linux-kernel - Re: [PATCH RFC 07/14] fs/dax: use vmf_insert_folio

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: <74acb38f-da34-448d-9b73-37433a5e342c@redhat.com>
Date: Wed, 25 Jun 2025 11:03:11 +0200
From: David Hildenbrand <david@...hat.com>
To: Alistair Popple <apopple@...dia.com>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-mm@...ck.org, nvdimm@...ts.linux.dev,
 Andrew Morton <akpm@...ux-foundation.org>, Juergen Gross <jgross@...e.com>,
 Stefano Stabellini <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
 Dan Williams <dan.j.williams@...el.com>, Matthew Wilcox
 <willy@...radead.org>, Jan Kara <jack@...e.cz>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>, Zi Yan <ziy@...dia.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.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>, Vlastimil Babka <vbabka@...e.cz>,
 Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Jann Horn <jannh@...gle.com>,
 Pedro Falcato <pfalcato@...e.de>
Subject: Re: [PATCH RFC 07/14] fs/dax: use vmf_insert_folio_pmd() to insert
 the huge zero folio

On 24.06.25 03:16, Alistair Popple wrote:
> On Tue, Jun 17, 2025 at 05:43:38PM +0200, David Hildenbrand wrote:
>> Let's convert to vmf_insert_folio_pmd().
>>
>> In the unlikely case there is already something mapped, we'll now still
>> call trace_dax_pmd_load_hole() and return VM_FAULT_NOPAGE.
>>
>> That should probably be fine, no need to add special cases for that.
> 
> I'm not sure about that. Consider dax_iomap_pmd_fault() -> dax_fault_iter() ->
> dax_pmd_load_hole(). It calls split_huge_pmd() in response to VM_FAULT_FALLBACK
> which will no longer happen, what makes that ok?

My reasoning was that this is the exact same behavior other 
vmf_insert_folio_pmd() users here would result in.

But let me dig into the details.

-- 
Cheers,

David / dhildenb