linux-kernel - Re: [PATCH] arch/x86: Do not explicitly clear Reserved flag in free

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Date: Mon, 27 May 2024 09:46:05 +0200
From: David Hildenbrand <david@...hat.com>
To: Oscar Salvador <osalvador@...e.de>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH] arch/x86: Do not explicitly clear Reserved flag in
 free_pagetable

Am 27.05.24 um 06:45 schrieb Oscar Salvador:
> In free_pagetable() we use the non-atomic version for clearing the
> PageReserved bit from the page.
> free_pagetable() will either call free_reserved_page() or
> put_page_bootmem(), which will eventually end up calling
> free_serverd_page(), and in there we already clear the PageReserved flag.
> 
> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> ---
> This has been like this since commit ae9aae9eda2d ("memory-hotplug: common APIs to
> support page tables hot-remove"), so I might be missing something obvious, but
> I cannot explain why we would need that __ClearPageReserved upfront, when
> free_reserved_pages() already does that for us.

Especially, we only call it on the first page (in case we'd have order>0).

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb