linux-kernel - [PATCH v2 4/4] khugepaged: fix wrong result value for trace_mm_collapse_huge_page

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Date:   Fri, 5 Mar 2021 22:29:47 -0500
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <kirill.shutemov@...ux.intel.com>
CC:     <riel@...hat.com>, <ebru.akagunduz@...il.com>,
        <dan.carpenter@...cle.com>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, <linmiaohe@...wei.com>
Subject: [PATCH v2 4/4] khugepaged: fix wrong result value for trace_mm_collapse_huge_page_isolate()

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.

Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/khugepaged.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e886a8618c33..adf677246d86 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -716,17 +716,17 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		if (pte_write(pteval))
 			writable = true;
 	}
-	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, compound_pagelist);
 	trace_mm_collapse_huge_page_isolate(page, none_or_zero,
-- 
2.19.1