linux-kernel - Re: [PATCH v3 1/7] kernel/fork: convert vma assignment to a memcpy

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Message-ID: <CAJuCfpG5HyMP3RM1jTJxCnN4WUz4APAcxbkOT48ZtJDXcb3z3w@mail.gmail.com>
Date:   Wed, 25 Jan 2023 16:50:01 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
        vbabka@...e.cz, hannes@...xchg.org, mgorman@...hsingularity.net,
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Subject: Re: [PATCH v3 1/7] kernel/fork: convert vma assignment to a memcpy

On Wed, Jan 25, 2023 at 4:22 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 25 Jan 2023 15:35:48 -0800 Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> > Convert vma assignment in vm_area_dup() to a memcpy() to prevent compiler
> > errors when we add a const modifier to vma->vm_flags.
> >
> > ...
> >
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -482,7 +482,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
> >                * orig->shared.rb may be modified concurrently, but the clone
> >                * will be reinitialized.
> >                */
> > -             *new = data_race(*orig);
> > +             memcpy(new, orig, sizeof(*new));
>
> The data_race() removal is unchangelogged?

True. I'll add a note in the changelog about that. Ideally I would
like to preserve it but I could not find a way to do that.

>
> >               INIT_LIST_HEAD(&new->anon_vma_chain);
> >               dup_anon_vma_name(orig, new);
> >       }
>