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Tsirkin" , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Minchan Kim , Vlastimil Babka , linuxppc-dev@lists.ozlabs.org, devicetree@vger.kernel.org, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH v1 2/2] mm: enforce pageblock_order < MAX_ORDER Date: Mon, 14 Feb 2022 13:05:16 -0500 X-Mailer: MailMate (1.14r5869) Message-ID: In-Reply-To: <20220214174132.219303-3-david@redhat.com> References: <20220214174132.219303-1-david@redhat.com> <20220214174132.219303-3-david@redhat.com> Content-Type: multipart/signed; boundary="=_MailMate_52C0766F-C3EF-48B0-B542-8703D600332F_="; micalg=pgp-sha512; protocol="application/pgp-signature" X-ClientProxiedBy: MN2PR08CA0017.namprd08.prod.outlook.com (2603:10b6:208:239::22) To MN2PR12MB3823.namprd12.prod.outlook.com (2603:10b6:208:168::26) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 1bedac8c-7c7e-45d7-c932-08d9efe48f51 X-MS-TrafficTypeDiagnostic: DM6PR12MB3803:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; 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dkim=pass header.d=Nvidia.com header.s=selector2 header.b="saj6/OYr"; dmarc=pass (policy=reject) header.from=nvidia.com; spf=none (imf09.hostedemail.com: domain of ziy@nvidia.com has no SPF policy when checking 40.107.237.64) smtp.mailfrom=ziy@nvidia.com X-HE-Tag: 1644861920-519847 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: --=_MailMate_52C0766F-C3EF-48B0-B542-8703D600332F_= Content-Type: text/plain On 14 Feb 2022, at 12:41, David Hildenbrand wrote: > Some places in the kernel don't really expect pageblock_order >= > MAX_ORDER, and it looks like this is only possible in corner cases: > > 1) CONFIG_DEFERRED_STRUCT_PAGE_INIT we'll end up freeing pageblock_order > pages via __free_pages_core(), which cannot possibly work. > > 2) find_zone_movable_pfns_for_nodes() will roundup the ZONE_MOVABLE > start PFN to MAX_ORDER_NR_PAGES. Consequently with a bigger > pageblock_order, we could have a single pageblock partially managed by > two zones. > > 3) compaction code runs into __fragmentation_index() with order > >= MAX_ORDER, when checking WARN_ON_ONCE(order >= MAX_ORDER). [1] > > 4) mm/page_reporting.c won't be reporting any pages with default > page_reporting_order == pageblock_order, as we'll be skipping the > reporting loop inside page_reporting_process_zone(). > > 5) __rmqueue_fallback() will never be able to steal with > ALLOC_NOFRAGMENT. > > pageblock_order >= MAX_ORDER is weird either way: it's a pure > optimization for making alloc_contig_range(), as used for allcoation of > gigantic pages, a little more reliable to succeed. However, if there is > demand for somewhat reliable allocation of gigantic pages, affected setups > should be using CMA or boottime allocations instead. > > So let's make sure that pageblock_order < MAX_ORDER and simplify. > > [1] https://lkml.kernel.org/r/87r189a2ks.fsf@linux.ibm.com > > Signed-off-by: David Hildenbrand > --- > drivers/virtio/virtio_mem.c | 9 +++------ > include/linux/cma.h | 3 +-- > include/linux/pageblock-flags.h | 7 +++++-- > mm/Kconfig | 3 +++ > mm/page_alloc.c | 32 ++++++++------------------------ > 5 files changed, 20 insertions(+), 34 deletions(-) LGTM. Thanks. Reviewed-by: Zi Yan -- Best Regards, Yan, Zi --=_MailMate_52C0766F-C3EF-48B0-B542-8703D600332F_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQJDBAEBCgAtFiEEh7yFAW3gwjwQ4C9anbJR82th+ooFAmIKmd0PHHppeUBudmlk aWEuY29tAAoJEJ2yUfNrYfqKTQsP/3r4RQN9p3Adw1F3G0GqaM6LEe8yaHYCK2oz FOut1UAs6kTQh71FZ2jwLKIDt8oc2XQF0+2YecquqI+x8l1oWrymuElKoAjO1Qiy /xIbLrmnV4GzVFrd802gbQpG/xiIp4GYZMXewwtuJtjyqmF2OL0xyObG61Lp6ZML u5WUJ7TzWTmwT0zNeGbkZ4Q1twhzE2kQWFRhEV/rwwFwi3Eua3FANtS+ADQXaCZ7 kM57KetvtaWlt7TrHn6camKeC4EDrNVb9LKDj2chGvvfIxl6kMuxgWBKbFtQHF9z CwkaTZNuAAqWbrVe+6mgKtE+9mtNDpkptgp0zGCuoMnzEm77FiudQoms2gsYDZ9w KhT9Semmg7KuoIoxa0qWTc7GiB7/y4YIKOB0hPPQYnlpduau4KkysanRoQxsQ5mf oxCyvS4mu5quPzY0qsvVdMtE81K6tmpzDxYu27Qaj6sRnPy3ct/5b2gakoBoYOk5 wHRXXe+0L0eFfg1C74KFTMJ4j7aWZzKK91CAxuVV9AoiNgu0qeaRebzbgxAPagos 9dp1q/Wt3P/In2kdBK1yIT4TafT6qKLk+9MgpjKRyXYWKJO17x04YbnlGethojzF YrJR8b2ib9ZsuHye1KLoqKx0LFArqXNapwygekbcjN2wp/nyQuWbNGmzzmsLctrm H3AT2+DP =Pxl+ -----END PGP SIGNATURE----- --=_MailMate_52C0766F-C3EF-48B0-B542-8703D600332F_=--