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b=1AbA6KGuVDMishj6sWpf+J0Yo8lpG41mjxhzMvhE4n/2vzd6pSMPclU1hqG7IBrEj wFwinYN1rKC+IPUWW4zmpuNC75nrU+ShelM6YUViiCar2Mr6EUTbekti8s1lj0Ibz5 lf05BQ8f4aek3KJ/cqOmZg1bvjb79gPZha2U3Ouc= Date: Mon, 14 Sep 2026 11:19:40 -0700 From: Andrew Morton To: "David Hildenbrand (Arm)" Cc: Kiryl Shutsemau , Lance Yang , ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev, ljs@kernel.org, surenb@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/1] mm/huge_memory: fix pgtable withdrawal for huge zero PMDs Message-Id: <20260914111940.f7e2c72eac4a2df97a646793@linux-foundation.org> In-Reply-To: References: <20260912234635.db50397364858aa15f58f4d7@linux-foundation.org> <20260913072312.52111-1-lance.yang@linux.dev> 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: rspam11 X-Rspamd-Queue-Id: B42AB40008 X-Stat-Signature: qz4c1195c5bxzf5aby3dsrkap5bk8rox X-Rspam-User: X-HE-Tag: 1789409981-486384 X-HE-Meta: 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 syLPHyrP NUl8yBLHp/ldYj5hfz1ges9Rto7Z/NxNrmQFSxOc2cyDeSKpSpwRUasHVpjUQNFM6sHV30dA11hNi0BNHB8kqSnpItS0W815puPaj/vn9C82EZ57cmH2nusUSphB+NVSaqJ1OWqAc5PY2jctKOaYp3IVlmNQnlqKGwgSAh2VKrgJWd9fMng7nQkP42yJcYXPKnx4GBEaARXvqoA597t1m3sxbjQGirHAsYSLpha+dzGTRB04Uj89GfdTb6JrdtWHsYA4POQlWdpT5JcJnrvvgbuNmepyIqEqiAni6QpEyZ8hAtynUmZwu6CvGZ7SMBpKhEG6ZvJqxIEB8WQ/mbwQ0Hj6J4A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 14 Sep 2026 16:29:00 +0200 "David Hildenbrand (Arm)" wrote: > On 9/14/26 12:59, Kiryl Shutsemau wrote: > > On Sun, Sep 13, 2026 at 03:23:12PM +0800, Lance Yang wrote: > >> > >> On Sat, Sep 12, 2026 at 11:46:35PM -0700, Andrew Morton wrote: > >>> > >>> > >>> That's the sort of thing we'd prefer to avoid. > >>> > >>> > >>> How real is this? Is there a reported-by:? Do you have a reproducer? > >> > >> Yes, I reproduced it on x86 with a small test module. It sets > >> VM_MIXEDMAP | VM_HUGEPAGE and calls vmf_insert_pfn_pmd() with > >> huge_zero_pfn, without touching the page tables directly. A full-PMD > >> munmap() crashes before the split series[1] as well. > > > > Ah. So there's no real bug upstream, right? > > Matches my understanding. Thanks. I'll remove cc:stable, move this into mm-unstable as a next-merge-window thing.