linux-kernel - Re: [PATCH v2 3/4] mm/huge_memory: make min_order_for

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251123015317.3pommq5h54xnau7e@master>
Date: Sun, 23 Nov 2025 01:53:17 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Zi Yan <ziy@...dia.com>
Cc: David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	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>,
	Lance Yang <lance.yang@...ux.dev>,
	Miaohe Lin <linmiaohe@...wei.com>,
	Naoya Horiguchi <nao.horiguchi@...il.com>,
	Wei Yang <richard.weiyang@...il.com>,
	Balbir Singh <balbirs@...dia.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] mm/huge_memory: make min_order_for_split() always
 return an order

On Fri, Nov 21, 2025 at 09:55:28PM -0500, Zi Yan wrote:
>min_order_for_split() returns -EBUSY when the folio is truncated and cannot
>be split. In commit 77008e1b2ef7 ("mm/huge_memory: do not change
>split_huge_page*() target order silently"), memory_failure() does not
>handle it and pass -EBUSY to try_to_split_thp_page() directly.
>try_to_split_thp_page() returns -EINVAL since -EBUSY becomes 0xfffffff0 as
>new_order is unsigned int in __folio_split() and this large new_order is
>rejected as an invalid input. The code does not cause a bug.
>soft_offline_in_use_page() also uses min_order_for_split() but it always
>passes 0 as new_order for split.
>
>Fix it by making min_order_for_split() always return an order. When the
>given folio is truncated, namely folio->mapping == NULL, return 0 and let
>a subsequent split function handle the situation and return -EBUSY.
>
>Add kernel-doc to min_order_for_split() to clarify its use.
>
>Signed-off-by: Zi Yan <ziy@...dia.com>

LGTM, Thanks

Reviewed-by: Wei Yang <richard.weiyang@...il.com>

-- 
Wei Yang
Help you, Help me