static int process_config(VolumeManager *vm) {
    std::string path(android::vold::DefaultFstabPath()); //獲取到vold.fstab檔案路徑
    fstab = fs_mgr_read_fstab(path.c_str());//解析.fstab檔案，並返回封裝的fstab物件
    if (!fstab) {
        PLOG(ERROR) << "Failed to open default fstab " << path;
        return -1;
    }

    /* Loop through entries looking for ones that vold manages */
    bool has_adoptable = false;
    for (int i = 0; i < fstab->num_entries; i++) {
        if (fs_mgr_is_voldmanaged(&fstab->recs[i])) {
            if (fs_mgr_is_nonremovable(&fstab->recs[i])) {
                LOG(WARNING) << "nonremovable no longer supported; ignoring volume";
                continue;
            }

            std::string sysPattern(fstab->recs[i].blk_device);
            std::string nickname(fstab->recs[i].label);
            int flags = 0;

            if (fs_mgr_is_encryptable(&fstab->recs[i])) {
                flags |= android::vold::Disk::Flags::kAdoptable;
                has_adoptable = true;
            }
            if (fs_mgr_is_noemulatedsd(&fstab->recs[i])
                    || property_get_bool("vold.debug.default_primary", false)) {
                flags |= android::vold::Disk::Flags::kDefaultPrimary;//is Primary?
            }

            vm->addDiskSource(std::shared_ptr<VolumeManager::DiskSource>(
                    new VolumeManager::DiskSource(sysPattern, nickname, flags)));//新增一個VolumeManager::DiskSource物件，儲存了一些資訊
        }
    }
    property_set("vold.has_adoptable", has_adoptable ? "1" : "0");
    return 0;
}
 

//解析.fstab配置檔案，並返回一個fstab結構物件
struct fstab *fs_mgr_read_fstab(const char *fstab_path)
{
    FILE *fstab_file;
    int cnt, entries;
    ssize_t len;
    size_t alloc_len = 0;
    char *line = NULL;
    const char *delim = " \t";
    char *save_ptr, *p;
    struct fstab *fstab = NULL;
    struct fs_mgr_flag_values flag_vals;
#define FS_OPTIONS_LEN 1024
    char tmp_fs_options[FS_OPTIONS_LEN];

    fstab_file = fopen(fstab_path, "r");
    if (!fstab_file) {
        ERROR("Cannot open file %s\n", fstab_path);
        return 0;
    }

    entries = 0;
    while ((len = getline(&line, &alloc_len, fstab_file)) != -1) {
        /* if the last character is a newline, shorten the string by 1 byte */
        if (line[len - 1] == '\n') {
            line[len - 1] = '\0';
        }
        /* Skip any leading whitespace */
        p = line;
        while (isspace(*p)) {
            p++;
        }
        /* ignore comments or empty lines */
        if (*p == '#' || *p == '\0')
            continue;
        entries++;
    }

    if (!entries) {
        ERROR("No entries found in fstab\n");
        goto err;
    }

    /* Allocate and init the fstab structure */
    fstab = calloc(1, sizeof(struct fstab));
    fstab->num_entries = entries;
    fstab->fstab_filename = strdup(fstab_path);
    fstab->recs = calloc(fstab->num_entries, sizeof(struct fstab_rec));

    fseek(fstab_file, 0, SEEK_SET);

    cnt = 0;
	//解析fstab中每行的內容，並進行封裝
    while ((len = getline(&line, &alloc_len, fstab_file)) != -1) {
        /* if the last character is a newline, shorten the string by 1 byte */
        if (line[len - 1] == '\n') {
            line[len - 1] = '\0';
        }

        /* Skip any leading whitespace */
        p = line;
        while (isspace(*p)) {
            p++;
        }
        /* ignore comments or empty lines */
        if (*p == '#' || *p == '\0')
            continue;

        /* If a non-comment entry is greater than the size we allocated, give an
         * error and quit.  This can happen in the unlikely case the file changes
         * between the two reads.
         */
        if (cnt >= entries) {
            ERROR("Tried to process more entries than counted\n");
            break;
        }

        if (!(p = strtok_r(line, delim, &save_ptr))) {
            ERROR("Error parsing mount source\n");
            goto err;
        }
        fstab->recs[cnt].blk_device = strdup(p);

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing mount_point\n");
            goto err;
        }
        fstab->recs[cnt].mount_point = strdup(p);//mount的位置

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing fs_type\n");
            goto err;
        }
        fstab->recs[cnt].fs_type = strdup(p);

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing mount_flags\n");
            goto err;
        }
        tmp_fs_options[0] = '\0';
        fstab->recs[cnt].flags = parse_flags(p, mount_flags, NULL,
                                       tmp_fs_options, FS_OPTIONS_LEN);

        /* fs_options are optional */
        if (tmp_fs_options[0]) {
            fstab->recs[cnt].fs_options = strdup(tmp_fs_options);
        } else {
            fstab->recs[cnt].fs_options = NULL;
        }

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing fs_mgr_options\n");
            goto err;
        }
        fstab->recs[cnt].fs_mgr_flags = parse_flags(p, fs_mgr_flags,
                                                    &flag_vals, NULL, 0);
        fstab->recs[cnt].key_loc = flag_vals.key_loc;
        fstab->recs[cnt].verity_loc = flag_vals.verity_loc;
        fstab->recs[cnt].length = flag_vals.part_length;
        fstab->recs[cnt].label = flag_vals.label;
        fstab->recs[cnt].partnum = flag_vals.partnum;
        fstab->recs[cnt].swap_prio = flag_vals.swap_prio;
        fstab->recs[cnt].zram_size = flag_vals.zram_size;
        cnt++;
    }
    fclose(fstab_file);
    free(line);
    return fstab;

err:
    fclose(fstab_file);
    free(line);
    if (fstab)
        fs_mgr_free_fstab(fstab);
    return NULL;
}