[PATCH v3 3/3] mm/mmu_notifier: contextual information for event triggering invalidation v2

[Dan Williams]

On Thu, Dec 13, 2018 at 9:14 AM <jglisse at redhat.com> wrote:
>
> From: Jérôme Glisse <jglisse at redhat.com>
>
> CPU page table update can happens for many reasons, not only as a result
> of a syscall (munmap(), mprotect(), mremap(), madvise(), ...) but also
> as a result of kernel activities (memory compression, reclaim, migration,
> ...).
>
> Users of mmu notifier API track changes to the CPU page table and take
> specific action for them. While current API only provide range of virtual
> address affected by the change, not why the changes is happening.
>
> This patchset adds event information so that users of mmu notifier can
> differentiate among broad category:
>     - UNMAP: munmap() or mremap()
>     - CLEAR: page table is cleared (migration, compaction, reclaim, ...)
>     - PROTECTION_VMA: change in access protections for the range
>     - PROTECTION_PAGE: change in access protections for page in the range
>     - SOFT_DIRTY: soft dirtyness tracking
>
> Being able to identify munmap() and mremap() from other reasons why the
> page table is cleared is important to allow user of mmu notifier to
> update their own internal tracking structure accordingly (on munmap or
> mremap it is not longer needed to track range of virtual address as it
> becomes invalid).

Who consumes these new enum values? The consumer of the new
infrastructure should be included in the patchset that adds the new
functionality. So a NAK from me until the consumer is clarified /
included.