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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250225001023.1494422-3-hannes@cmpxchg.org> 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?