linux-kernel - [PATCHv2 1/5] mm/page_vma_mapped: Track if the page is mapped across page table boundary

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Message-ID: <20250919124036.455709-2-kirill@shutemov.name>
Date: Fri, 19 Sep 2025 13:40:32 +0100
From: Kiryl Shutsemau <kirill@...temov.name>
To: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Matthew Wilcox <willy@...radead.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Rik van Riel <riel@...riel.com>,
	Harry Yoo <harry.yoo@...cle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Kiryl Shutsemau <kas@...nel.org>
Subject: [PATCHv2 1/5] mm/page_vma_mapped: Track if the page is mapped across page table boundary

From: Kiryl Shutsemau <kas@...nel.org>

Add a PVMW_PGTABLE_CROSSSED flag that page_vma_mapped_walk() will set if
the page is mapped across page table boundary. Unlike other PVMW_*
flags, this one is result of page_vma_mapped_walk() and not set by the
caller.

folio_referenced_one() will use it detect if it safe to mlock the folio.

Signed-off-by: Kiryl Shutsemau <kas@...nel.org>
---
 include/linux/rmap.h | 5 +++++
 mm/page_vma_mapped.c | 1 +
 2 files changed, 6 insertions(+)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 6cd020eea37a..04797cea3205 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -928,6 +928,11 @@ struct page *make_device_exclusive(struct mm_struct *mm, unsigned long addr,
 /* Look for migration entries rather than present PTEs */
 #define PVMW_MIGRATION		(1 << 1)
 
+/* Result flags */
+
+/* The page is mapped across page boundary */
+#define PVMW_PGTABLE_CROSSSED	(1 << 16)
+
 struct page_vma_mapped_walk {
 	unsigned long pfn;
 	unsigned long nr_pages;
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index e981a1a292d2..a184b88743c3 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -309,6 +309,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 				}
 				pte_unmap(pvmw->pte);
 				pvmw->pte = NULL;
+				pvmw->flags |= PVMW_PGTABLE_CROSSSED;
 				goto restart;
 			}
 			pvmw->pte++;
-- 
2.50.1