linux-kernel - Re: [RFC PATCH 4/5] mm/madvise: add PMADV_SET_FORK_EXEC_DEFAULT process

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Message-ID: <CAG48ez2+UEifqF=GRat0dStPfDNXzzewHU=zxj0+FbOXL=mKVQ@mail.gmail.com>
Date: Tue, 20 May 2025 18:11:49 +0200
From: Jann Horn <jannh@...gle.com>
To: Pedro Falcato <pfalcato@...e.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R . Howlett" <Liam.Howlett@...cle.com>, David Hildenbrand <david@...hat.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Arnd Bergmann <arnd@...db.de>, Christian Brauner <brauner@...nel.org>, 
	linux-mm@...ck.org, linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, 
	SeongJae Park <sj@...nel.org>, Usama Arif <usamaarif642@...il.com>
Subject: Re: [RFC PATCH 4/5] mm/madvise: add PMADV_SET_FORK_EXEC_DEFAULT
 process_madvise() flag

On Tue, May 20, 2025 at 10:38 AM Pedro Falcato <pfalcato@...e.de> wrote:
> - PMADV_INHERIT_FORK. This makes it so the flag is propagated to child processes (does not imply PMADV_FUTURE)

Do we think there will be flags settable through this API that we
explicitly _don't_ want to inherit on fork()? My understanding is that
sort of the default for fork() is to inherit everything, and things
that don't get inherited are weird special cases (like mlock() state).
(While the default for execve() is to inherit nothing about the MM.)

(I guess you could make a case that in a fork+exec sequence, the child
might not want to create hugepage between fork and exec... but this is
probably not the right place to control that?)