linux-kernel - Re: [PATCH 1/2] mm/gup: Remove dead pgmap refcounting code

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] [day] [month] [year] [list]

Message-ID: <2eavixbzaofgm7ufqrotoii2ljs3yvz3sax7377k5pjq3q2jgt@m2trxwsnfpo6>
Date: Thu, 4 Sep 2025 09:07:29 +1000
From: Alistair Popple <apopple@...dia.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: linux-mm@...ck.org, akpm@...ux-foundation.org, david@...hat.com, 
	osalvador@...e.de, jhubbard@...dia.com, peterx@...hat.com, 
	linux-kernel@...r.kernel.org, dan.j.williams@...el.com
Subject: Re: [PATCH 1/2] mm/gup: Remove dead pgmap refcounting code

On 2025-09-02 at 22:06 +1000, Jason Gunthorpe <jgg@...pe.ca> wrote...
> On Tue, Sep 02, 2025 at 03:14:20PM +1000, Alistair Popple wrote:
> > Prior to aed877c2b425 ("device/dax: properly refcount device dax pages
> > when mapping") ZONE_DEVICE pages were not fully reference counted when
> > mapped into user page tables. Instead GUP would take a reference on the
> > associated pgmap to ensure the results of pfn_to_page() remained valid.
> > 
> > This is no longer required and most of the code was removed by
> > fd2825b0760a ("mm/gup: remove pXX_devmap usage from get_user_pages()").
> > Finish cleaning this up by removing the dead calls to put_dev_pagemap()
> > and the temporary context struct.
> > 
> > Signed-off-by: Alistair Popple <apopple@...dia.com>
> > ---
> >  mm/gup.c | 67 ++++++++++++++++++++++----------------------------------
> >  1 file changed, 26 insertions(+), 41 deletions(-)
> 
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> 
> Yay! This never made alot of sense :\

Yeah. We could probably get rid of the pagemap refcounting entirely, but that's
on my backlog for now as it doesn't seem super important.

> Jason