Re: [PATCH] drivers/block/ub.c: use list_for_each_entry()

Roland Dreier
2007-05-31T04:28:37Z

> > If I just see
> >
> > for (pos = list_entry((head)->next, typeof(*pos), member),
> > n = list_entry(pos->member.next, typeof(*pos), member);
> > &pos->member != (head);
> > pos = n, n = list_entry(n->member.next, typeof(*n), member))
> >
> > then what am I to think?
>
> You won't catch me writing this kind of crap, so the question is moot.
> Seriously, a comma operator? Admit it, you just expanded a marcro from
> list.h by hand. Real people cannot write like that.

Of course I admit it, that is a copy of the definition of list_for_each_safe()
(with just the '/'s removed). But the point is, if you are writing
something that iterates through a list and deletes entries, you
basically have to write equivalent code.

Just think about how many silly bugs you've written in your life when
(re)implementing linked lists. By using <linux/list.h>, you avoid all
that, and as a code reviewer that makes my life easier. It's the same
theory as <linux/kref.h> -- the code is rather trivial (although as
"git log lib/kref.c" shows, not entirely trivial). But if I see
someone using struct kref, all I have to check is whether she used it
correctly. I don't have to worry about whether she screwed up the
implementation.

- R.