On 22.08.24 09:13, Qi Zheng wrote:
In __collapse_huge_page_swapin(), we just use the ptl for pte_same() check
in do_swap_page(). In other places, we directly use pte_offset_map_lock(),
so convert it to using pte_offset_map_ro_nolock().
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
mm/khugepaged.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 4a83c40d90538..53bfa7f4b7f82 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1011,7 +1011,11 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
};
if (!pte++) {
- pte = pte_offset_map_nolock(mm, pmd, address, &ptl);
+ /*
+ * Here the ptl is only used to check pte_same() in
+ * do_swap_page(), so readonly version is enough.
+ */
+ pte = pte_offset_map_ro_nolock(mm, pmd, address, &ptl);
if (!pte) {
mmap_read_unlock(mm);
result = SCAN_PMD_NULL;
Suboptimal that the pteval comparison + unmap is buried in
do_swap_page(). Moving that to the caller is also not significantly
better ...
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Cheers,
David / dhildenb
