linux-kernel - Re: [PATCH RESEND v1] mm/memory_hotplug: move debug_pagealloc_map_pages() into online_pages

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Message-ID: <0a745263-c6a2-40db-bb40-4d6129e7e66f@redhat.com>
Date: Wed, 4 Dec 2024 10:46:36 +0100
From: David Hildenbrand <david@...hat.com>
To: Oscar Salvador <osalvador@...e.de>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH RESEND v1] mm/memory_hotplug: move
 debug_pagealloc_map_pages() into online_pages_range()

On 03.12.24 16:28, Oscar Salvador wrote:
> On Tue, Dec 03, 2024 at 11:20:50AM +0100, David Hildenbrand wrote:
>> In the near future, we want to have a single way to handover PageOffline
>> pages to the buddy, whereby they could have:
>>
>> (a) Never been exposed to the buddy before: kept PageOffline when onlining
>>      the memory block.
>> (b) Been allocated from the buddy, for example using
>>      alloc_contig_range() to then be set PageOffline,
>>
>> Let's start by making generic_online_page() less special compared to
> 
> This got me confused for a moment. I'd have said "making
> __free_pages_core" less special? As that is where we were calling
> debug_pagealloc_map_pages() if the context  on the context.

Well, yes, but it's really generic_online_page()->__free_pages_core() 
that triggers this exact code only.

@Andrew, can you fix that up?

s/generic_online_page()/generic_online_page()->__free_pages_core()/

> 
>> ordinary page freeing (e.g., free_contig_range()), and perform the
>> debug_pagealloc_map_pages() call unconditionally, even when the online
>> callback might decide to keep the pages offline.
>>
>> All pages are already initialized with PageOffline, so nobody touches
>> them either way.
>>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Oscar Salvador <osalvador@...e.de>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
> 
> Acked-by: Oscar Salvador <osalvador@...e.de>

Thanks!

-- 
Cheers,

David / dhildenb