linux-kernel - [PATCHv2 07/14] mm: Make page

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Message-ID: <20251218150949.721480-8-kas@kernel.org>
Date: Thu, 18 Dec 2025 15:09:38 +0000
From: Kiryl Shutsemau <kas@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Muchun Song <muchun.song@...ux.dev>,
	David Hildenbrand <david@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	Usama Arif <usamaarif642@...il.com>,
	Frank van der Linden <fvdl@...gle.com>
Cc: Oscar Salvador <osalvador@...e.de>,
	Mike Rapoport <rppt@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Zi Yan <ziy@...dia.com>,
	Baoquan He <bhe@...hat.com>,
	Michal Hocko <mhocko@...e.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Jonathan Corbet <corbet@....net>,
	kernel-team@...a.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	Kiryl Shutsemau <kas@...nel.org>
Subject: [PATCHv2 07/14] mm: Make page_zonenum() use head page

With the upcoming changes to HVO, a single page of tail struct pages
will be shared across all huge pages of the same order on a node. Since
huge pages on the same node may belong to different zones, the zone
information stored in shared tail page flags would be incorrect.

Always fetch zone information from the head page, which has unique and
correct zone flags for each compound page.

Signed-off-by: Kiryl Shutsemau <kas@...nel.org>
---
 include/linux/mmzone.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9f44dc760cdc..7e4f69b9d760 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1224,6 +1224,7 @@ static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags)
 
 static inline enum zone_type page_zonenum(const struct page *page)
 {
+	page = compound_head(page);
 	return memdesc_zonenum(page->flags);
 }
 
-- 
2.51.2