memfd and transparent hugepages

[Avi Kivity <avi@scylladb.com>]

#define _GNU_SOURCE
#include <sys/mman.h>
#include <linux/memfd.h>
#include <unistd.h>
#include <stddef.h>

int main(int ac, char** av) {
    size_t memsz = (size_t)2048 << 20;
    int fd = memfd_create("memory", MFD_CLOEXEC);
    ftruncate(fd, memsz);
    void* p = mmap((void*)0x40000000, memsz, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FILE, fd, 0);
    madvise(p, memsz, MADV_HUGEPAGE);
    madvise(p, memsz, MADV_POPULATE_WRITE);
    madvise(p, memsz, MADV_COLLAPSE);
    pause();
    return 0;
}

While memfd is documented as using anonymous pages, AnonHugePages shows
as zero.

If memfd incompatible with transparent hugepages?