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Fri, 21 Feb 2025 09:25:27 -0800 (PST) MIME-Version: 1.0 References: <20250214-clarify-steal-v1-1-79dc5adf1b79@google.com> <20250214212647.GB233399@cmpxchg.org> <764394d9-592c-4d68-8910-67362dd8810a@suse.cz> <20250218203830.GA1264207@cmpxchg.org> In-Reply-To: <20250218203830.GA1264207@cmpxchg.org> From: Brendan Jackman Date: Fri, 21 Feb 2025 18:24:45 +0100 X-Gm-Features: AWEUYZmxRJng6dHgj-kLMXDQ1ghZUjfHWOkUm0eaqSXZt5jGmzay5c_NqxDW3NM Message-ID: Subject: Re: [PATCH] mm/page_alloc: Clarify some migratetype fallback code To: Johannes Weiner Cc: Vlastimil Babka , Andrew Morton , Mel Gorman , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yosry Ahmed Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: 0DCC514000E X-Stat-Signature: ihi7dozyx77diykknth334hub8jxukcf X-Rspamd-Server: rspam03 X-HE-Tag: 1740158728-427337 X-HE-Meta: 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 IV6GVcSJ 7U2P5MBHIxw8bplW2klRKHxq24ZN8p4PgUAhzuIeOz/5kPcHG6yzAaLTRdZfcBgNVVR5k6PZqV5I32tdJ85Ra6kLDC9fM7Aa6t7sItrOO0R8A3s/45rDghKDR+O6VpB8Jc46Pd41h21Enmdllh4mng1WwfKFf+ktzA+rxCWSGc7sCITteUiZV/77TN25apFK2vCoroxIFu6+kdVCS/v1qxc5bxEpDr/yWT9dTG8g/aRiiO0MMDvB23vhXvICdGr8DSI7YXXMMpXTM/+gm3SLpWIlpZ/KUQoPq63Jlk9yktnUx3KI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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 Tue, 18 Feb 2025 at 21:38, Johannes Weiner wrote: > > @@ -1930,7 +1929,7 @@ steal_suitable_fallback(struct zone *zone, struct page *page, /* * This can happen due to races and we want to prevent broken * highatomic accounting. */ > if (is_migrate_highatomic(block_type)) > - goto single_page; > + return NULL; Side question: when does this happen? Might have a spooky gap in my understanding here as I thought the only reason the pageblock typed was changed without the zone lock held was during memory hotplug.