mm: Only flush the TLB when clearing an accessible pte

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 <riel@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hugh Dickins <hughd@google.com>
Link: http://lkml.kernel.org/n/tip-vm3rkzevahelwhejx5uwm8ex@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index d8397da42fe6476aad2ae5d89c1b00194963edb9..0c8323fe6c8f610b4068a2232eb4459c23f765f6 100644 (file)
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -88,7 +88,8 @@ pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,
 {
        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