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[35.205.27.248]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-439b036756csm140784665e9.31.2025.02.25.05.43.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2025 05:43:39 -0800 (PST) Date: Tue, 25 Feb 2025 13:43:35 +0000 From: Brendan Jackman To: Johannes Weiner Cc: Andrew Morton , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] mm: page_alloc: remove remnants of unlocked migratetype updates Message-ID: References: <20250225001023.1494422-1-hannes@cmpxchg.org> <20250225001023.1494422-3-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250225001023.1494422-3-hannes@cmpxchg.org> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 3D11A4000D X-Stat-Signature: x181ukcgxn3arfff3a5ybasxxrfrneoz X-HE-Tag: 1740491020-480688 X-HE-Meta: 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 X9P2TZpA 1O130xRDuD/Tc3TP2hdsKvH3dkOxkD1mIceaAmhSbZ4L5/r5lJNeQoMcvGK5Rhpe8rna9r+qzQUULZa7Gg4Y9CInxDVw7gTstopKaoVEYJ19j/U+SSPR7vSAPR4sZvGDDXN/0BRxrTIOHo6bqtCb2u1EVwcGIxX91ybUKPe/ECMQ0xp1e5ofIEbzggg3SYoIsDpgqHYONk5xKVHepqplzS60jUaUckLGqgbQA4R8jo/SXqrRJpQegXo14d/BoJlZ8TLR7IbuYaniZymU9nbWejbAPVhNMw1yaOvJEpQMG5LGOCYcBr8N6JAQMNrjJNlUwYftDeou8zmFrk050LYK46W0VZ5AcIyNx/NkGi/d+ds0v3s7jgYn3KP3ykNtngD2t5AGjTkoYyFmBweihMJSlJGDNlA1sx5epmPPOg2BYmVG8inwQLhG+cHK6M6ikTzQdRJuAeqq4ojVyc1M= X-Bogosity: Ham, tests=bogofilter, spamicity=0.003367, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Feb 24, 2025 at 07:08:25PM -0500, Johannes Weiner wrote: > The freelist hygiene patches made migratetype accesses fully protected > under the zone->lock. Remove remnants of handling the race conditions > that existed before from the MIGRATE_HIGHATOMIC code. > > Signed-off-by: Johannes Weiner Aside from my WARN bikeshedding, which isn't really about this patch anyway: Reviewed-by: Brendan Jackman > - if (is_migrate_highatomic(mt)) { > - unsigned long size; > - /* > - * It should never happen but changes to > - * locking could inadvertently allow a per-cpu > - * drain to add pages to MIGRATE_HIGHATOMIC > - * while unreserving so be safe and watch for > - * underflows. > - */ > - size = max(pageblock_nr_pages, 1UL << order); > - size = min(size, zone->nr_reserved_highatomic); > - zone->nr_reserved_highatomic -= size; > - } > + size = max(pageblock_nr_pages, 1UL << order); > + size = min(size, zone->nr_reserved_highatomic); > + zone->nr_reserved_highatomic -= size; Now that the locking is a bit cleaner, would it make sense to add a [VM_]WARN_ON[_ONCE] for underflow?