Re: [PATCH] Shrink rbtree

[Zach Brown <zach.brown@oracle.com>]

> Maybe. I thought I'd actually done it once before, but I couldn't
> actually find it when I went looking.

Yeah, that's what I remember too.

> Plenty more words in the git commit.

Ah!  of course, thanks.

> They don't make much sense without
> the patch right below them, and you can see them in juxtaposition at 
> http://git.infradead.org/?p=users/dwmw2/rbtree-2.6.git;a=commitdiff;h=1975e59375756da4ff4e6e7d12f67485e813ace0

Indeed, that reasoning looks sound.  First the if (parent) .. else {}
falls away, then the parent left/right relationship is folded into the
test with old.  Looks good.

> I think it's be better just to drop the RB_RED and RB_BLACK definitions.

I'd agree, I figured you'd left them for a reason.

>>> +static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
>>> +{
>> 	BUG_ON((unsigned long)p & 3);
> 
> Yeah, I suppose we could.

>>> +	node->rb_parent_colour = (unsigned long )parent;
>> use rb_set_parent(node, parent) and get the assertion.
> 
> Que?

I meant that if we add the BUG_ON() to rb_set_parent() then we might as
well reuse it here..

- z