linux-kernel - [PATCH V3 2/2] mm/khugepaged: clean up refcount check using folio_expected_ref

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Message-ID: <20250526182818.37978-2-shivankg@amd.com>
Date: Mon, 26 May 2025 18:28:20 +0000
From: Shivank Garg <shivankg@....com>
To: <akpm@...ux-foundation.org>, <david@...hat.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
CC: <ziy@...dia.com>, <baolin.wang@...ux.alibaba.com>,
	<lorenzo.stoakes@...cle.com>, <Liam.Howlett@...cle.com>, <npache@...hat.com>,
	<ryan.roberts@....com>, <dev.jain@....com>, <fengwei.yin@...el.com>,
	<shivankg@....com>, <bharata@....com>
Subject: [PATCH V3 2/2] mm/khugepaged: clean up refcount check using folio_expected_ref_count()

Use folio_expected_ref_count() instead of open-coded logic in
is_refcount_suitable(). This avoids code duplication and improves
clarity.

Drop is_refcount_suitable() as it is no longer needed.

Suggested-by: David Hildenbrand <david@...hat.com>
Acked-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Shivank Garg <shivankg@....com>
---
 mm/khugepaged.c | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index fe1fe7eace54..685eb949f4ce 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -548,19 +548,6 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte,
 	}
 }
 
-static bool is_refcount_suitable(struct folio *folio)
-{
-	int expected_refcount = folio_mapcount(folio);
-
-	if (!folio_test_anon(folio) || folio_test_swapcache(folio))
-		expected_refcount += folio_nr_pages(folio);
-
-	if (folio_test_private(folio))
-		expected_refcount++;
-
-	return folio_ref_count(folio) == expected_refcount;
-}
-
 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 					unsigned long address,
 					pte_t *pte,
@@ -652,7 +639,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		 * but not from this process. The other process cannot write to
 		 * the page, only trigger CoW.
 		 */
-		if (!is_refcount_suitable(folio)) {
+		if (folio_expected_ref_count(folio) != folio_ref_count(folio)) {
 			folio_unlock(folio);
 			result = SCAN_PAGE_COUNT;
 			goto out;
@@ -1402,7 +1389,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 		 * has excessive GUP pins (i.e. 512).  Anyway the same check
 		 * will be done again later the risk seems low.
 		 */
-		if (!is_refcount_suitable(folio)) {
+		if (folio_expected_ref_count(folio) != folio_ref_count(folio)) {
 			result = SCAN_PAGE_COUNT;
 			goto out_unmap;
 		}
-- 
2.34.1