Re: [PATCH v2 1/4] mm/mremap: Optimize the start addresses in move_page_tables()

[Joel Fernandes]

On Sat, May 20, 2023 at 12:01 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, May 19, 2023 at 8:57 PM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote:
> >
> > I also realize that I don't really need to check whether the masked
> > source address falls under a VMA neighboring to that of the source's.
>
> I don't think that's true.
>
> You can't start randomly moving other source vma's that may have other contents.

If the beginning part of the PMD is not mapped at the destination, I
thought maybe a whole PMD could be moved to it. But I guess not
because we don't want those contents to be accessible. So then in that
case we have to forbid the optimization for all intra-VMA moves except
those involving the stack. I will think more about it.

Thanks,

 - Joel