linux-kernel - Re: drm pull for v5.3-rc1

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Message-ID: <20190807064000.GC6002@infradead.org>
Date:   Tue, 6 Aug 2019 23:40:00 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>,
        Thomas Hellström (VMware) 
        <thomas@...pmail.org>, Dave Airlie <airlied@...il.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Jerome Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Price <steven.price@....com>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: drm pull for v5.3-rc1

On Tue, Aug 06, 2019 at 12:09:38PM -0700, Matthew Wilcox wrote:
> Has anyone looked at turning the interface inside-out?  ie something like:
> 
> 	struct mm_walk_state state = { .mm = mm, .start = start, .end = end, };
> 
> 	for_each_page_range(&state, page) {
> 		... do something with page ...
> 	}
> 
> with appropriate macrology along the lines of:
> 
> #define for_each_page_range(state, page)				\
> 	while ((page = page_range_walk_next(state)))
> 
> Then you don't need to package anything up into structs that are shared
> between the caller and the iterated function.

I'm not an all that huge fan of super magic macro loops.  But in this
case I don't see how it could even work, as we get special callbacks
for huge pages and holes, and people are trying to add a few more ops
as well.