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b=BNoPTNH2mY6hAGlBSJMX1nCiPi/BoGcEcnnfFq6+h+wDjw1G0y3hs+ebQAtAiOELD yJgwrrd+Ds0GpFEn8jauqMs8Ehpf+VQDtoj4/b6jGVizI7Ad9DgH0pv2uuAGGif266 OEHVIx4AvTC1axwF8GssWq1nVxDxxYHCzUnB9V7JIgH/pNrP9bqVUhtnJW/Ac4lRbX fIDxYERC1b21qEqhiEx+KpoEDgSx9BuagIKuqrxTN4GJvtB90vSRNFLEQgrldSHxxm LsT5zfRiRhFmJ0HPZLYF4fdDqnqwgIEqAH7zIVU2uyHIUGvEyYpQ3IINiIuWcUgelT o6ASz9eiq/Z3w== Message-ID: Date: Tue, 27 Oct 2026 14:37:01 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/6] mm/page_alloc: don't undo another isolation in alloc_contig_range To: "Gregory Price (Meta)" , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, osalvador@suse.de, muchun.song@linux.dev, iamjoonsoo.kim@lge.com, anshuman.khandual@arm.com, stable@vger.kernel.org References: <20261027042204.3741307-1-gourry@gourry.net> <20261027042204.3741307-5-gourry@gourry.net> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6EFDC100007 X-Stat-Signature: pdotffsqzqexbbpuw18oxpn6f8thjxwd X-Rspam-User: X-Spam-Status: No, score=-12.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793108231-537711 X-HE-Meta: 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 Xuk5bcwk kqz0RdwYY3C9epcbr+o1wsRTRBS+YYC6J2UjeWXK6Djy39s9E/2g2gwcNJxb44FfCtcIKu5r6qnfH5LbRQDCEUA7SuJ4bNlEl9c1ZKMxlF/VfME7LbEIsg6SNNYR+5fQkuQFnp45dUZz/ZObjj+RME1LznvJrNNF8WgGfpKO3zXDV5iMaee0p6EqSGVe/dVQ8oud5oxCHcgBQcL55lgTIVVE/ZxNhVUgAy8pvt2BYYhwYkkZ1YW+In0cqVexJrr/iVccoQXRSYykUClt5OrYtnJ00dnIsCx4Fp5vnFhf/boKohXhkE+tO81X7TTwbwm96v04v0ePfnN9l5UvkFXVgouUhOCVegvEigHjMq4sjPTMQgoM81EEAEDxoECqBnHthyGVLOpveyu/gw0t3C/KlKPEzPbyBEcc7r+9/lj9EE2K9gidofxx71YjFLeQie0bkLL/NOUeS4I8Fyi4jcpfbr7620w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/27/26 05:22, Gregory Price (Meta) wrote: > An alloc_contig_range() that overlaps a block going offline can leave > the offline spinning until it gets a signal, holding the device hotplug > lock. When isolation fails, alloc_contig_frozen_range() undoes it over > the whole range, clearing the offline's MIGRATE_ISOLATE too: > > CPU 1 (offline_pages) CPU 2 (alloc_contig_range) > start_isolate_page_range() > blocks are MIGRATE_ISOLATE > start_isolate_page_range() > -EBUSY on CPU 1's blocks > undo_isolate_page_range() > blocks are MIGRATE_MOVABLE > test_pages_isolated() > never succeeds again > > start_isolate_page_range() fails only on a block someone else isolated, > after undoing its own, so this undo only ever clears another caller's. > Return directly, as before alloc_contig_range() went pageblock granular. > > With offline_pages() parked after isolating a DIMM block and a 1G > hugetlb allocation made over it, the offline on base still loops 30s > later in 4 of 4 runs: > > offline_pages+0x5b2/0x1570 > memory_subsys_offline+0x17e/0x470 > device_offline+0x250/0x340 > state_store+0x88/0x110 > > With this patch the allocation still fails, and the offline completes in > 3 of 3 runs. > > Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity") > Cc: stable@vger.kernel.org > Signed-off-by: Gregory Price (Meta) > --- We have an existing AI fix for that as well already handled by Vlasta. I think we'll have to establish some model of "ask David first before posting" because otherwise we just create duplicate work for everyone. -- Cheers, David