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Fri, 28 Aug 2026 01:49:40 +0000 X-Mizu-Trace-ID: a00269d0398ad22b X-Migadu-Flow: FLOW_OUT Message-ID: <45518155-3a29-48c4-89bf-40d81c2ef6d6@linux.dev> Date: Fri, 28 Aug 2026 09:49:34 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm/mglru: fix ineffective memory protection for non-kswapd reclaim To: =?UTF-8?Q?Michal_Koutn=C3=BD?= Cc: sashiko-reviews@lists.linux.dev, tj@kernel.org, hannes@cmpxchg.org, "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" References: <20260826133054.88529-1-ridong.chen@linux.dev> <20260826134733.051941F000E9@smtp.kernel.org> <0c606cf9-2b5a-4549-8ab1-0be619487412@linux.dev> From: Ridong Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: w6xmuf1utwecw56wa4kwfc1f6q9ezf4e X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 5847B180004 X-Rspam-User: X-HE-Tag: 1787881795-290966 X-HE-Meta: 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 +OPNSPHT PE4SjkOS2wo7jOqCMexdwOle2jZPPrNleVFKojXw+zdAQLra7sGkXhbXSq6F390m7idKlZDhNBVHlb7nwkc8ekSaIkXBcigArsFKouuc/robM5FFAJjlWSZvboiP7erLnUYRR+t1hhHjIGTRsnbzTGeFoJyRyZYWvqhYvnaM4xXhkdhwI+ufah18yitgzgoPGaJsqG8DCV8MzgoToIrZ8K8q5vKVTnsnuAmZj0XbSXdWArr3Hxg1wmKQjw9dTk5/rKipy2fzUVhzAqeQA29ktps7vLK8k+0FM8hrAOVQ6iN3PGNO5uzccDFQwWSBYB6eF09cTE/CjL5IBMDTwLoViEiN0ZA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/27/2026 5:26 PM, Michal Koutný wrote: > Hi Ridong. > > On Thu, Aug 27, 2026 at 09:29:13AM +0800, Ridong Chen wrote: >> On 8/26/2026 9:47 PM, sashiko-bot@kernel.org wrote: >>> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: >>> >>> Pre-existing issues: >>> - [High] Integer overflow in `effective_protection()` calculations on systems with >= 16TB RAM. >>> -- >>> >> >> Thanks for the careful analysis. You're right that this is pre-existing in >> effective_protection() and not introduced by this patch. >> >> I'm not sure it's worth fixing in practice, though — the overflow requires >> systems with >= 16TB of RAM, which I've never encountered >> myself. So I'd rather not fold a fix for it into this patch. >> >> I'd like to hear the maintainers' thoughts on whether this is worth >> addressing separately. > > Machines with >=16 TiB aren't completely out of reach [1]. Then > configuring such protections to attain the overflow is another > condition, so I'd consider this a nice to have but not a > pressing fixup (separately, with thorough review of occurences where > total page counts/bytes might get multiplied). > > HTH, > Michal > > [1] E.g. https://aws.amazon.com/ec2/instance-types/u7i/ Thanks Michal, It's worth fixing now, I'll send a separate patch to address it. -- Best regards Ridong