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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90e9eec7ffdsm18809156d6.25.2026.09.02.07.04.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Sep 2026 07:04:58 -0700 (PDT) Date: Wed, 2 Sep 2026 10:04:57 -0400 From: Gregory Price To: Liu Jing Cc: akpm@linux-foundation.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mempolicy: fix div-by-zero in alloc_pages_bulk_interleave Message-ID: References: <20260902090245.16411-1-liujing@cmss.chinamobile.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260902090245.16411-1-liujing@cmss.chinamobile.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8866520006 X-Stat-Signature: xwb7bd8ptra9g4e3bbdkqqsw8cagsmtp X-Rspam-User: X-HE-Tag: 1788357900-679157 X-HE-Meta: U2FsdGVkX18usQRaLrpKe/wRhlE6/GAXiaYLmZ/KpNZq9cyhPTwOtp9nlTxia7g9OH2qLyBAbDmYhGpDE6uIrMhgLLhz11DXqcN5YMBQozSbr49mSJX6CRyH3hMT8uzE8aoqiL5OKXOZ+EBd9Bcy2JTUyeKE/YBIUJvdj+MmntEfjy/tRtQ1o2XdjHNO1X6mge29V8cHOWo3U3Bydkg2mn5k45rf/y5ThK5vlFx2/WRCzpUgMipMJGozEZS50o7ojD1wX+6Qyzsbq9FbWaW8lSXT9YFsRNJ7bkvKJm9cE/1Wg1EzWaVyiHBpXP/qfRgPlaRGiy9Ox97EiWvwdep6JnxynUwIOFAklrFNqaalNH3dDj+TvmWABRgRoSUNbAMF7nHCSdTFAldikCHEn80nzWXgI0QXrWcCJsZmEJ0KGJ8xAELIXcUtXLjZamBAh/wBVjcRQxJmBy7oF8sm2CnCortIrI1vhBYjd6QIR5XHweOKc5NVNaLCH4kjSRVaMY7crxtHjfHwsZbkEd9U2lg5BjyaTRe5o4NdRT54fBq4H+DTxsYhQwSQ+9/0LJNMhaAFEOwFb0ziITy7aNCGVjFKgJX4S8K6NE6o2SOeV0a/3426ajwC8npxvf0QlfXkZ2am1GQOfYUx2eum04YtvYLZgQ1tmE+LeHIRywbBuzT2xX4KrhgG5l35vuiA82X0p1LWxXHdvAwf2CNOpuQ8UrWm9yblqzKcEEi7EXdeAicuj0bc5l+uxnVY4Lm23e9dqtu/6daswAKThfyETRrc9iTGxW2CV4SZuv53R6JEJrVmqSKgtP/qXGGnIU7TLzgtFApjYKJhonslKxR4mg/C4JTGHXNWFQtt6fR+27hIlRLFKrWX/M005iK5fn+DZV5JRQOhQwSP5fd6Nmo7tqxeKRVNZi+jBftIqaYoh8Ni+BnGS9i3NkjmKNPQG+QM2PmpmbrtP4dtvd9VMloUSOlAjeJ YPrV1qbF Hm2hcHAk1Snwm7N/QfEjog7CNhRD5DkAHVWP57ZtSfMHtRzNkY0g+4ch5WkXFpeyumu4qjuOZ042tO8WSQmN5DRGjiN3lFJ9md2hARBOT/DMpIvmRg35Aqb/8N5TM4t25deozjBedhEDKiCMLbAamkBXR2GzSANFKFkQClA/jyWcAJNPf5E2SqFW/AaXE0xAkd/hcU8z62VzSPwvXZMZG5d38v5Iey6YA4zxv3L/0nzOn0ZApnXq9TUf1KJxX04MX3AsE13KNY+N0vKtKwmWjQ/QuU+xeE9ePdxSK/KWzxzoouYOleB/dV9eb7Eall+gcQSBmNx8RMSvVYUzulRaOTCyjASfeFYvIwfdiC/3sghsvmvnwj4wMVrBUalVUQ2CAcwdupukJFVPoz3MV5P9FfzNKFSAlhe1VU/rXqN5pfK+xytY53J3NZmEuSlqMeDblKqOATbmCEhhLCZUbD9xpL4VxLyHtrsLMgGO2 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 02, 2026 at 05:02:45PM +0800, Liu Jing wrote: > In alloc_pages_bulk_interleave(), nodes_weight(pol->nodes) may return > 0 if all nodes in the policy mask have been offlined at runtime. The > subsequent division "nr_pages / nodes" triggers a divide-by-zero > panic. > now i'm positive this is LLM produced without understanding the component. A policy cannot have an empty nodemask, it can either 1) have no nodemask (default policy), or 2) be perceived as empty during a torn-read during a policy remap event If you are running LLMs to search for surface level bugs and try to hot-fix them without taking time to understand the underlying component, please at least: 1) tell us that 2) generate reproducers these "quick fixes" based on surface level observations are going to hide real bugs and just degrade the overall state of the system. > Add a zero check returning 0 (no pages allocated) when the nodemask > is empty, consistent with the guard in > alloc_pages_bulk_weighted_interleave(). > > Signed-off-by: Liu Jing > --- > mm/mempolicy.c | 3 +++ > 1 file changed, 3 insertion(+), 0 deletion(-) > > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -2600,6 +2600,9 @@ > unsigned long total_allocated = 0; > > nodes = nodes_weight(pol->nodes); > + if (!nodes) > + return 0; > + > nr_pages_per_node = nr_pages / nodes; > delta = nr_pages - nodes * nr_pages_per_node; > > > -- > 2.43.0 > >