From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E19AD1DA57; Fri, 24 Jul 2026 00:02:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784851372; cv=none; b=S2YDg2O7Julc4EZ9qnuEIOaLxbT5QGRcixFKgqZHb02Ais7QbcZ8FpUwa7afcWBPFOksUz9ZWg/d873JRuOoYu2rhJCTx8qLodixNThYOmOuyXwGIb5jrCcGrc2WSNmx1k/ofWSvnj7RzJ3aB4kXwJaS5TyjmAuKgJvEAHdosvA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784851372; c=relaxed/simple; bh=+jeKp8UReakMpv5M7ur1K2WG96E+Z+HftIGiPY2KAJ0=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=fWgw76IrCBufoQ3/k2YSXLyv0UihEaSOc8ChZBMJNDL/UDFUHJKSNiKIbFNy43NjYz6VKaRUNCTARljZdKB9TEiEIhfFnU6BGPYcNoaL+zuKyFReUXedaDaM1G389NjQouPoGDnMi+9FU0Nmg8ZVd+FeJEw8NGua+D02IZe7h84= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=LBcwVAU0; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="LBcwVAU0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CDB1A1F000E9; Fri, 24 Jul 2026 00:02:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1784851370; bh=c9E04AFsCJ/VZ9edKXAtGVUUjcTIxBBUMYLvzGUzl5U=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=LBcwVAU0Maz8s9W9L1HgHkU9+APYMXK0mWzYaa/ZRGIlgln0kLS27D8ggbEblmF0J 0QQWnHVI50v4BzgZvGwtfJYCc5Uucl1Dvq2uYu1l7uZZHkYOGJ0psgix6YPjCd+FQR zOxtuggw3kInBwUd7ZsZ5A6Eo9N68yK2Xhp92CqQ= Date: Thu, 23 Jul 2026 17:02:49 -0700 From: Andrew Morton To: "Vlastimil Babka (SUSE)" Cc: Johannes Weiner , Greg Kroah-Hartman , Sasha Levin , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Zi Yan , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Shakeel Butt , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 4/4] mm: page_alloc: fix non-movable reclaim storm in defrag_mode Message-Id: <20260723170249.98d83bd68698fff2629391c4@linux-foundation.org> In-Reply-To: <00bb7fd0-998b-49f0-9941-cc4d796a8751@kernel.org> References: <20260722150006.3848560-1-hannes@cmpxchg.org> <20260722150006.3848560-5-hannes@cmpxchg.org> <20260722162207.31a2c491ffaf36d1e8948c14@linux-foundation.org> <67e1219e-9d47-4a30-a8dd-fdcf03229f58@kernel.org> <00bb7fd0-998b-49f0-9941-cc4d796a8751@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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-Transfer-Encoding: 7bit On Thu, 23 Jul 2026 16:17:51 +0200 "Vlastimil Babka (SUSE)" wrote: > > 2/4 actually came after 4/4 during development. Without it, compaction > > cannot make sufficient forward progress on the promoted non-movable > > requests. So it is a hard functional requirement. > > So that's the tricky part then. If it's a hard functional requirement for > 4/4 and yet leaving it out results in no conflicts when applying 3/4 and 4/4 > (as it indeed seems so, based on my local test), then it's quite possible > stable folks will figure out themselves they need 3/4 as a stable-dep-off: > 4/4 but won't backport 2/4, unless you act quickly enough on their mails. > > > Whether it deserves an independent Fixes: depends on how many > > GFP_KERNEL pageblock_order requests we have :-) I'm guessing not many. > > I don't know how else to indicate it though. It's kind of a co-fix with 4/4? > > >> > (An alternative would be to put cc:stable on all four patches. That's > >> > a bit abusive but we do it rarely). > >> > >> I don't think it's necessary, the stable team are quite capable of figuring > >> out the deps and backporting them with a Stable-dep-off: tag. IIRC the > >> "fake" tagging is discouraged? Maybe they can clarify. > > > > Yes, I *think* it should work with tagging just 4/4. > > > > It won't apply cleanly or build without 3/4. So I'd assume if that > > dependency is lost, the automated backport will bounce and I can send > > a backport series by hand. > > The way I see if often happen is that Greg sends a mail that it bounced and > soon after Sasha replies with fixed up version/series. Which could very > easily be 3/4 + 4/4 without 2/4. My brain hurts. I'll include Fixes: e3aa7df331bc ("mm: page_alloc: defrag_mode") Cc: in all four patches.