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

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Message-ID: <a40547f1-3a47-4ba0-8b7e-8f74f91a6b6d@redhat.com>
Date: Tue, 20 May 2025 18:35:00 +0200
From: David Hildenbrand <david@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Jann Horn <jannh@...gle.com>
Cc: Pedro Falcato <pfalcato@...e.de>,
 Andrew Morton <akpm@...ux-foundation.org>,
 "Liam R . Howlett" <Liam.Howlett@...cle.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 20.05.25 18:19, Lorenzo Stoakes wrote:
> 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.

Yes, we should. Exec is where the "fun" begins.

-- 
Cheers,

David / dhildenb