linux-kernel - Re: [PATCH] mm: remove redundant page parameter from do_set

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Message-ID: <aWXFbZJl7Z-9INVp@casper.infradead.org>
Date: Tue, 13 Jan 2026 04:09:17 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Ye Liu <ye.liu@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Ye Liu <liuye@...inos.cn>,
	"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>, Barry Song <baohua@...nel.org>,
	Lance Yang <lance.yang@...ux.dev>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] mm: remove redundant page parameter from do_set_pmd()

On Tue, Jan 13, 2026 at 09:41:29AM +0800, Ye Liu wrote:
> The page parameter passed to do_set_pmd() was always overwritten with
> &folio->page immediately upon function entry (line 5369 in memory.c),
> making the parameter completely redundant. This confused callers who
> computed different page values only to have them ignored.

No.  It's an accident of the implementation that we currently only
support folios up to the size of PMDs.  That is not the long-term plan.
We always want to specify exactly which pages of the folio to map.