linux-kernel - Re: [PATCH 2/5] userfaultfd, shmem: use a VMA callback to handle UFFDIO

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Message-ID: <aSW9MJJ1CF65m5w9@kernel.org>
Date: Tue, 25 Nov 2025 16:29:04 +0200
From: Mike Rapoport <rppt@...nel.org>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: linux-mm@...ck.org, Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Axel Rasmussen <axelrasmussen@...gle.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Hugh Dickins <hughd@...gle.com>,
	James Houghton <jthoughton@...gle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Michal Hocko <mhocko@...e.com>,
	Nikita Kalyazin <kalyazin@...zon.com>,
	Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Shuah Khan <shuah@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/5] userfaultfd, shmem: use a VMA callback to handle
 UFFDIO_CONTINUE

On Mon, Nov 24, 2025 at 12:03:17PM +0100, David Hildenbrand (Red Hat) wrote:
> On 11/23/25 11:27, Mike Rapoport wrote:
> > From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
> > 
> > When userspace resolves a page fault in a shmem VMA with UFFDIO_CONTINUE
> > it needs to get a folio that already exists in the pagecache backing
> > that VMA.
> > 
> > Instead of using shmem_get_folio() for that, add a get_pagecache_folio()
> 
> get_shared_folio()
> 
> Given that the helper now no longer receives a VMA, I assume we can just
> really call it get_folio() and the "shared" part would be implicit. (from
> the inode)

It makes naming shmem_vm_ops.get_folio harder, because we already have
shmem_get_folio :)
I'll think of something.

> -- 
> Cheers
> David

-- 
Sincerely yours,
Mike.