[PATCH 04/18] mm: numa: Do not clear PMD during PTE update scan

[Mel Gorman]

If the PMD is flushed then a parallel fault in handle_mm_fault() will enter
the pmd_none and do_huge_pmd_anonymous_page() path where it'll attempt
to insert a huge zero page. This is wasteful so the patch avoids clearing
the PMD when setting pmd_numa.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
---
 mm/huge_memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index deae592..5a5da50 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1529,7 +1529,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 			 */
 			if (!is_huge_zero_page(page) &&
 			    !pmd_numa(*pmd)) {
-				entry = pmdp_get_and_clear(mm, addr, pmd);
+				entry = *pmd;
 				entry = pmd_mknuma(entry);
 				ret = HPAGE_PMD_NR;
 			}
-- 
1.8.4

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