linux-kernel - Re: [PATCH 2/5] mm/mseal: move madvise() logic to mm/madvise.c

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Message-ID: <nnm4cmygbeyzwxfwqduo5lq3d5cthuic5irof2l3tb5x43n2hz@mmjklktcfk2o>
Date: Mon, 14 Jul 2025 16:31:59 +0100
From: Pedro Falcato <pfalcato@...e.de>
To: David Hildenbrand <david@...hat.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Jeff Xu <jeffxu@...omium.org>
Subject: Re: [PATCH 2/5] mm/mseal: move madvise() logic to mm/madvise.c

On Mon, Jul 14, 2025 at 05:03:03PM +0200, David Hildenbrand wrote:
> [...] 
> 
> But now I wonder, why is it okay to discard anon pages in a MAP_PRIVATE file
> mapping?

IIRC this was originally suggested by Linus, on one of the versions introducing
mseal. But the gist is that discarding pages is okay if you could already zero
them manually, using e.g memset. Hence the writeability checks.

-- 
Pedro