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#include <sys/mount.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <linux/loop.h>
#include <errno.h>
#define LOOPDEV_MAXLEN 64
#define LOOP_MAJOR 7
static int is_loop(char *dev)
{
struct stat st;
int ret = 0;
if (stat(dev, &st) == 0) {
if (S_ISBLK(st.st_mode) && (major(st.st_rdev) == LOOP_MAJOR)) {
ret = 1;
}
}
return ret;
}
static int is_loop_mount(const char* path, char *loopdev)
{
FILE* f;
int count;
char device[256];
char mount_path[256];
char rest[256];
int result = 0;
f = fopen("/proc/mounts", "r");
if (!f) {
fprintf(stdout, "could not open /proc/mounts: %s\n", strerror(errno));
return -1;
}
do {
count = fscanf(f, "%255s %255s %255s\n", device, mount_path, rest);
if (count == 3) {
if (is_loop(device) && strcmp(path, mount_path) == 0) {
strlcpy(loopdev, device, LOOPDEV_MAXLEN);
result = 1;
break;
}
}
} while (count == 3);
fclose(f);
return result;
}
int umount_main(int argc, char *argv[])
{
int loop, loop_fd;
char loopdev[LOOPDEV_MAXLEN];
if(argc != 2) {
fprintf(stderr,"umount <path>\n");
return 1;
}
loop = is_loop_mount(argv[1], loopdev);
if (umount(argv[1])) {
fprintf(stderr, "failed: %s\n", strerror(errno));
return 1;
}
if (loop) {
// free the loop device
loop_fd = open(loopdev, O_RDONLY);
if (loop_fd < 0) {
fprintf(stderr, "open loop device failed: %s\n", strerror(errno));
return 1;
}
if (ioctl(loop_fd, LOOP_CLR_FD, 0) < 0) {
fprintf(stderr, "ioctl LOOP_CLR_FD failed: %s\n", strerror(errno));
return 1;
}
close(loop_fd);
}
return 0;
}
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