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

[Matthew Wilcox]

On Mon, Dec 20, 2021 at 11:15:14AM -0800, Linus Torvalds wrote:
> 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.

Hah, that was actually how I did it originally (without actually
committing at each step, and with a few "Oh, hang on, now we can avoid
calculating this too" stops and restarts along the way), but I thought
it all hung together logically as a single change.  It's hard to see
things from the other person's perspective at times.