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Fri, 21 Feb 2025 09:33:04 -0800 (PST) Date: Fri, 21 Feb 2025 12:33:03 -0500 From: Johannes Weiner To: Brendan Jackman Cc: Vlastimil Babka , Andrew Morton , Mel Gorman , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: Re: [PATCH] mm/page_alloc: Clarify some migratetype fallback code Message-ID: <20250221173303.GA1316314@cmpxchg.org> References: <20250214-clarify-steal-v1-1-79dc5adf1b79@google.com> <20250214212647.GB233399@cmpxchg.org> <764394d9-592c-4d68-8910-67362dd8810a@suse.cz> <20250218203830.GA1264207@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: On Fri, Feb 21, 2025 at 06:24:45PM +0100, Brendan Jackman wrote: > 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. Good job catching that. I don't think they are needed anymore after the hygiene patches. I had proposed removing them as a follow-up, but never got around to it: https://lore.kernel.org/linux-mm/20230912150320.GB3228@cmpxchg.org/ I'll send a proper patch.