netdev - Re: [PATCH net-next] scm: optimize put

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Message-ID: <CANn89iKqQ0at-hyWZq5EOZOUMTjL7PvZOB_k3KRA8acbGzQy5w@mail.gmail.com>
Date:   Fri, 16 Apr 2021 20:36:36 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [PATCH net-next] scm: optimize put_cmsg()

On Fri, Apr 16, 2021 at 8:29 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Fri, 16 Apr 2021 20:28:40 +0200 Eric Dumazet wrote:
> > On Fri, Apr 16, 2021 at 7:57 PM Jakub Kicinski <kuba@...nel.org> wrote:
> > >
> > > On Thu, 15 Apr 2021 10:37:53 -0700 Eric Dumazet wrote:
> > > > From: Eric Dumazet <edumazet@...gle.com>
> > > >
> > > > Calling two copy_to_user() for very small regions has very high overhead.
> > > >
> > > > Switch to inlined unsafe_put_user() to save one stac/clac sequence,
> > > > and avoid copy_to_user().
> > > >
> > > > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > > > Cc: Soheil Hassas Yeganeh <soheil@...gle.com>
> > >
> > > Hi Eric!
> > >
> > > This appears to break boot on my systems.
> > >
> > > IDK how exactly, looks like systemd gets stuck waiting for nondescript
> > > services to start in initramfs. I have lots of debug enabled and didn't
> > > spot anything of note in kernel logs.
> > >
> > > I'll try to poke at this more, but LMK if you have any ideas. The
> > > commit looks "obviously correct" :S
> >
> > Oops, my rebase went wong, sorry for that
>
> Ah, my eyes failed to spot that :)
>
> > Can you check this  patch (on top of the buggy one) ?
> >
> > If that works, I'll submit a v2
>
> It's already merged. Let me try the fix now...

I have sent the official patch, thanks for this fast feedback !