Re: [PATCH 1/5] mm: Introduce mm_struct.has_pinned

Peter Xu
2020-09-28T17:13:30Z

On Sun, Sep 27, 2020 at 11:16:34AM -0700, Linus Torvalds wrote:
> - split up the "copy page" into its own function kind of like I had
> done for my minimal patch

I didn't do that majorly because of the wrprotect() (of the fast-gup race) that
can potentially be kept if it's a normal cow. Maybe we'd add one more comment
above the caller of copy_present_page() (even if we have a "NOTE!" section
already inside the helper) since it'll change *src_pte and it's hard to notice
from the function name "copy_present_page()". Not that important, though.

Thanks for doing the changes. I went over the whole patch and it looks indeed
cleaner than before (I also didn't spot anything wrong either).

Regarding the other even rarer "hardware race on dirty/access bits" - maybe we
can simply set all these two bits always when page copy happens and we want to
recover the ptes? I also agree it's trivial enough, so that maybe we even
don't need to care about that.

--
Peter Xu