Add fsfreeze(8)

Makefile

@@ -31,6 +31,7 @@ SRC = \
 	eject.c             \
 	fallocate.c         \
 	free.c              \
+	fsfreeze.c          \
 	getty.c             \
 	halt.c              \
 	hwclock.c           \

fsfreeze.c

@@ -0,0 +1,51 @@
+/* See LICENSE file for copyright and license details. */
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include "util.h"
+
+#define FIFREEZE	_IOWR('X', 119, int	/* Freeze */
+#define FITHAW		_IOWR('X', 120, int)	/* Thaw */
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [-f] [-u] mountpoint\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int fflag = 0;
+	int uflag = 0;
+	long p = 1;
+	int fd;
+
+	ARGBEGIN {
+	case 'f':
+		fflag = 1;
+		break;
+	case 'u':
+		uflag = 1;
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (argc != 1)
+		usage();
+
+	if ((fflag ^ uflag) == 0)
+		usage();
+
+	fd = open(argv[0], O_RDONLY);
+	if (fd < 0)
+		eprintf("open: %s:", argv[0]);
+	ioctl(fd, fflag == 1 ? FIFREEZE : FITHAW, &p);
+	close(fd);
+	return EXIT_SUCCESS;
+}