linux-kernel - Re: [PATCH v2 1/4] mm/huge_memory: change folio_split_supported() to folio_check

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Message-ID: <20251123015025.cbwijhb6rhvtuxzu@master>
Date: Sun, 23 Nov 2025 01:50:25 +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 1/4] mm/huge_memory: change folio_split_supported() to
 folio_check_splittable()

On Fri, Nov 21, 2025 at 09:55:26PM -0500, Zi Yan wrote:
>folio_split_supported() used in try_folio_split_to_order() requires
>folio->mapping to be non NULL, but current try_folio_split_to_order() does
>not check it. There is no issue in the current code, since
>try_folio_split_to_order() is only used in truncate_inode_partial_folio(),
>where folio->mapping is not NULL.
>
>To prevent future misuse, move folio->mapping NULL check (i.e., folio is
>truncated) into folio_split_supported(). Since folio->mapping NULL check
>returns -EBUSY and folio_split_supported() == false means -EINVAL, change
>folio_split_supported() return type from bool to int and return error
>numbers accordingly. Rename folio_split_supported() to
>folio_check_splittable() to match the return type change.
>
>While at it, move is_huge_zero_folio() check and folio_test_writeback()
>check into folio_check_splittable() and add kernel-doc.
>
>Signed-off-by: Zi Yan <ziy@...dia.com>

LGTM, Thanks

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


-- 
Wei Yang
Help you, Help me