linux-kernel - Re: [PATCH 0/3 v2] fs/proc: extend the PAGEMAP

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Message-ID: <CAEWA0a6KdODW2hD3G0PO+yUFC4rZCaTGU_orC3CAuHXRXoqREQ@mail.gmail.com>
Date: Mon, 31 Mar 2025 09:12:14 -0700
From: Andrei Vagin <avagin@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org, 
	David Hildenbrand <david@...hat.com>, Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>, 
	criu@...ts.linux.dev
Subject: Re: [PATCH 0/3 v2] fs/proc: extend the PAGEMAP_SCAN ioctl to report
 guard regions

On Mon, Mar 31, 2025 at 4:26 AM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> 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.