zdtm/inotify: add a test that no unexpected events appear after c/r

Just create two inotify watches on a testfile, and do nothing except
c/r, it is expected that there is no events in queue after these.

before "inotify: cleanup auxiliary events from queue":

[root@snorch criu]# ./test/zdtm.py run -t zdtm/static/inotify04
=== Run 1/1 ================ zdtm/static/inotify04
======================== Run zdtm/static/inotify04 in h ========================
 DEP       inotify04.d
 CC        inotify04.o
 LINK      inotify04
Start test
./inotify04 --pidfile=inotify04.pid --outfile=inotify04.out --dirname=inotify04.test
Run criu dump
Run criu restore
Send the 15 signal to  60
Wait for zdtm/static/inotify04(60) to die for 0.100000
=============== Test zdtm/static/inotify04 FAIL at result check ================
Test output: ================================
18:37:14.279:    60: Event       0x10
18:37:14.280:    60: Event       0x20
18:37:14.280:    60: Event       0x10
18:37:14.280:    60: Read 3 events
18:37:14.280:    60: FAIL: inotify04.c:105: Found 3 unexpected inotify events (errno = 11 (Resource temporarily unavailable))

<<< ================================

v2: make two inotifies on the same file

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

zdtm: inotify04 add another inotify on the same file

test/zdtm/static/Makefile

@@ -311,6 +311,7 @@ TST_DIR		=				\
 		inotify00			\
 		inotify01			\
 		inotify02			\
+		inotify04			\
 		cgroup00			\
 		rmdir_open			\
 		cgroup01			\

test/zdtm/static/inotify04.c

@@ -0,0 +1,124 @@
+#include <unistd.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/inotify.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check inotify does not have trash in queue after c/r";
+const char *test_author	= "Pavel Tikhomirov <ptikhomirov@virtuozzo.com>";
+
+char *dirname;
+TEST_OPTION(dirname, string, "directory name", 1);
+
+#define TEST_FILE	"inotify-testfile"
+
+#define BUFF_SIZE ((sizeof(struct inotify_event) + PATH_MAX))
+
+static int inotify_read_events(int inotify_fd, unsigned int *n)
+{
+	struct inotify_event *event;
+	char buf[BUFF_SIZE * 8];
+	int ret, off;
+
+	*n = 0;
+
+	while (1) {
+		ret = read(inotify_fd, buf, sizeof(buf));
+		if (ret < 0) {
+			if (errno != EAGAIN) {
+				pr_perror("Can't read inotify queue");
+				return -1;
+			} else {
+				ret = 0;
+				break;
+			}
+		} else if (ret == 0)
+			break;
+
+		for (off = 0; off < ret; (*n)++, off += sizeof(*event) + event->len) {
+			event = (void *)(buf + off);
+			test_msg("Event %#10x\n", event->mask);
+		}
+	}
+
+	test_msg("Read %u events\n", *n);
+	return ret;
+}
+
+int main (int argc, char *argv[])
+{
+	unsigned int mask = IN_ALL_EVENTS;
+	char test_file_path[PATH_MAX];
+	int fd, ifd, ifd2, ret;
+	unsigned int n;
+
+	test_init(argc, argv);
+
+	if (mkdir(dirname, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH)) {
+		pr_perror("Can't create directory %s", dirname);
+		return 1;
+	}
+
+	snprintf(test_file_path, sizeof(test_file_path), "%s/%s", dirname, TEST_FILE);
+
+	fd = open(test_file_path, O_CREAT, 0644);
+	if (fd < 0) {
+		pr_perror("Failed to create %s", test_file_path);
+		return 1;
+	}
+	close(fd);
+
+	ifd = inotify_init1(IN_NONBLOCK);
+	if (ifd < 0) {
+		pr_perror("Failed inotify_init");
+		return 1;
+	}
+
+	ifd2 = inotify_init1(IN_NONBLOCK);
+	if (ifd2 < 0) {
+		pr_perror("Failed inotify_init");
+		return 1;
+	}
+
+	if (inotify_add_watch(ifd, test_file_path, mask) < 0) {
+		pr_perror("Failed inotify_add_watch");
+		return 1;
+	}
+
+	if (inotify_add_watch(ifd2, test_file_path, mask) < 0) {
+		pr_perror("Failed inotify_add_watch");
+		return 1;
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	ret = inotify_read_events(ifd, &n);
+	if (ret < 0) {
+		fail("Failed to read inotify events");
+		return 1;
+	} else if (n != 0) {
+		fail("Found %d unexpected inotify events", n);
+		return 1;
+	}
+
+	ret = inotify_read_events(ifd, &n);
+	if (ret < 0) {
+		fail("Failed to read inotify events");
+		return 1;
+	} else if (n != 0) {
+		fail("Found %d unexpected inotify events", n);
+		return 1;
+	}
+
+	close(ifd);
+	close(ifd2);
+	unlink(test_file_path);
+	pass();
+
+	return 0;
+}