Re: [PATCH 5/5] mm/thp: Split huge pmds/puds if they're pinned when fork()

Peter Xu
2020-09-24T15:48:01Z

On Wed, Sep 23, 2020 at 09:07:49AM -0700, Yang Shi wrote:
> For tmpfs map, the pmd split just clears the pmd entry without
> reinstalling ptes (oppositely anonymous map would reinstall ptes). It
> looks this patch intends to copy at pte level by splitting pmd. But
> I'm afraid this may not work for tmpfs mappings.

IIUC that's exactly what we want.

We only want to make sure the pinned tmpfs shared pages will be kept there in
the parent. It's not a must to copy the pages to the child, as long as they
can be faulted in later correctly.

--
Peter Xu