On Mon, 2012-08-06 at 16:17 +0200, Peter Zijlstra wrote:

Why would every user need to replicate the propagate and rotate
boilerplate?

So I don't have a tree near that any of this applies to (hence no actual
patch), but why can't we have something like:

struct rb_augment_callback {
	const bool (*update)(struct rb_node *node);
	const int offset;
	const int size;
};

#define RB_AUGMENT_CALLBACK(_update, _type, _rb_member, _aug_member)	\
(struct rb_augment_callback){						\
	.update = _update,						\
	.offset = offsetof(_type, _aug_member) - 			\
		  offsetof(_type, _rb_member),				\
	.size   = sizeof(((_type *)NULL)->_aug_member),			\
}

static __always_inline void 
augment_copy(struct rb_node *dst, struct rb_node *src,
	     const rb_augment_callback *ac)
{
	memcpy((void *)dst + ac->offset,
	       (void *)src + ac->offset,
	       ac->size);
} 

static __always_inline void 
augment_propagate(struct rb_node *rb, struct rb_node *stop,
		  const struct rb_augment_callback *ac)
{
	while (rb != stop) {
		if (!ac->update(rb))
			break;
		rb = rb_parent(rb);
	}
}

static __always_inline void
augment_rotate(struct rb_node *old, struct rb_node *new.
	       const struct rb_augment_callback *ac)
{
	augment_copy(new, old, ac);
	(void)ac->update(old);
}


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