linux-kernel - Re: [PATCH] ocfs2: fix check if list iterator did find an element

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Date:   Mon, 21 Mar 2022 19:22:21 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Jakob Koschel <jakobkoschel@...il.com>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Mark Fasheh <mark@...heh.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>,
        Joel Becker <jlbec@...lplan.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Miguel Ojeda <ojeda@...nel.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] ocfs2: fix check if list iterator did find an element

On Mon, Mar 21, 2022 at 04:00:10PM +0000, David Laight wrote:
> From: Dan Carpenter
> > Sent: 21 March 2022 13:55
> > On Mon, Mar 21, 2022 at 02:34:34PM +0100, Jakob Koschel wrote:
> > > >> @@ -556,11 +556,11 @@ static void *lockres_seq_start(struct seq_file *m, loff_t *pos)
> > > >> 		}
> > > >> 	}
> > > >>
> > > >> -	list_for_each_entry(res, track_list, tracking) {
> > > >> -		if (&res->tracking == &dlm->tracking_list)
> > > >> -			res = NULL;
> > > >> -		else
> > > >> -			dlm_lockres_get(res);
> > > >> +	list_for_each_entry(iter, track_list, tracking) {
> > > >> +		if (&iter->tracking != &dlm->tracking_list) {
> > 
> > This is an open coded version of:
> > 
> > 	if (!list_entry_is_head(iter, &dlm->tracking_list, tracking)) {
> 
> Doesn't list_for_each_entry() terminate before that happens?
> So this code is probably still horribly broken.

There is ! in the condition.  It's just a complicated way of writing
if (!0) { so code works fine, it's just messy.

regards,
dan carpenter