[RFC PATCH 2/2] mm: mmu_notifier fix for tlb_end_vma

[Nicholas Piggin]

The generic tlb_end_vma does not call invalidate_range mmu notifier,
and it resets resets the mmu_gather range, which means the notifier
won't be called on part of the range in case of an unmap that spans
multiple vmas.

ARM64 seems to be the only arch I could see that has notifiers and
uses the generic tlb_end_vma. I have not actually tested it.

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 include/asm-generic/tlb.h | 17 +++++++++++++----
 mm/memory.c               | 10 ----------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index e811ef7b8350..79cb76b89c26 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -15,6 +15,7 @@
 #ifndef _ASM_GENERIC__TLB_H
 #define _ASM_GENERIC__TLB_H
 
+#include <linux/mmu_notifier.h>
 #include <linux/swap.h>
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
@@ -138,6 +139,16 @@ static inline void __tlb_reset_range(struct mmu_gather 
*tlb)
        }
 }
 
+static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
+{
+       if (!tlb->end)
+               return;
+
+       tlb_flush(tlb);
+       mmu_notifier_invalidate_range(tlb->mm, tlb->start, tlb->end);
+       __tlb_reset_range(tlb);
+}
+
 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
                                        struct page *page, int page_size)
 {
@@ -186,10 +197,8 @@ static inline void 
tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 
 #define __tlb_end_vma(tlb, vma)                                        \
        do {                                                    \
-               if (!tlb->fullmm && tlb->end) {                 \
-                       tlb_flush(tlb);                         \
-                       __tlb_reset_range(tlb);                 \
-               }                                               \
+               if (!tlb->fullmm)                               \
+                       tlb_flush_mmu_tlbonly(tlb);             \
        } while (0)
 
 #ifndef tlb_end_vma
diff --git a/mm/memory.c b/mm/memory.c
index 7c58310734eb..c4a7b6cb17c8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -238,16 +238,6 @@ void arch_tlb_gather_mmu(struct mmu_gather *tlb, struct 
mm_struct *mm,
        __tlb_reset_range(tlb);
 }
 
-static void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
-{
-       if (!tlb->end)
-               return;
-
-       tlb_flush(tlb);
-       mmu_notifier_invalidate_range(tlb->mm, tlb->start, tlb->end);
-       __tlb_reset_range(tlb);
-}
-
 static void tlb_flush_mmu_free(struct mmu_gather *tlb)
 {
        struct mmu_gather_batch *batch;
-- 
2.17.0