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#define _GNU_SOURCE
#include <stdlib.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <linux/btrfs.h>
#include <linux/magic.h>
#include <linux/types.h>
#include <sys/ioctl.h>
#include <sys/statfs.h>
/*
* Constants defined in BTRFS' experimental shutdown support
* starting from Linux 6.19.
*/
#ifndef BTRFS_SHUTDOWN_FLAGS_DEFAULT
#define BTRFS_SHUTDOWN_FLAGS_DEFAULT 0x0
#endif
#ifndef BTRFS_IOC_SHUTDOWN
#define BTRFS_IOC_SHUTDOWN _IOR('X', 125, __u32)
#endif
int main(int argc, char *argv[])
{
int fd;
__u32 flags;
struct statfs info;
if (argc < 2) {
fprintf(stderr, "usage: %s <mount point>\n", argv[0]);
exit(EXIT_FAILURE);
}
if (statfs(argv[1], &info) == 0) {
/*
* We could certainly use this ioctl against EXT4 or XFS, but that's not
* the point we want to illustrate here.
*/
if (info.f_type != BTRFS_SUPER_MAGIC) {
printf("error: you are supposed to be running this against BTRFS;"
" %lx magic detected instead\n", info.f_type);
exit(EXIT_FAILURE);
}
} else {
perror("statfs failed");
exit(EXIT_FAILURE);
}
fd = open(argv[1], O_RDONLY | O_DIRECTORY);
if (fd < 0) {
perror("open");
exit(EXIT_FAILURE);
}
flags = BTRFS_SHUTDOWN_FLAGS_DEFAULT;
if (ioctl(fd, BTRFS_IOC_SHUTDOWN, &flags) == 0) {
printf("Success: filesystem shut down.\n");
} else {
perror("Shutdown failed");
exit(EXIT_FAILURE);
}
close(fd);
return 0;
}
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