1
2 #include <sys/mount.h>
3 #include <sys/stat.h>
4 #include <fcntl.h>
5 #include <stdio.h>
6 #include <string.h>
7 #include <unistd.h>
8 #include <linux/loop.h>
9 #include <errno.h>
10
11 #define LOOPDEV_MAXLEN 64
12 #define LOOP_MAJOR 7
13
is_loop(char * dev)14 static int is_loop(char *dev)
15 {
16 struct stat st;
17 int ret = 0;
18
19 if (stat(dev, &st) == 0) {
20 if (S_ISBLK(st.st_mode) && (major(st.st_rdev) == LOOP_MAJOR)) {
21 ret = 1;
22 }
23 }
24
25 return ret;
26 }
27
is_loop_mount(const char * path,char * loopdev)28 static int is_loop_mount(const char* path, char *loopdev)
29 {
30 FILE* f;
31 int count;
32 char device[256];
33 char mount_path[256];
34 char rest[256];
35 int result = 0;
36 int path_length = strlen(path);
37
38 f = fopen("/proc/mounts", "r");
39 if (!f) {
40 fprintf(stdout, "could not open /proc/mounts: %s\n", strerror(errno));
41 return -1;
42 }
43
44 do {
45 count = fscanf(f, "%255s %255s %255s\n", device, mount_path, rest);
46 if (count == 3) {
47 if (is_loop(device) && strcmp(path, mount_path) == 0) {
48 strlcpy(loopdev, device, LOOPDEV_MAXLEN);
49 result = 1;
50 break;
51 }
52 }
53 } while (count == 3);
54
55 fclose(f);
56 return result;
57 }
58
umount_main(int argc,char * argv[])59 int umount_main(int argc, char *argv[])
60 {
61 int loop, loop_fd;
62 char loopdev[LOOPDEV_MAXLEN];
63
64 if(argc != 2) {
65 fprintf(stderr,"umount <path>\n");
66 return 1;
67 }
68
69 loop = is_loop_mount(argv[1], loopdev);
70 if (umount(argv[1])) {
71 fprintf(stderr, "failed: %s\n", strerror(errno));
72 return 1;
73 }
74
75 if (loop) {
76 // free the loop device
77 loop_fd = open(loopdev, O_RDONLY);
78 if (loop_fd < 0) {
79 fprintf(stderr, "open loop device failed: %s\n", strerror(errno));
80 return 1;
81 }
82 if (ioctl(loop_fd, LOOP_CLR_FD, 0) < 0) {
83 fprintf(stderr, "ioctl LOOP_CLR_FD failed: %s\n", strerror(errno));
84 return 1;
85 }
86
87 close(loop_fd);
88 }
89
90 return 0;
91 }
92