mount.c

UNIX/LINUX下面的用户文件系统

    res = umount2(mountpoint, 2);
    if (res == 0)
        return;

    pid = fork();
    if(pid == -1)
        return;

    if(pid == 0) {
        const char *argv[] =
            { FUSERMOUNT_PROG, "-u", "-q", "-z", "--", mountpoint, NULL };

        exec_fusermount(argv);
        _exit(1);
    }
    waitpid(pid, NULL, 0);
}

void fuse_unmount_compat22(const char *mountpoint)
{
    fuse_kern_unmount(mountpoint, -1);
}

static int fuse_mount_fusermount(const char *mountpoint, const char *opts,
                                 int quiet)
{
    int fds[2], pid;
    int res;
    int rv;

    if (!mountpoint) {
        fprintf(stderr, "fuse: missing mountpoint\n");
        return -1;
    }

    res = socketpair(PF_UNIX, SOCK_STREAM, 0, fds);
    if(res == -1) {
        perror("fuse: socketpair() failed");
        return -1;
    }

    pid = fork();
    if(pid == -1) {
        perror("fuse: fork() failed");
        close(fds[0]);
        close(fds[1]);
        return -1;
    }

    if(pid == 0) {
        char env[10];
        const char *argv[32];
        int a = 0;

        if (quiet) {
            int fd = open("/dev/null", O_RDONLY);
            dup2(fd, 1);
            dup2(fd, 2);
        }

        argv[a++] = FUSERMOUNT_PROG;
        if (opts) {
            argv[a++] = "-o";
            argv[a++] = opts;
        }
        argv[a++] = "--";
        argv[a++] = mountpoint;
        argv[a++] = NULL;

        close(fds[1]);
        fcntl(fds[0], F_SETFD, 0);
        snprintf(env, sizeof(env), "%i", fds[0]);
        setenv(FUSE_COMMFD_ENV, env, 1);
        exec_fusermount(argv);
        perror("fuse: failed to exec fusermount");
        _exit(1);
    }

    close(fds[0]);
    rv = receive_fd(fds[1]);
    close(fds[1]);
    waitpid(pid, NULL, 0); /* bury zombie */

    return rv;
}

int fuse_mount_compat22(const char *mountpoint, const char *opts)
{
    return fuse_mount_fusermount(mountpoint, opts, 0);
}

static int fuse_mount_sys(const char *mnt, struct mount_opts *mo,
                          const char *mnt_opts)
{
    char tmp[128];
    const char *devname = "/dev/fuse";
    char *source = NULL;
    char *type = NULL;
    struct stat stbuf;
    int fd;
    int res;

    if (!mnt) {
        fprintf(stderr, "fuse: missing mountpoint\n");
        return -1;
    }

    res = lstat(mnt, &stbuf);
    if (res == -1) {
        fprintf(stderr ,"fuse: failed to access mountpoint %s: %s\n",
                mnt, strerror(errno));
        return -1;
    }

    if (!mo->nonempty) {
        res = fuse_mnt_check_empty("fuse", mnt, stbuf.st_mode, stbuf.st_size);
        if (res == -1)
            return -1;
    }

    fd = open(devname, O_RDWR);
    if (fd == -1) {
        if (errno == ENODEV || errno == ENOENT)
            fprintf(stderr,
                    "fuse: device not found, try 'modprobe fuse' first\n");
        else
            fprintf(stderr, "fuse: failed to open %s: %s\n", devname,
                    strerror(errno));
        return -1;
    }

    snprintf(tmp, sizeof(tmp),  "fd=%i,rootmode=%o,user_id=%i,group_id=%i", fd,
             stbuf.st_mode & S_IFMT, getuid(), getgid());

    res = fuse_opt_add_opt(&mo->kernel_opts, tmp);
    if (res == -1)
        goto out_close;

    source = malloc((mo->fsname ? strlen(mo->fsname) : 0) +
                    (mo->subtype ? strlen(mo->subtype) : 0) +
                    strlen(devname) + 32);

    type = malloc((mo->subtype ? strlen(mo->subtype) : 0) + 32);
    if (!type || !source) {
        fprintf(stderr, "fuse: failed to allocate memory\n");
        goto out_close;
    }

    strcpy(type, mo->blkdev ? "fuseblk" : "fuse");
    if (mo->subtype) {
        strcat(type, ".");
        strcat(type, mo->subtype);
    }
    strcpy(source,
           mo->fsname ? mo->fsname : (mo->subtype ? mo->subtype : devname));

    res = mount(source, mnt, type, mo->flags, mo->kernel_opts);
    if (res == -1 && errno == ENODEV && mo->subtype) {
        /* Probably missing subtype support */
        strcpy(type, mo->blkdev ? "fuseblk" : "fuse");
        if (mo->fsname) {
            if (!mo->blkdev)
                sprintf(source, "%s#%s", mo->subtype, mo->fsname);
        } else {
            strcpy(source, type);
        }
        res = mount(source, mnt, type, mo->flags, mo->kernel_opts);
    }
    if (res == -1) {
        /*
         * Maybe kernel doesn't support unprivileged mounts, in this
         * case try falling back to fusermount
         */
        if (errno == EPERM) {
            res = -2;
        } else {
            int errno_save = errno;
            if (mo->blkdev && errno == ENODEV && !fuse_mnt_check_fuseblk())
                fprintf(stderr, "fuse: 'fuseblk' support missing\n");
            else
                fprintf(stderr, "fuse: mount failed: %s\n",
                        strerror(errno_save));
        }

        goto out_close;
    }

    if (geteuid() == 0) {
        char *newmnt = fuse_mnt_resolve_path("fuse", mnt);
        res = -1;
        if (!newmnt)
            goto out_umount;

        res = fuse_mnt_add_mount("fuse", source, newmnt, type, mnt_opts);
        free(newmnt);
        if (res == -1)
            goto out_umount;
    }

    return fd;

 out_umount:
    umount2(mnt, 2); /* lazy umount */
 out_close:
    free(type);
    free(source);
    close(fd);
    return res;
}

static int get_mnt_flag_opts(char **mnt_optsp, int flags)
{
    int i;

    if (!(flags & MS_RDONLY) && fuse_opt_add_opt(mnt_optsp, "rw") == -1)
        return -1;

    for (i = 0; mount_flags[i].opt != NULL; i++) {
        if (mount_flags[i].on && (flags & mount_flags[i].flag) &&
            fuse_opt_add_opt(mnt_optsp, mount_flags[i].opt) == -1)
            return -1;
    }
    return 0;
}

int fuse_kern_mount(const char *mountpoint, struct fuse_args *args)
{
    struct mount_opts mo;
    int res = -1;
    char *mnt_opts = NULL;

    memset(&mo, 0, sizeof(mo));
    mo.flags = MS_NOSUID | MS_NODEV;

    if (args &&
        fuse_opt_parse(args, &mo, fuse_mount_opts, fuse_mount_opt_proc) == -1)
        return -1;

    if (mo.allow_other && mo.allow_root) {
        fprintf(stderr, "fuse: 'allow_other' and 'allow_root' options are mutually exclusive\n");
        goto out;
    }
    res = 0;
    if (mo.ishelp)
        goto out;

    res = -1;
    if (get_mnt_flag_opts(&mnt_opts, mo.flags) == -1)
        goto out;
    if (mo.kernel_opts && fuse_opt_add_opt(&mnt_opts, mo.kernel_opts) == -1)
        goto out;
    if (mo.mtab_opts &&  fuse_opt_add_opt(&mnt_opts, mo.mtab_opts) == -1)
        goto out;

    res = fuse_mount_sys(mountpoint, &mo, mnt_opts);
    if (res == -2) {
        if (mo.fusermount_opts && 
            fuse_opt_add_opt(&mnt_opts, mo.fusermount_opts) == -1)
            goto out;

        if (mo.subtype) {
            char *tmp_opts = NULL;

            res = -1;
            if (fuse_opt_add_opt(&tmp_opts, mnt_opts) == -1 ||
                fuse_opt_add_opt(&tmp_opts, mo.subtype_opt) == -1) {
                free(tmp_opts);
                goto out;
            }

            res = fuse_mount_fusermount(mountpoint, tmp_opts, 1);
            free(tmp_opts);
            if (res == -1)
                res = fuse_mount_fusermount(mountpoint, mnt_opts, 0);
        } else {
            res = fuse_mount_fusermount(mountpoint, mnt_opts, 0);
        }
    }
 out:
    free(mnt_opts);
    free(mo.fsname);
    free(mo.subtype);
    free(mo.fusermount_opts);
    free(mo.subtype_opt);
    free(mo.kernel_opts);
    free(mo.mtab_opts);
    return res;
}

__asm__(".symver fuse_mount_compat22,fuse_mount@FUSE_2.2");
__asm__(".symver fuse_unmount_compat22,fuse_unmount@FUSE_2.2");