linux-kernel - [PATCH v3 0/3] mm/huge_memory: vmf_insert_folio_*() and vmf_insert_pfn

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Message-ID: <20250613092702.1943533-1-david@redhat.com>
Date: Fri, 13 Jun 2025 11:26:59 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	nvdimm@...ts.linux.dev,
	linux-cxl@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alistair Popple <apopple@...dia.com>,
	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>,
	Zi Yan <ziy@...dia.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Nico Pache <npache@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Dev Jain <dev.jain@....com>,
	Dan Williams <dan.j.williams@...el.com>,
	Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v3 0/3] mm/huge_memory: vmf_insert_folio_*() and vmf_insert_pfn_pud() fixes

Based on mm/mm-unstable.

While working on improving vm_normal_page() and friends, I stumbled
over this issues: refcounted "normal" folios must not be marked
using pmd_special() / pud_special(). Otherwise, we're effectively telling
the system that these folios are no "normal", violating the rules we
documented for vm_normal_page().

Fortunately, there are not many pmd_special()/pud_special() users yet.
So far there doesn't seem to be serious damage.

Tested using the ndctl tests ("ndctl:dax" suite).

v2 -> v3:
* Added tags (thanks for all the review!)
* Smaller fixups (add empty lines) and patch description improvements

v1 -> v2:
* "mm/huge_memory: don't ignore queried cachemode in vmf_insert_pfn_pud()"
 -> Added after stumbling over that
* Modified the other tests to reuse the existing function by passing a
  new struct
* Renamed the patches to talk about "folios" instead of pages and adjusted
  the patch descriptions
* Dropped RB/TB from Dan and Oscar due to the changes

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Mike Rapoport <rppt@...nel.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: Nico Pache <npache@...hat.com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: Dev Jain <dev.jain@....com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Oscar Salvador <osalvador@...e.de>

David Hildenbrand (3):
  mm/huge_memory: don't ignore queried cachemode in vmf_insert_pfn_pud()
  mm/huge_memory: don't mark refcounted folios special in
    vmf_insert_folio_pmd()
  mm/huge_memory: don't mark refcounted folios special in
    vmf_insert_folio_pud()

 include/linux/mm.h |  19 +++++++-
 mm/huge_memory.c   | 112 ++++++++++++++++++++++++++++-----------------
 2 files changed, 87 insertions(+), 44 deletions(-)

-- 
2.49.0