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Sun, 14 Dec 2025 08:06:11 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4f1bd70c2a7sm78168641cf.33.2025.12.14.08.06.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 14 Dec 2025 08:06:10 -0800 (PST) Date: Sun, 14 Dec 2025 11:06:06 -0500 From: Johannes Weiner To: Vlastimil Babka Cc: Alexander Gordeev , Andrew Morton , Marc Hartmayer , linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/page_alloc: change all pageblocks migrate type on coalescing Message-ID: <20251214160606.GA905277@cmpxchg.org> References: <20251212151457.3898073Add-agordeev@linux.ibm.com> <5e79bed1-598d-4e34-8f1e-87b6dba52bf8@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5e79bed1-598d-4e34-8f1e-87b6dba52bf8@suse.cz> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2703D12001E X-Stat-Signature: ujzb6kfqckzfzb8a4tdiq337maixwi4d X-Rspam-User: X-HE-Tag: 1765728372-960698 X-HE-Meta: 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 rLcTi0Ad 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Fri, Dec 12, 2025 at 04:46:46PM +0100, Vlastimil Babka wrote: > On 12/12/25 16:14, Alexander Gordeev wrote: > > When a page is freed it coalesces with a buddy into a higher > > order page while possible. When the buddy page migrate type > > differs, it is expected to be updated to match the one of the > > page being freed. > > > > However, only the first pageblock of the buddy page is updated, > > while the rest of the pageblocks are left unchanged. > > > > That causes warnings in later expand() and other code paths > > (like below), since an inconsistency between migration type > > of the list containing the page and the page-owned pageblocks > > migration types is introduced. Absolutely right, and the fix makes sense to me. Thanks! > Hm I guess we haven't seen this before because it's common that > pageblock_order is just one below MAX_ORDER so we're only merging two > pageblocks. But your arch/config must be different to expose it. In any case > LGTM, thanks. +1 > Acked-by: Vlastimil Babka Acked-by: Johannes Weiner The warning makes the issue loud, but your patch is arguably fixing an earlier commit that introduces type updates during merges. How about: Fixes: e6cf9e1c4cde ("mm: page_alloc: fix up block types when merging compatible blocks") Cc: stable@kernel.org