavor': 'ns uns',
+    'flags': 'suid'}