linux-kernel - [PATCH v1 14/18] mm/migrate_device: use folio_mapcount() in migrate_vma_check

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Date: Tue,  9 Apr 2024 21:22:57 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	linux-doc@...r.kernel.org,
	cgroups@...r.kernel.org,
	linux-sh@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Peter Xu <peterx@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Yin Fengwei <fengwei.yin@...el.com>,
	Yang Shi <shy828301@...il.com>,
	Zi Yan <ziy@...dia.com>,
	Jonathan Corbet <corbet@....net>,
	Hugh Dickins <hughd@...gle.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Rich Felker <dalias@...c.org>,
	John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
	Chris Zankel <chris@...kel.net>,
	Max Filippov <jcmvbkbc@...il.com>,
	Muchun Song <muchun.song@...ux.dev>,
	Miaohe Lin <linmiaohe@...wei.com>,
	Naoya Horiguchi <naoya.horiguchi@....com>,
	Richard Chang <richardycc@...gle.com>
Subject: [PATCH v1 14/18] mm/migrate_device: use folio_mapcount() in migrate_vma_check_page()

We want to limit the use of page_mapcount() to the places where it is
absolutely necessary. Let's convert migrate_vma_check_page() to work on
a folio internally so we can remove the page_mapcount() usage.

Note that we reject any large folios.

There is a lot more folio conversion to be had, but that has to wait for
another day. No functional change intended.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/migrate_device.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index d40b46ae9d65..b929b450b77c 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -324,6 +324,8 @@ static void migrate_vma_collect(struct migrate_vma *migrate)
  */
 static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
 {
+	struct folio *folio = page_folio(page);
+
 	/*
 	 * One extra ref because caller holds an extra reference, either from
 	 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
@@ -336,18 +338,18 @@ static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
 	 * check them than regular pages, because they can be mapped with a pmd
 	 * or with a pte (split pte mapping).
 	 */
-	if (PageCompound(page))
+	if (folio_test_large(folio))
 		return false;
 
 	/* Page from ZONE_DEVICE have one extra reference */
-	if (is_zone_device_page(page))
+	if (folio_is_zone_device(folio))
 		extra++;
 
 	/* For file back page */
-	if (page_mapping(page))
-		extra += 1 + page_has_private(page);
+	if (folio_mapping(folio))
+		extra += 1 + folio_has_private(folio);
 
-	if ((page_count(page) - extra) > page_mapcount(page))
+	if ((folio_ref_count(folio) - extra) > folio_mapcount(folio))
 		return false;
 
 	return true;
-- 
2.44.0