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[2003:cb:c70b:b400:e20a:6d03:7ac8:f97d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438b31898ebsm68535605e9.2.2025.01.23.09.14.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Jan 2025 09:14:52 -0800 (PST) Message-ID: <7a4f8c38-13a1-4a28-b7ce-ad3bb983dd69@redhat.com> Date: Thu, 23 Jan 2025 18:14:50 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 4/4] userfaultfd: use per-vma locks in userfaultfd operations To: Lorenzo Stoakes , Barry Song <21cnbao@gmail.com> Cc: lokeshgidra@google.com, Liam.Howlett@oracle.com, aarcange@redhat.com, akpm@linux-foundation.org, axelrasmussen@google.com, bgeffon@google.com, jannh@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ngeoffray@google.com, peterx@redhat.com, rppt@kernel.org, ryan.roberts@arm.com, selinux@vger.kernel.org, surenb@google.com, timmurray@google.com, willy@infradead.org References: <20240215182756.3448972-5-lokeshgidra@google.com> <20250123041427.1987-1-21cnbao@gmail.com> <6aee73c6-09aa-4c2a-a28e-af9532f3f66c@lucifer.local> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit >> >> ┌────────────┐TASK_SIZE >> │ │ >> │ │ >> │ │mmap VOLATILE >> ┼────────────┤ >> │ │ >> │ │ >> │ │ >> │ │ >> │ │default mmap >> │ │ >> │ │ >> └────────────┘ >> >> VMAs in the volatile region are assigned their own volatile_mmap_lock, >> which is independent of the mmap_lock for the non-volatile region. >> Additionally, we ensure that no single VMA spans the boundary between >> the volatile and non-volatile regions. This separation prevents the >> frequent modifications of a small number of volatile VMAs from blocking >> other operations on a large number of non-volatile VMAs. > > I think really overall this will be solving one can of worms by introducing > another can of very large worms in space :P but perhaps I am missing > details here. Fully agreed; not a big fan :) -- Cheers, David / dhildenb