linux-kernel - Re: [PATCH 1/2] mm: remove pfn_valid_within() and CONFIG_HOLES_IN

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Date:   Tue, 13 Jul 2021 11:51:46 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] mm: remove pfn_valid_within() and
 CONFIG_HOLES_IN_ZONE

On 13.07.21 10:00, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> After recent changes in freeing of the unused parts of the memory map and
> rework of pfn_valid() in arm and arm64 there are no architectures that can
> have holes in the memory map within a pageblock and so nothing can enable
> CONFIG_HOLES_IN_ZONE which guards non trivial implementation of
> pfn_valid_within().
> 
> With that, pfn_valid_within() is always hardwired to 1 and can be
> completely removed.
> 
> Remove calls to pfn_valid_within() and CONFIG_HOLES_IN_ZONE.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>

There is currently the discussion to increase MAX_ORDER, for example, to 
cover 1GiB instead of 4MiB on x86-64. This would mean that we could 
suddenly, again, have holes insides MAX_ORDER - 1 pages.

So I assume if we ever go down that path, we'll need something like this 
again.

For now, this looks like the right thing to do

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

-- 
Thanks,

David / dhildenb