commit 5a6dac3ec5f583cc8ee7bc53b5500a207c4ca433 upstream.
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.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Alex Thorlton <athorlton@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 90cd2c3..5003349 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1474,20 +1474,22 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
if (__pmd_trans_huge_lock(pmd, vma) == 1) {
pmd_t entry;
- entry = pmdp_get_and_clear(mm, addr, pmd);
if (!prot_numa) {
+ entry = pmdp_get_and_clear(mm, addr, pmd);
entry = pmd_modify(entry, newprot);
BUG_ON(pmd_write(entry));
+ set_pmd_at(mm, addr, pmd, entry);
} else {
struct page *page = pmd_page(*pmd);
+ entry = *pmd;
/* only check non-shared pages */
if (page_mapcount(page) == 1 &&
!pmd_numa(*pmd)) {
entry = pmd_mknuma(entry);
+ set_pmd_at(mm, addr, pmd, entry);
}
}
- set_pmd_at(mm, addr, pmd, entry);
spin_unlock(&vma->vm_mm->page_table_lock);
ret = 1;
}
--
1.8.4
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