linux-kernel - Re: [PATCH v4 01/14] mm/mm_init: rename init_reserved_page to init_deferred

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Message-ID: <20250220083601.4p6ehmfhyvs5q5io@master>
Date: Thu, 20 Feb 2025 08:36:01 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: Wei Yang <richard.weiyang@...il.com>, linux-kernel@...r.kernel.org,
	Alexander Graf <graf@...zon.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Anthony Yznaga <anthony.yznaga@...cle.com>,
	Arnd Bergmann <arnd@...db.de>, Ashish Kalra <ashish.kalra@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Borislav Petkov <bp@...en8.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Eric Biederman <ebiederm@...ssion.com>,
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	Krzysztof Kozlowski <krzk@...nel.org>,
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	linux-doc@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH v4 01/14] mm/mm_init: rename init_reserved_page to
 init_deferred_page

On Wed, Feb 19, 2025 at 09:13:22AM +0200, Mike Rapoport wrote:
>Hi,
>
>On Tue, Feb 18, 2025 at 02:59:04PM +0000, Wei Yang wrote:
>> On Thu, Feb 06, 2025 at 03:27:41PM +0200, Mike Rapoport wrote:
>> >From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
>> >
>> >When CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, init_reserved_page()
>> >function performs initialization of a struct page that would have been
>> >deferred normally.
>> >
>> >Rename it to init_deferred_page() to better reflect what the function does.
>> 
>> Would it be confused with deferred_init_pages()?
>
>Why? It initializes a single page, deferred_init_pages() initializes many.
>

See below.

>> And it still calls __init_reserved_page_zone(), even we __SetPageReserved()
>> after it. Current logic looks not clear.
>
>There's no __init_reserved_page_zone(). Currently init_reserved_page()
>detects the zone of the page and calls __init_single_page(), so essentially
>it initializes one struct page.
>
>And we __SetPageReserved() in reserve_bootmem_region() after call to
>init_reseved_page() because pages there are indeed reserved.
> 

Hmm... I am not sure we are looking at the same code. I take a look at current
mm-unstable, this patch set is not included.  So I am looking at previous
version with this last commit:

  8bf30f9d23eb 2025-02-06 Documentation: KHO: add memblock bindings

Here is what I see for init_deferred_page()'s definition:

init_deferred_page()
  __init_deferred_page()
    __init_reserved_page_zone()   <--- I do see this function, it is removed?
      __init_single_page()

What I want to say is __init_deferred_page() calls
__init_reserved_page_zone(). This sounds imply a deferred page is always
reserved page. But we know it is not.  deferred_init_pages() initialize the
pages are not reserved one. Or we want to have this context in
__init_deferred_page()?

>-- 
>Sincerely yours,
>Mike.

-- 
Wei Yang
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