Re: [PATCH v1 06/11] mm: support GUP-triggered unsharing via FAULT_FLAG_UNSHARE (!hugetlb)

[Linus Torvalds]

On Mon, Dec 20, 2021 at 10:37 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> This might be a step in the right direction?
>
> Subject: [PATCH] mm: reuse_swap_page() no longer needs to return map_swapcount

Well, that patch seems to be a no-op removal of dead code, so absolutely yes.

That said, I think it would be good to split it up. I looked at that
patch and went "is that really a no-op" to the point of recreating it.

I think it would be good to make it multiple patches that are each
individally trivial. IOW, start with

 (1) remove second argument to reuse_swap_page() that is always NULL,
without making any other changes

 (2) that now made 'total_mapcount' unused in reuse_swap_page(),
remove it as an argument from page_trans_huge_map_swapcount()

 (3) that now made 'total_mapcount' unused in
page_trans_huge_mapcount(), remove it as an argument there too.

because as it stands, that patch of yours looks like it is changing a
lot of things, and I think it would be clearer to remove one thign at
a time as it becomes obviously not used.

Hmm?

           Linus