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

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Message-ID: <7263e869-d733-44f4-bd2b-9c6f89202909@lucifer.local>
Date: Mon, 31 Mar 2025 12:26:40 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrei Vagin <avagin@...gle.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 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 :)
>
> Andrei Vagin (3):
>   fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions
>   tools headers UAPI: Sync linux/fs.h with the kernel sources
>   selftests/mm: add PAGEMAP_SCAN guard region test
>
>  Documentation/admin-guide/mm/pagemap.rst   |  1 +
>  fs/proc/task_mmu.c                         | 17 ++++---
>  include/uapi/linux/fs.h                    |  1 +
>  tools/include/uapi/linux/fs.h              | 19 +++++++-
>  tools/testing/selftests/mm/guard-regions.c | 57 ++++++++++++++++++++++
>  5 files changed, 87 insertions(+), 8 deletions(-)
>
> --
> 2.49.0.rc1.451.g8f38331e32-goog
>