linux-kernel - Re: [PATCH v3 0/4] mm: introduce snapshot

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Message-ID: <226304ff-e8f3-4ba0-812c-f1356d4d8de1@amd.com>
Date: Mon, 14 Jul 2025 19:25:32 +0530
From: Shivank Garg <shivankg@....com>
To: Luiz Capitulino <luizcap@...hat.com>, david@...hat.com,
 willy@...radead.org, akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, sj@...nel.org,
 harry.yoo@...cle.com
Subject: Re: [PATCH v3 0/4] mm: introduce snapshot_page()



On 7/14/2025 6:46 PM, Luiz Capitulino wrote:
> Hi,
> 
> The series introduction will follow the changelog. This is against bc9ff192a6c9 .
> 
> Changelog
> =========
> 
> v2 -> v3
>   - Small snapshot_page() refactor to simplify and fix stack-out-of-bugs bug
>     reported by Harry Yoo
>   - Use clear_compound_head() in snapshot_page() (Shivank)
>   - Read head pointer from ps->page_snapshot() for tail page case (Shivank)
>   - Improve comments and macro name in snapshot_page() (David)
> 
> v1 -> v2
>   - Include is_huge_zero_pfn() patch and use it (David)
>   - Move free page detection to snapshot_page() (David)
>   - Changelog improvements (Shivank)
>   - Added Acked-bys
> 
> RFC -> v1
>   - Include <linux/page_idle.h> to avoid build error on sh arch
> 
> Introduction
> ============
> 
> This series introduces snapshot_page(), a helper function that can be used
> to create a snapshot of a struct page and its associated struct folio.
> 
> This function is intended to help callers with a consistent view of a
> a folio while reducing the chance of encountering partially updated or
> inconsistent state, such as during folio splitting which could lead to
> crashes and BUG_ON()s being triggered.
> 
> David Hildenbrand (1):
>   mm/memory: introduce is_huge_zero_pfn() and use it in
>     vm_normal_page_pmd()
> 
> Luiz Capitulino (3):
>   mm/util: introduce snapshot_page()
>   proc: kpagecount: use snapshot_page()
>   fs: stable_page_flags(): use snapshot_page()
> 
>  fs/proc/page.c          | 50 +++++++++++++++-----------
>  include/linux/huge_mm.h | 12 ++++++-
>  include/linux/mm.h      | 19 ++++++++++
>  mm/debug.c              | 42 +++-------------------
>  mm/memory.c             |  2 +-
>  mm/util.c               | 79 +++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 144 insertions(+), 60 deletions(-)
> 

The changes look good to me.
Thanks for addressing the feedback.

Reviewed-by: Shivank Garg <shivankg@....com>