[PATCH 07/35] autonuma: teach gup_fast about pte_numa

Andrea Arcangeli
2012-05-25T17:10:24Z

gup_fast will skip over non present ptes (pte_numa requires the pte to
be non present). So no explicit check is needed for pte_numa in the
pte case.

gup_fast will also automatically skip over THP when the trans huge pmd
is non present (pmd_numa requires the pmd to be non present).

But for the special pmd mode scan of knuma_scand
(/sys/kernel/mm/autonuma/knuma_scand/pmd == 1), the pmd may be of numa
type (so non present too), the pte may be present. gup_pte_range
wouldn't notice the pmd is of numa type. So to avoid losing a NUMA
hinting page fault with gup_fast we need an explicit check for
pmd_numa() here to be sure it will fault through gup ->
handle_mm_fault.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---
arch/x86/mm/gup.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index dd74e46..bf36575 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -164,7 +164,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
* wait_split_huge_page() would never return as the
* tlb flush IPI wouldn't run.
*/
- if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+ if (pmd_none(pmd) || pmd_trans_splitting(pmd) || pmd_numa(pmd))
return 0;
if (unlikely(pmd_large(pmd))) {
if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))