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Shutemov" CC: Andrew Morton , Vlastimil Babka , David Hildenbrand , "linux-mm@kvack.org" , "linux-arch@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> In-Reply-To: <20230321163845.qpybxa5rlwclvko2@suse.de> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 6DAFF160026 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 6xqmzf4cu4zjsxhxsna7kdu178ywgzqk X-HE-Tag: 1679583842-909878 X-HE-Meta: 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 YN6WdyO/ +v1eprBJR5aCA9U0VfcegHRWNNiPwdjWWTU/G89i/M8WCX+bfk5CXRPfeBpXyEedJDtN8gQ43U1so9WmywLjqrD/HHuK73338GZwV+J7sxNRDizfofBNhDxh3obwO0Vl0e2DoVKa+QK/eNe8KIo7WRZabz1F6QbRyTii10Eu/F8Hp3slT7puliHNVCcn4LiH33tzD2Ri5tIzPHQ2gSekJpeJiEG6KeLNJJufV2tQE30F8c5IWk/+mKqNmSTFz8QHB3HUt4nvuww/wb/9S8Z6fP64EeBbKqjEupwrR1XP+M86AB9I= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Mel Gorman > Sent: 21 March 2023 16:39 >=20 > 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 ove= r > > 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. > > >=20 > Acked-by: Mel Gorman >=20 > 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. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)