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[79.224.246.120]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-464f527d6cdsm7187695e9.12.2025.09.17.11.34.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Sep 2025 11:34:12 -0700 (PDT) Message-ID: <322fd5d2-d7f4-40d8-8a06-6e7c5e9ef180@redhat.com> Date: Wed, 17 Sep 2025 20:34:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/7] mm: add assertion for VMA count limit To: Kalesh Singh Cc: akpm@linux-foundation.org, minchan@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, pfalcato@suse.de, kernel-team@android.com, android-mm@google.com, Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Jann Horn , Shuah Khan , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20250915163838.631445-1-kaleshsingh@google.com> <20250915163838.631445-7-kaleshsingh@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 1AFE4160003 X-Stat-Signature: y1a5sjgfwwjpt9zs99397tahoriii4rj X-HE-Tag: 1758134056-974600 X-HE-Meta: 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 IzmbNzMD XdRyiKBEjkrRqMFTF5/v5FLIclY91qTqsAMYTpwtHZIXVIrz8BGKzLX3C53QYWLBkmycFVBF1HYB9HBfmrOqYOa6ZGxWaMxJbYeJEhmSbutdJRCZCRlItDjjZaJYhevlIuV+FarZAxLxoqITs49TzXto1FX0vtz04mP+zh5fBlxqQEqkJmbh2WUUiZVoK1Yb17FUcIN+6jZ/cemhBfhK98eLjDvJki1KGofbkKzHubCXyDXHzNDCSnm++cME/+07MqMqP3gRI5TPr7SherjlDF2Jn0DB79pVK3c9rlrkcC2v6vuQ2qSpnUAG/LkniRPQhOSVKj9MR8SV35eiF/UsXx25UOsIwPGzj3SrRpDDtP9+wFWXrR9TAbwf9qrJ2NngIRrqovTedgAKqBt/tizikmLkg6aO+HSlfH4At 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: >> Can't that fire when changing the max count from user space at just the >> wrong time? > > You are right: technically it's possible if it was raised between the > time of checking and when the new VMA is added. > >> >> I assume we'll have to tolerated that and might just want to drop this >> patch from the series. >> > > It is compiled out in !CONFIG_VM_DEBUG builds, would we still want to drop it? Due to the racy nature I think any kinds of assertions would be wrong. Without any such races possible I would agree that the checks would be nice to have. -- Cheers David / dhildenb