[PATCH 1/3] mmu_notifier: Add mmu_notifier_invalidate_range()

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>

This notifier closes an important gap with the current
invalidate_range_start()/end() notifiers. The _start() part
is called when all pages are still mapped while the _end()
notifier is called when all pages are potentially unmapped
and already freed.

This does not allow to manage external (non-CPU) hardware
TLBs with MMU-notifiers because there is no way to prevent
that hardware will establish new TLB entries between the
calls of these two functions. But this is a requirement to
the subsytem that implements these existing notifiers.

To allow managing external TLBs the MMU-notifiers need to
catch the moment when pages are unmapped but not yet freed.
This new notifier catches that moment and notifies the
interested subsytem when pages that were unmapped are about
to be freed. The new notifier will only be called between
invalidate_range_start()/end().

Signed-off-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
---
 include/linux/mmu_notifier.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index deca874..f333668 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -228,6 +228,11 @@ static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 		__mmu_notifier_invalidate_range_start(mm, start, end);
 }
 
+static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
+				  unsigned long start, unsigned long end)
+{
+}
+
 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 				  unsigned long start, unsigned long end)
 {
@@ -321,6 +326,11 @@ static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 {
 }
 
+static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
+				  unsigned long start, unsigned long end)
+{
+}
+
 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 				  unsigned long start, unsigned long end)
 {
-- 
1.9.1