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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) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 89D0C180004 X-Stat-Signature: snewjpasw8yh4tac336u8jsy6soph4jp X-Rspam-User: X-HE-Tag: 1784851371-364540 X-HE-Meta: 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 CyxmhUH6 26BFffzRt6wXPkTunEZinZ+t+DMQ1+6UU/NuGXnnP5UXHripWnyK0XVZifBOneHjob6EzndtmYinxciYP+TP13aunGtrSCx+U+9edwKCn9X4kGZaW2fs0cKtx/+NEI77IUqVFyzZbN3528xwRY1EJo2tHXUOs6qEX0mhhEvvFYs7TTRWQFAtQTZOrFzoDi3YsMCvWJwqI+T60qTEs4Cp4NzytaIRAQCefhOK29SRsw+yMeAYet2KBoEUPvg7imLSP5kO+S3tVahktnNOeDNVeabvJBDQWZC7ir97H2xxONMFOokYjlmyvlsLbTdPCQ9GvBt6F Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.