linux-kernel - Re: [PATCH net-next v4 07/18] net: dsa: Replace usage of found with dedicated list iterator variable

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Message-ID: <20220415160452.z4m4j3sulcteqggs@skbuf>
Date:   Fri, 15 Apr 2022 19:04:52 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Jakob Koschel <jakobkoschel@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...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>
Subject: Re: [PATCH net-next v4 07/18] net: dsa: Replace usage of found with
 dedicated list iterator variable

On Fri, Apr 15, 2022 at 02:29:36PM +0200, Jakob Koschel wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
> 
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate iterator variable instead of a
> found boolean [1].
> 
> This removes the need to use a found variable and simply checking if
> the variable was set, can determine if the break/goto was hit.
> 
> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
> Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
> ---

I absolutely hate the robotic commit message, but the change looks like
it works, so:

Reviewed-by: Vladimir Oltean <olteanv@...il.com>

>  net/dsa/dsa.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> index 89c6c86e746f..645522c4dd4a 100644
> --- a/net/dsa/dsa.c
> +++ b/net/dsa/dsa.c
> @@ -112,22 +112,21 @@ const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf)
>  
>  const struct dsa_device_ops *dsa_tag_driver_get(int tag_protocol)
>  {
> -	struct dsa_tag_driver *dsa_tag_driver;
> +	struct dsa_tag_driver *dsa_tag_driver = NULL, *iter;
>  	const struct dsa_device_ops *ops;
> -	bool found = false;
>  
>  	request_module("%s%d", DSA_TAG_DRIVER_ALIAS, tag_protocol);
>  
>  	mutex_lock(&dsa_tag_drivers_lock);
> -	list_for_each_entry(dsa_tag_driver, &dsa_tag_drivers_list, list) {
> -		ops = dsa_tag_driver->ops;
> +	list_for_each_entry(iter, &dsa_tag_drivers_list, list) {
> +		ops = iter->ops;
>  		if (ops->proto == tag_protocol) {
> -			found = true;
> +			dsa_tag_driver = iter;
>  			break;
>  		}
>  	}
>  
> -	if (found) {
> +	if (dsa_tag_driver) {
>  		if (!try_module_get(dsa_tag_driver->owner))
>  			ops = ERR_PTR(-ENOPROTOOPT);
>  	} else {
> -- 
> 2.25.1
>