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SubjectRe: [RFC PATCH 0/5] userfaultfd: non-cooperative: better tracking for mapping changes
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On January 24, 2017 9:52 PM Mike Rapoport wrote:
> Hi,
>
> These patches try to address issues I've encountered during integration of
> userfaultfd with CRIU.
> Previously added userfaultfd events for fork(), madvise() and mremap()
> unfortunately do not cover all possible changes to a process virtual memory
> layout required for uffd monitor.
> When one or more VMAs is removed from the process mm, the external uffd
> monitor has no way to detect those changes and will attempt to fill the
> removed regions with userfaultfd_copy.
> Another problematic event is the exit() of the process. Here again, the
> external uffd monitor will try to use userfaultfd_copy, although mm owning
> the memory has already gone.
>
> The first patch in the series is a minor cleanup and it's not strictly
> related to the rest of the series.
>
> The patches 2 and 3 below add UFFD_EVENT_UNMAP and UFFD_EVENT_EXIT to allow
> the uffd monitor track changes in the memory layout of a process.
>
> The patches 4 and 5 amend error codes returned by userfaultfd_copy to make
> the uffd monitor able to cope with races that might occur between delivery
> of unmap and exit events and outstanding userfaultfd_copy's.
>
> The patches are agains current -mm tree.
>
> Mike Rapoport (5):
> mm: call vm_munmap in munmap syscall instead of using open coded version
> userfaultfd: non-cooperative: add event for memory unmaps
> userfaultfd: non-cooperative: add event for exit() notification
> userfaultfd: mcopy_atomic: return -ENOENT when no compatible VMA found
> userfaultfd_copy: return -ENOSPC in case mm has gone
>
> arch/tile/mm/elf.c | 2 +-
> arch/x86/entry/vdso/vma.c | 2 +-
> arch/x86/mm/mpx.c | 2 +-
> fs/aio.c | 2 +-
> fs/proc/vmcore.c | 4 +-
> fs/userfaultfd.c | 91 ++++++++++++++++++++++++++++++++++++++++
> include/linux/mm.h | 14 ++++---
> include/linux/userfaultfd_k.h | 25 +++++++++++
> include/uapi/linux/userfaultfd.h | 8 +++-
> ipc/shm.c | 6 +--
> kernel/exit.c | 2 +
> mm/mmap.c | 55 ++++++++++++++----------
> mm/mremap.c | 23 ++++++----
> mm/userfaultfd.c | 42 ++++++++++---------
> mm/util.c | 5 ++-
> 15 files changed, 215 insertions(+), 68 deletions(-)
>
> --
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>


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