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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Mel Gorman' <mgorman@suse.de>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        David Hildenbrand <david@redhat.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 00/10] Fix confusion around MAX_ORDER
Thread-Topic: [PATCH 00/10] Fix confusion around MAX_ORDER
Thread-Index: AQHZXBOmxeBm0+nagESVZv8C8tAqRK8IeMpg
Date:   Thu, 23 Mar 2023 15:03:56 +0000
Message-ID: <54496a4d8b31499993aac50f2979f99a@AcuMS.aculab.com>
References: <20230315113133.11326-1-kirill.shutemov@linux.intel.com>
 <20230321163845.qpybxa5rlwclvko2@suse.de>
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From: Mel Gorman
> Sent: 21 March 2023 16:39
> 
> 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@suse.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.

How many of the places that use MAX_ORDER weren't touched?
Is it actually worth changing the name at the same time.
That will stop stable backport issues.

	David

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