linux-kernel - Re: [PATCH net v2] ip6mr: Fix lockdep and sparse RCU warnings

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Message-ID: <CANn89iLC5SgSgCEJfu7npgK22h+U3zOJzAd1kv0drEOmF24a3A@mail.gmail.com>
Date: Tue, 1 Oct 2024 15:26:49 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Stefan Wiehler <stefan.wiehler@...ia.com>
Cc: "David S . Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Petr Malat <oss@...at.biz>
Subject: Re: [PATCH net v2] ip6mr: Fix lockdep and sparse RCU warnings

On Tue, Oct 1, 2024 at 2:50 PM Stefan Wiehler <stefan.wiehler@...ia.com> wrote:
>
> > OK, but RT6_TABLE_DFLT always exists, ip6mr_get_table(net, RT6_TABLE_DFLT)
> > can never fail.
> >
> > This is ensured at netns creation, from ip6mr_rules_init()
>
> OK, but nevertheless we need to enter a RCU read-side critical section before
> ip6mr_get_table() is called.

This could be a lockdep annotation error then, at least for
RT6_TABLE_DFLT, oh well.

Note that net/ipv4/ipmr.c would have a similar issue.

Please split your patch in small units, their Fixes: tags are likely
different, and if some code breaks something,
fixing the issue will be easier.

The changelog seemed to only address the first ip6mr_vif_seq_start() part.