[PATCH 3.8 085/166] mm: clear pmd_numa before invalidating

Kamal Mostafa
2014-01-15T21:51:39Z

From: Mel Gorman <mgorman@suse.de>

commit 67f87463d3a3362424efcbe8b40e4772fd34fc61 upstream.

On x86, PMD entries are similar to _PAGE_PROTNONE protection and are
handled as NUMA hinting faults. The following two page table protection
bits are what defines them

_PAGE_NUMA:set _PAGE_PRESENT:clear

A PMD is considered present if any of the _PAGE_PRESENT, _PAGE_PROTNONE,
_PAGE_PSE or _PAGE_NUMA bits are set. If pmdp_invalidate encounters a
pmd_numa, it clears the present bit leaving _PAGE_NUMA which will be
considered not present by the CPU but present by pmd_present. The
existing caller of pmdp_invalidate should handle it but it's an
inconsistent state for a PMD. This patch keeps the state consistent
when calling pmdp_invalidate.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
mm/pgtable-generic.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 0c8323f..eb900bb 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -166,6 +166,9 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm)
void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)
{
+ pmd_t entry = *pmdp;
+ if (pmd_numa(entry))
+ entry = pmd_mknonnuma(entry);
set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(*pmdp));
flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
}
--
1.8.3.2