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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> 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: <5e79bed1-598d-4e34-8f1e-87b6dba52bf8@suse.cz> 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