How to get the physical address in 2MB/1GB Hugepages?

Question

I have carefully studied this question (How to get the physical address of a huge-page) and some references(https://shanetully.com/2014/12/translating-virtual-addresses-to-physcial-addresses-in-user-space/#codeprocpidpagemapcode and https://www.kernel.org/doc/Documentation/vm/pagemap.txt), but they don't help, so I ask again.

I know how to get the physical address by /proc/self/pagemap. In short, it is divided into two steps: 1. Get the physical page and 2. Get the page offset.

uint64_t get_page_frame_number_of_address(void *address) {

    /* Open the pagemap file for the current process */
    FILE *pagemap = fopen("/proc/self/pagemap", "rb");

    /* Seek to the page that the buffer is on it */ 
    uint64_t offset = (uint64_t)((uint64_t)address >> PAGE_SHIFT) * (uint64_t)PAGEMAP_LENGTH;
    if(fseek(pagemap, (uint64_t)offset, SEEK_SET) != 0) {
        fprintf(stderr, "Failed to seek pagemap to proper location\n");
        exit(1);
    }

    /* The page frame number is in bits 0-54 so read the first 7 bytes and clear the 55th bit */
    uint64_t page_frame_number = 0;
    fread(&page_frame_number, 1, PAGEMAP_LENGTH-1, pagemap);
    page_frame_number &= 0x7FFFFFFFFFFFFF;
    fclose(pagemap);
    return page_frame_number;
}

uint64_t get_physical_address(void* address) {

    /* Get page frame number */
    unsigned int page_frame_number = get_page_frame_number_of_address(address);

    /* Find the difference from the buffer to the page boundary */
    uint64_t distance_from_page_boundary = (uint64_t)address % getpagesize();

    /* Determine how far to seek into memory to find the buffer */
    uint64_t physical_address = (uint64_t)((uint64_t)page_frame_number << PAGE_SHIFT) + (uint64_t)distance_from_page_boundary;

    return physical_address;
}

I tried changing page_shift from 12 (4KB) to 21 (2MB) and the size of getpagesize(), but then my page_frame_number is always 0. Therefore, I wonder if the physical address in HugePage cannot be obtained by /proc/self/pagemap? And Is there any other way to obtain the physical address of HugePage?