linux-kernel - Re: [PATCH 00/10] Fix confusion around MAX

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Date:   Tue, 21 Mar 2023 16:38:45 +0000
From:   Mel Gorman <mgorman@...e.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/10] Fix confusion around MAX_ORDER

On Wed, Mar 15, 2023 at 02:31:23PM +0300, Kirill A. Shutemov wrote:
> MAX_ORDER currently defined as number of orders page allocator supports:
> user can ask buddy allocator for page order between 0 and MAX_ORDER-1.
> 
> This definition is counter-intuitive and lead to number of bugs all over
> the kernel.
> 
> Fix the bugs and then change the definition of MAX_ORDER to be
> inclusive: the range of orders user can ask from buddy allocator is
> 0..MAX_ORDER now.
> 

Acked-by: Mel Gorman <mgorman@...e.de>

Overall looks sane other than the fixups that need to be added as
flagged by LKP. There is a mild risk for stable backports that reference
MAX_ORDER but that's the responsibilty of who is doing the backport.
There is a mild risk of muscle memory adding off-by-one errors for new
code using MAX_ORDER but it's low.

-- 
Mel Gorman
SUSE Labs