Re: [PATCH 0/3 v2] fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions

[Andrei Vagin]

On Mon, Mar 31, 2025 at 4:26 AM Lorenzo Stoakes
<lorenzo.stoakes@xxxxxxxxxx> wrote:
>
> On Mon, Mar 24, 2025 at 06:53:25AM +0000, Andrei Vagin wrote:
> > Introduce the PAGE_IS_GUARD flag in the PAGEMAP_SCAN ioctl to expose
> > information about guard regions. This allows userspace tools, such as
> > CRIU, to detect and handle guard regions.
> >
> > Currently, CRIU utilizes PAGEMAP_SCAN as a more efficient alternative to
> > parsing /proc/pid/pagemap. Without this change, guard regions are
> > incorrectly reported as swap-anon regions, leading CRIU to attempt
> > dumping them and subsequently failing.
> >
> > This series should be applied on top of "[PATCH 0/2] fs/proc/task_mmu:
> > add guard region bit to pagemap":
> > https://lore.kernel.org/all/2025031926-engraved-footer-3e9b@gregkh/T/
> >
> > The series includes updates to the documentation and selftests to
> > reflect the new functionality.
> >
> > v2:
> > - sync linux/fs.h with the kernel sources
> > - address comments from Lorenzo and David.
>
> Thanks, sorry for delay, LSF/MM/BPF is why :)

Yep, I know. I hope it was productive. You mentioned in another thread that
you are going to handle compatibility for the older kernel. Let me know if I can
help with anything.

Thanks for your cooperation.