linux-kernel - Re: [PATCHv3 1/2] mm/memory: Do not populate page table entries beyond i

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Message-ID: <aQWT_6cXWAcjZYON@casper.infradead.org>
Date: Sat, 1 Nov 2025 05:00:47 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Hugh Dickins <hughd@...gle.com>
Cc: Kiryl Shutsemau <kirill@...temov.name>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	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>, Rik van Riel <riel@...riel.com>,
	Harry Yoo <harry.yoo@...cle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	"Darrick J. Wong" <djwong@...nel.org>,
	Dave Chinner <david@...morbit.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 1/2] mm/memory: Do not populate page table entries
 beyond i_size

On Wed, Oct 29, 2025 at 02:45:52AM -0700, Hugh Dickins wrote:
> But you're giving yourself too hard a time of backporting with your
> 5.10 Fixee 01c70267053d for 1/2: the only filesystem which set the
> flag then was tmpfs, which you're now excepting.  The flag got
> renamed later (in 5.16) and then in 5.17 at last there was another
> filesystem to set it.  So, this 1/2 would be
> 
> Fixes: 6795801366da ("xfs: Support large folios")

I haven't been able to keep up with this patchset -- sorry.

But this problem didn't exist until bs>PS support was added because we
would never add a folio to the page cache which extended beyond i_size
before.  We'd shrink the folio order allocated in do_page_cache_ra()
(actually, we still do, but page_cache_ra_unbounded() rounds it up
again).  So it doesn't fix that commit at all, but something far more
recent.