mm/mmu_notifier: contextual information for event enums

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,
...).

This patch introduce a set of enums that can be associated with each of
the events triggering a mmu notifier.  Latter patches take advantages of
those enum values.

    - 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).

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jérôme Glisse <[email protected]>
Reviewed-by: Ralph Campbell <[email protected]>
Reviewed-by: Ira Weiny <[email protected]>
Cc: Christian König <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Felix Kuehling <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krcmar <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Christian Koenig <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 30 insertions, 0 deletions

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index c8672c366f67..2386e71ac1b8 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -10,6 +10,36 @@
 struct mmu_notifier;
 struct mmu_notifier_ops;
 
+/**
+ * enum mmu_notifier_event - reason for the mmu notifier callback
+ * @MMU_NOTIFY_UNMAP: either munmap() that unmap the range or a mremap() that
+ * move the range
+ *
+ * @MMU_NOTIFY_CLEAR: clear page table entry (many reasons for this like
+ * madvise() or replacing a page by another one, ...).
+ *
+ * @MMU_NOTIFY_PROTECTION_VMA: update is due to protection change for the range
+ * ie using the vma access permission (vm_page_prot) to update the whole range
+ * is enough no need to inspect changes to the CPU page table (mprotect()
+ * syscall)
+ *
+ * @MMU_NOTIFY_PROTECTION_PAGE: update is due to change in read/write flag for
+ * pages in the range so to mirror those changes the user must inspect the CPU
+ * page table (from the end callback).
+ *
+ * @MMU_NOTIFY_SOFT_DIRTY: soft dirty accounting (still same page and same
+ * access flags). User should soft dirty the page in the end callback to make
+ * sure that anyone relying on soft dirtyness catch pages that might be written
+ * through non CPU mappings.
+ */
+enum mmu_notifier_event {
+	MMU_NOTIFY_UNMAP = 0,
+	MMU_NOTIFY_CLEAR,
+	MMU_NOTIFY_PROTECTION_VMA,
+	MMU_NOTIFY_PROTECTION_PAGE,
+	MMU_NOTIFY_SOFT_DIRTY,
+};
+
 #ifdef CONFIG_MMU_NOTIFIER
 
 /*