From: Rik van Riel <redacted>

If ptep_clear_flush() is called to clear a page table entry that is
accessible anyway by the CPU, eg. a _PAGE_PROTNONE page table entry,
there is no need to flush the TLB on remote CPUs.

Signed-off-by: Rik van Riel <redacted>
Signed-off-by: Peter Zijlstra <redacted>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 mm/pgtable-generic.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: tip/mm/pgtable-generic.c
===================================================================

--- tip.orig/mm/pgtable-generic.c
+++ tip/mm/pgtable-generic.c

@@ -88,7 +88,8 @@ pte_t ptep_clear_flush(struct vm_area_st
 {
 	pte_t pte;
 	pte = ptep_get_and_clear((vma)->vm_mm, address, ptep);
-	flush_tlb_page(vma, address);
+	if (pte_accessible(pte))
+		flush_tlb_page(vma, address);
 	return pte;
 }
 #endif


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