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
37 f = fopen("/proc/mounts", "r");
38 if (!f) {
39 fprintf(stdout, "could not open /proc/mounts: %s\n", strerror(errno));
40 return -1;
41 }
42
43 do {
44 count = fscanf(f, "%255s %255s %255s\n", device, mount_path, rest);
45 if (count == 3) {
46 if (is_loop(device) && strcmp(path, mount_path) == 0) {
47 strlcpy(loopdev, device, LOOPDEV_MAXLEN);
48 result = 1;
49 break;
50 }
51 }
52 } while (count == 3);
53
54 fclose(f);
55 return result;
56 }
57
umount_main(int argc,char * argv[])58 int umount_main(int argc, char *argv[])
59 {
60 int loop, loop_fd;
61 char loopdev[LOOPDEV_MAXLEN];
62
63 if(argc != 2) {
64 fprintf(stderr,"umount <path>\n");
65 return 1;
66 }
67
68 loop = is_loop_mount(argv[1], loopdev);
69 if (umount(argv[1])) {
70 fprintf(stderr, "failed: %s\n", strerror(errno));
71 return 1;
72 }
73
74 if (loop) {
75 // free the loop device
76 loop_fd = open(loopdev, O_RDONLY);
77 if (loop_fd < 0) {
78 fprintf(stderr, "open loop device failed: %s\n", strerror(errno));
79 return 1;
80 }
81 if (ioctl(loop_fd, LOOP_CLR_FD, 0) < 0) {
82 fprintf(stderr, "ioctl LOOP_CLR_FD failed: %s\n", strerror(errno));
83 return 1;
84 }
85
86 close(loop_fd);
87 }
88
89 return 0;
90 }
91