/
ext4-data-loss.c
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/
ext4-data-loss.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#define NFILES 64
/* fdatasync is default on Linux */
#define SYNC(a) fdatasync(a)
static void prepare_files(int nfiles);
static void rewrite_file(int fd);
static void
rewrite_file(int fd)
{
int i;
char data[1024];
/* 1kB of zeroes */
memset(data, 0, 1024);
/* write 16MB of data (zeroes) to the file */
for (i = 0; i < 16 * 1024; i++)
{
if (write(fd, data, 1024) != 1024)
{
printf("write failed");
exit(6);
}
}
}
static void
prepare_files(int nfiles)
{
int i, j;
char fname[1024];
for (i = 0; i < nfiles; i++)
{
int fd;
sprintf(fname, "%d", i);
if ((fd = open(fname, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR)) == -1)
{
printf("open failed");
exit(7);
}
rewrite_file(fd);
/* fdatasync is default on linux */
if (SYNC(fd) != 0)
{
printf("sync failed");
exit(8);
}
if (close(fd) != 0)
{
printf("close failed");
exit(9);
}
}
}
void main()
{
int i, f;
prepare_files(NFILES);
f = NFILES;
/* now create a new file by renaming the oldest one, rewrite and sync */
while (1)
{
int fd;
char fname_old[1024];
char fname_new[1024];
sprintf(fname_old, "%d", f-NFILES);
sprintf(fname_new, "%d", f);
if (rename(fname_old, fname_new) != 0)
{
printf("rename failed");
exit(1);
}
if ((fd = open(fname_new, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR)) == -1)
{
printf("open failed");
exit(2);
}
rewrite_file(fd);
/* fdatasync is default on linux */
if (SYNC(fd) != 0)
{
printf("sync failed");
exit(3);
}
if (close(fd) != 0)
{
printf("close failed");
exit(4);
}
printf("file %s\n", fname_new);
/* sleep for 1 second */
sleep(1);
/* next file */
f += 1;
}
}