[PATCH 5.4 080/141] khugepaged: fix wrong result value for trace_mm_collapse_huge_page_isolate()

[Greg Kroah-Hartman]

From: Miaohe Lin <linmiaohe@xxxxxxxxxx>

[ Upstream commit 74e579bf231a337ab3786d59e64bc94f45ca7b3f ]

In writable and !referenced case, the result value should be
SCAN_LACK_REFERENCED_PAGE for trace_mm_collapse_huge_page_isolate()
instead of default 0 (SCAN_FAIL) here.

Link: https://lkml.kernel.org/r/20210306032947.35921-5-linmiaohe@xxxxxxxxxx
Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/khugepaged.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f0d7e6483ba3..3c2326568193 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -628,17 +628,17 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		    mmu_notifier_test_young(vma->vm_mm, address))
 			referenced++;
 	}
-	if (likely(writable)) {
-		if (likely(referenced)) {
-			result = SCAN_SUCCEED;
-			trace_mm_collapse_huge_page_isolate(page, none_or_zero,
-							    referenced, writable, result);
-			return 1;
-		}
-	} else {
+
+	if (unlikely(!writable)) {
 		result = SCAN_PAGE_RO;
+	} else if (unlikely(!referenced)) {
+		result = SCAN_LACK_REFERENCED_PAGE;
+	} else {
+		result = SCAN_SUCCEED;
+		trace_mm_collapse_huge_page_isolate(page, none_or_zero,
+						    referenced, writable, result);
+		return 1;
 	}
-
 out:
 	release_pte_pages(pte, _pte);
 	trace_mm_collapse_huge_page_isolate(page, none_or_zero,
-- 
2.30.2