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

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Message-ID: <24272ed3-0d16-412b-a7f4-78d02c347837@lucifer.local>
Date: Tue, 20 May 2025 17:19:26 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Jann Horn <jannh@...gle.com>
Cc: Pedro Falcato <pfalcato@...e.de>,
        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 06:11:49PM +0200, Jann Horn wrote:
> 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.)

Yeah this is true. It is the exception rather than the rule...

>
> (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?)

>From my point of view it simply reads better :)

But perhaps we can drop the fork bit and leave that implied.