linux-kernel - Re: [PATCH v22 1/4] mm: add MAP_DROPPABLE for designating always lazily freeable mappings

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: <ZpAcWvij59AzUD9u@zx2c4.com>
Date: Thu, 11 Jul 2024 19:54:34 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: David Hildenbrand <david@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
	tglx@...utronix.de, linux-crypto@...r.kernel.org,
	linux-api@...r.kernel.org, x86@...nel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>,
	Carlos O'Donell <carlos@...hat.com>,
	Florian Weimer <fweimer@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	Jann Horn <jannh@...gle.com>,
	Christian Brauner <brauner@...nel.org>,
	David Hildenbrand <dhildenb@...hat.com>, linux-mm@...ck.org
Subject: Re: [PATCH v22 1/4] mm: add MAP_DROPPABLE for designating always
 lazily freeable mappings

On Thu, Jul 11, 2024 at 07:27:27PM +0200, David Hildenbrand wrote:
> > PG_owner_priv_1 maps to PG_swapcache? :)
> 
> Maybe the combination !swapbacked && swapcache could be used to indicate 
> such folios. (we will never set swapbacked)
> 
> But likely we have to be a bit careful here. We don't want 
> folio_test_swapcache() to return for folios that ... are not in the 
> swapcache.

I was thinking that too, but I'm afraid it's going to be another
whack-a-mole nightmare. Even for things like task_mmu in procfs that
show stats, that's going to be wonky.

Any other flags we can overload that aren't going to be already used in
our case?

Jason