linux-kernel - [PATCHv2 0/5] mm: Improve mlock tracking for large folios

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Message-ID: <20250919124036.455709-1-kirill@shutemov.name>
Date: Fri, 19 Sep 2025 13:40:31 +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 0/5] mm: Improve mlock tracking for large folios

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

The patchset includes several fixes and improvements related to mlock
tracking of large folios.

The main objective is to reduce the undercount of Mlocked memory in
/proc/meminfo and improve the accuracy of the statistics.

Patches 1-2:

These patches address a minor race condition in folio_referenced_one()
related to mlock_vma_folio().

Currently, mlock_vma_folio() is called on large folio without the page
table lock, which can result in a race condition with unmap (i.e.
MADV_DONTNEED). This can lead to partially mapped folios on the
unevictable LRU list.

While not a significant issue, I do not believe backporting is
necessary.

Patch 3:

This patch adds mlocking logic similar to folio_referenced_one() to
try_to_unmap_one(), allowing for mlocking of large folios where
possible.

Patch 4:

This patch modifies finish_fault() to fault in the entire folio when
possible, enabling efficient mlocking upon addition to the rmap.

Patch 5:

This patch ensures that rmap mlocks large folios if they are fully
mapped, addressing the primary source of mlock undercount for large
folios.

Kiryl Shutsemau (5):
  mm/page_vma_mapped: Track if the page is mapped across page table
    boundary
  mm/rmap: Fix a mlock race condition in folio_referenced_one()
  mm/rmap: mlock large folios in try_to_unmap_one()
  mm/fault: Try to map the entire file folio in finish_fault()
  mm/rmap: Improve mlock tracking for large folios

 include/linux/rmap.h |   5 +++
 mm/memory.c          |   9 +---
 mm/page_vma_mapped.c |   1 +
 mm/rmap.c            | 101 +++++++++++++++++++++++--------------------
 4 files changed, 61 insertions(+), 55 deletions(-)

-- 
2.50.1