Lose umount to toybox.

    start \

    stop \

    top \

    umount \

    uptime \

    watchprops \

#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;

}