Re: [PATCH drm-next v2 03/16] maple_tree: split up MA_STATE() macro

[Matthew Wilcox <willy@infradead.org>]

On Fri, Feb 17, 2023 at 02:44:09PM +0100, Danilo Krummrich wrote:
> \#define SAMPLE_ITER(name, __mgr) \
> 	struct sample_iter name = { \
> 		.mas = __MA_STATE(&(__mgr)->mt, 0, 0),

This is usually called MA_STATE_INIT()

> #define sample_iter_for_each_range(it__, start__, end__) \
> 	for ((it__).mas.index = start__, (it__).entry = mas_find(&(it__).mas, end__ - 1); \
> 	     (it__).entry; (it__).entry = mas_find(&(it__).mas, end__ - 1))

This is a bad iterator design.  It's usually best to do this:

	struct sample *sample;
	SAMPLE_ITERATOR(si, min);

	sample_iter_for_each(&si, sample, max) {
		frob(mgr, sample);
	}

I don't mind splitting apart MA_STATE_INIT from MA_STATE, and if you
do that, we can also use it in VMA_ITERATOR.