These patches enable userfaultfd support for shared memory mappings. The VMAs backed with shmem/tmpfs can be registered with userfaultfd which allows management of page faults in these areas by userland.
This patch set adds implementation of shmem_mcopy_atomic_pte for proper handling of UFFDIO_COPY command. A callback to handle_userfault is added to shmem page fault handling path. The userfaultfd register/unregister methods are extended to allow shmem VMAs. The UFFDIO_ZEROPAGE and UFFDIO_REGISTER_MODE_WP are not implemented which is reflected by userfaultfd API handshake methods. The patches are based on current Andrea's tree: https://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git Mike Rapoport (7): userfaultfd: introduce vma_can_userfault userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support userfaultfd: shmem: introduce vma_is_shmem userfaultfd: shmem: use shmem_mcopy_atomic_pte for shared memory userfaultfd: shmem: add userfaultfd hook for shared memory faults userfaultfd: shmem: allow registration of shared memory ranges userfaultfd: shmem: add userfaultfd_shmem test fs/userfaultfd.c | 32 ++++--- include/linux/mm.h | 10 +++ include/linux/shmem_fs.h | 11 +++ include/uapi/linux/userfaultfd.h | 2 +- mm/shmem.c | 139 +++++++++++++++++++++++++++++-- mm/userfaultfd.c | 31 ++++--- tools/testing/selftests/vm/Makefile | 3 + tools/testing/selftests/vm/run_vmtests | 11 +++ tools/testing/selftests/vm/userfaultfd.c | 39 ++++++++- 9 files changed, 237 insertions(+), 41 deletions(-) -- 1.9.1
