mm: thp: fix potential clearing to referenced flag in page_idle_clear_pte_refs_one()

For PTE-mapped THP, the compound THP has not been split to normal 4K pages yet, the whole THP is considered referenced if any one of sub page is referenced.

When walking PTE-mapped THP by pvmw, all relevant PTEs will be checked to retrieve referenced bit. But, the current code just returns the result of the last PTE. If the last PTE has not referenced, the referenced flag will be cleared.

Just set referenced when ptep{pmdp}_clear_young_notify() returns true.

---
v3: Fixed the insane "||" stuff pointed out by Andrew

v2: adopted the suggestion from Kirill. Not use "||=" style to keep checkpatch quiet, otherwise it reports ERROR: spaces required around that '||'

 mm/page_idle.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

index 0a49374..e412a63 100644
@@ -65,11 +65,15 @@ static bool page_idle_clear_pte_refs_one(struct page *page,
 	while (page_vma_mapped_walk(&pvmw)) {
 		addr = pvmw.address;
 		if (pvmw.pte) {
-			referenced = ptep_clear_young_notify(vma, addr,
-					pvmw.pte);
+			/*
+			 * For PTE-mapped THP, one sub page is referenced,
+			 * the whole THP is referenced.
+			 */
+			if (ptep_clear_young_notify(vma, addr, pvmw.pte))
+				referenced = true;
 		} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
-			referenced = pmdp_clear_young_notify(vma, addr,
-					pvmw.pmd);
+			if (pmdp_clear_young_notify(vma, addr, pvmw.pmd))
+				referenced = true;
 		} else {
 			/* unexpected pmd-mapped page? */
 			WARN_ON_ONCE(1);

1.8.3.1

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