linux-kernel - [PATCH v3 0/2] __folio

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Message-ID: <20250714171823.3626213-1-ziy@nvidia.com>
Date: Mon, 14 Jul 2025 13:18:21 -0400
From: Zi Yan <ziy@...dia.com>
To: Balbir Singh <balbirs@...dia.com>,
	David Hildenbrand <david@...hat.com>,
	linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Kirill Shutemov <k.shutemov@...il.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Zi Yan <ziy@...dia.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Nico Pache <npache@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Dev Jain <dev.jain@....com>,
	Barry Song <baohua@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/2] __folio_split() clean up.

Based on the prior discussion[1], this patch improves
__split_unmapped_folio() by making it reusable for splitting unmapped
folios. This helps avoid the need for a new boolean unmapped parameter
to guard mapping-related code.

An additional benefit is that __split_unmapped_folio() could be
called on after-split folios by __folio_split(). It can enable new split
methods. For example, at deferred split time, unmapped subpages can
scatter arbitrarily within a large folio, neither uniform nor non-uniform
split can maximize after-split folio orders for mapped subpages.
The hope is that by calling __split_unmapped_folio() multiple times,
a better split result can be achieved.

It passed mm selftests.

Changelog
===
>From V2[3]:
1. Code format fixes
2. Restructured code to remove after_split goto label.

>From V1[2]:
1. Fixed indentations.
2. Used folio_expected_ref_count() to calculate ref_count instead of
   open coding.

[1] https://lore.kernel.org/linux-mm/94D8C1A4-780C-4BEC-A336-7D3613B54845@nvidia.com/
[2] https://lore.kernel.org/linux-mm/20250711030259.3574392-1-ziy@nvidia.com/
[2] https://lore.kernel.org/linux-mm/20250711182355.3592618-1-ziy@nvidia.com/

Zi Yan (2):
  mm/huge_memory: move unrelated code out of __split_unmapped_folio()
  mm/huge_memory: use folio_expected_ref_count() to calculate ref_count.

 mm/huge_memory.c | 289 +++++++++++++++++++++++------------------------
 1 file changed, 142 insertions(+), 147 deletions(-)

-- 
2.47.2