linux-kernel - Re: [PATCH net-next v5 4/4] net: add per-netns sysctl for devmem autorelease

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Message-ID: <aQEyQVyRIchjkfFd@devvm11784.nha0.facebook.com>
Date: Tue, 28 Oct 2025 14:14:41 -0700
From: Bobby Eshleman <bobbyeshleman@...il.com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	David Ahern <dsahern@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bobby Eshleman <bobbyeshleman@...a.com>
Subject: Re: [PATCH net-next v5 4/4] net: add per-netns sysctl for devmem
 autorelease

On Mon, Oct 27, 2025 at 06:22:16PM -0700, Mina Almasry wrote:
> On Thu, Oct 23, 2025 at 2:00 PM Bobby Eshleman <bobbyeshleman@...il.com> wrote:

[...]

> > diff --git a/net/core/devmem.c b/net/core/devmem.c
> > index 8f3199fe0f7b..9cd6d93676f9 100644
> > --- a/net/core/devmem.c
> > +++ b/net/core/devmem.c
> > @@ -331,7 +331,7 @@ net_devmem_bind_dmabuf(struct net_device *dev,
> >                 goto err_free_chunks;
> >
> >         list_add(&binding->list, &priv->bindings);
> > -       binding->autorelease = true;
> > +       binding->autorelease = dev_net(dev)->core.sysctl_devmem_autorelease;
> >
> 
> Do you need to READ_ONCE this and WRITE_ONCE the write site? Or is
> that silly for a u8? Maybe better be safe.

Probably worth it to be safe.
> 
> Could we not make this an optional netlink argument? I thought that
> was a bit nicer than a sysctl.
> 
> Needs a doc update.
> 
> 
> -- Thanks, Mina

Sounds good, I'll change to nl for the next rev. Thanks for the review!

Best,
Bobby