MIME-Version: 1.0
References: <20230125233554.153109-1-surenb@google.com> <20230125233554.153109-2-surenb@google.com>
 <20230125162159.a66e5ef05fecb405e85ffec9@linux-foundation.org>
In-Reply-To: <20230125162159.a66e5ef05fecb405e85ffec9@linux-foundation.org>
From:   Suren Baghdasaryan <surenb@google.com>
Date:   Wed, 25 Jan 2023 16:50:01 -0800
Message-ID: <CAJuCfpG5HyMP3RM1jTJxCnN4WUz4APAcxbkOT48ZtJDXcb3z3w@mail.gmail.com>
Subject: Re: [PATCH v3 1/7] kernel/fork: convert vma assignment to a memcpy
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
        vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net,
        dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com,
        peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org,
        mingo@redhat.com, will@kernel.org, luto@kernel.org,
        songliubraving@fb.com, peterx@redhat.com, david@redhat.com,
        dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de,
        kent.overstreet@linux.dev, punit.agrawal@bytedance.com,
        lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com,
        axelrasmussen@google.com, joelaf@google.com, minchan@google.com,
        jannh@google.com, shakeelb@google.com, tatashin@google.com,
        edumazet@google.com, gthelen@google.com, gurua@google.com,
        arjunroy@google.com, soheil@google.com, hughlynch@google.com,
        leewalsh@google.com, posk@google.com, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, kernel-team@android.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Jan 25, 2023 at 4:22 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 25 Jan 2023 15:35:48 -0800 Suren Baghdasaryan <surenb@google.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);
> >       }
>