linux-kernel - Re: [PATCH net-next v4 02/18] net: dsa: sja1105: remove use of iterator after list_for_each

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Message-ID: <725e814d-da65-b77d-1a6e-a029d594944f@gmail.com>
Date:   Sat, 16 Apr 2022 12:40:00 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jakob Koschel <jakobkoschel@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Jiri Pirko <jiri@...nulli.us>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Casper Andersson <casper.casan@...il.com>,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Arnd Bergmann <arnd@...db.de>,
        Colin Ian King <colin.king@...el.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Xu Wang <vulab@...as.ac.cn>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, bpf@...r.kernel.org,
        Mike Rapoport <rppt@...nel.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH net-next v4 02/18] net: dsa: sja1105: remove use of
 iterator after list_for_each_entry() loop



On 4/15/2022 5:29 AM, Jakob Koschel wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> The link below explains that there is a desire to syntactically change
> list_for_each_entry() and list_for_each() such that it becomes
> impossible to use the iterator variable outside the scope of the loop.
> 
> Although sja1105_insert_gate_entry() makes legitimate use of the
> iterator pointer when it breaks out, the pattern it uses may become
> illegal, so it needs to change.
> 
> It is deemed acceptable to use a copy of the loop iterator, and
> sja1105_insert_gate_entry() only needs to know the list_head element
> before which the list insertion should be made. So let's profit from the
> occasion and refactor the list iteration to a dedicated function.
> 
> An additional benefit is given by the fact that with the helper function
> in place, we no longer need to special-case the empty list, since it is
> equivalent to not having found any gating entry larger than the
> specified interval in the list. We just need to insert at the tail of
> that list (list_add vs list_add_tail on an empty list does the same
> thing).
> 
> Link: https://patchwork.kernel.org/project/netdevbpf/patch/20220407102900.3086255-3-jakobkoschel@gmail.com/#24810127
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian