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

[Linus Torvalds]

On Sun, Dec 19, 2021 at 2:02 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> I'd like to get rid of ->mapcount for file pages too.  And those are
> definitely never mapped in the majority of cases.

Fair enough.

You'd probably be better off checking "is this mapping mapped" though.
Because otherwise you have to get the page lock to serialize each
page.

               Linus