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

#define PAGE_SIZE 4096

int test(char* file)
{
    char* buf = NULL;
    int ret = 0;
    int i = 0;
    posix_memalign((void**)(&buf), PAGE_SIZE, PAGE_SIZE);
    memset(buf, 0, PAGE_SIZE);
    for (i = 0 ; i < PAGE_SIZE ; ++i) buf[i] = i;
    int fd = open(file, O_WRONLY|O_CREAT|O_DIRECT|O_SYNC);
    if (fd == -1)
    {
        fprintf(stderr, "%s: %s\n", file, strerror(errno));
        exit(1);
    }
    struct stat st;
    ret = fstat(fd, &st);
    if (ret != 0)
    {
        fprintf(stderr, "%s: %s\n", file, strerror(errno));
        exit(1);
    }
    int offset = st.st_size;
    ret = pwrite(fd, buf, PAGE_SIZE, offset);
    if (ret != PAGE_SIZE)
    {
        fprintf(stderr, "write fail: ret %d %s\n", ret, strerror(errno));
    }
    close(fd);
    return 0;
}

int main(int argc, char ** argv)
{
    int ret = 0;
    char file[1024] = {};
    if (argc != 2)
    {
        fprintf(stderr, "usage: %s path-to-write\n", argv[0]);
        exit(2);
    }
    snprintf(file, sizeof(file), "%s_%d", argv[1], 0);
    test(file);
    return 0;
}