FIGETFROZEN in action

gistfile1.txt

root@localhost:/mnt# gcc is_frozen.c -o is_frozen
root@localhost:/mnt# ./is_frozen /
frozen status: 0
root@localhost:/mnt# fsfreeze --freeze /
root@localhost:/mnt# ./is_frozen /
frozen status: 4
root@localhost:/mnt# fsfreeze --unfreeze /
root@localhost:/mnt# ./is_frozen /
frozen status: 0

is_frozen.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/fs.h>

int
main(int argc, char* argv[])
{
        int fd;
        int frozen;

        if (argc != 2)
        {
                printf("usage: ./is_frozen <mountpoint>\n");
                return -1;
        }

        fd = open(argv[1], O_RDONLY);
        if (fd < 0)
                return -errno;

        if (ioctl(fd, FIGETFROZEN, &frozen) < 0)
                return -errno;

        printf("frozen status: %d\n", frozen);

        close(fd);

        return 0;
}