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

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Message-ID: <54496a4d8b31499993aac50f2979f99a@AcuMS.aculab.com>
Date:   Thu, 23 Mar 2023 15:03:56 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Mel Gorman' <mgorman@...e.de>,
        "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-mm@...ck.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 00/10] Fix confusion around MAX_ORDER

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@...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.

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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