With fallcoate hole punch now supported by hugetlbfs, users of this functionality would like to catch subsequent faults to holes. The use case is based on a database model where: - Many tasks map the same huegtlbfs file to provide a large shared area - One management task determines that part of this area is no longer used and releases the associated pages by fallocate hole punch - It is an error if any of the tasks fault on the hole userfaultfd can be used to catch faults to the holes, and the application can take appropriate action. This patch set replicates the functionality of the existing userfaultfd routines __mcopy_atomic and mcopy_atomic_pte with modifications for huge pages. The register/unregister routines are modified to accept hugetlb vma's and a hook is added to huge page fault handling. The existing selftest is modified to work with huge pages so that the new code can be exercised and tested. To test the code with selftest, this patch is required: https://lkml.org/lkml/2016/5/31/782 Some issues to consider in the RFC - Is hugetlb.c the best place for hugetlb_mcopy_atomic_pte? - Is there a better way to handle mmap_sem locking on entry/exit to __mcopy_atomic_hugetlb? - Is there a better way to do huge page alignment/sanity checking in the register/unregister routines? Unfortunately, we do not know we are dealing with huge pages until looking at the vma's. - userfaultfd for hugepmd does not support UFFDIO_ZEROPAGE as there is no zero page support for huge pages (except THP case). - Should there be another config option? Support is now provided if both userfaultfd and hugetlb are configured. - This has only been tested on x86, but the code should be arch independent. Mike Kravetz (6): mm/memory: add copy_huge_page_from_user for hugetlb userfaultfd support mm/hugetlb: add hugetlb_mcopy_atomic_pte for userfaultfd support mm/userfaultfd: add __mcopy_atomic_hugetlb for huge page UFFDIO_COPY mm/hugetlb: add userfaultfd hugetlb hook fs/userfaultfd: allow registration of ranges containing huge pages selftests/userfaultfd: add userfaultfd_hugetlb test fs/userfaultfd.c | 69 +++++++++++- include/linux/hugetlb.h | 8 +- include/linux/mm.h | 3 + include/uapi/linux/userfaultfd.h | 3 + mm/hugetlb.c | 102 ++++++++++++++++++ mm/memory.c | 22 ++++ mm/userfaultfd.c | 179 +++++++++++++++++++++++++++++++ tools/testing/selftests/vm/Makefile | 3 + tools/testing/selftests/vm/run_vmtests | 13 +++ tools/testing/selftests/vm/userfaultfd.c | 161 ++++++++++++++++++++++++--- 10 files changed, 540 insertions(+), 23 deletions(-) -- 2.4.11 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>