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Date:   Tue, 6 Aug 2019 23:40:00 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Christoph Hellwig <hch@infradead.org>,
        Thomas =?iso-8859-1?Q?Hellstr=F6m_=28VMware=29?= 
        <thomas@shipmail.org>, Dave Airlie <airlied@gmail.com>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        LKML <linux-kernel@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Jerome Glisse <jglisse@redhat.com>,
        Jason Gunthorpe <jgg@mellanox.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Steven Price <steven.price@arm.com>,
        Linux-MM <linux-mm@kvack.org>
Subject: Re: drm pull for v5.3-rc1
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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.