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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 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 Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7135020018 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: aewdb5k5cekqta8uuwppx3nw5rtz8udx X-HE-Tag: 1737652500-420461 X-HE-Meta: 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 AlG8JXrK bsiNhTtxCCdzK1vhWJ8ocIviImg1+cTSPdictApxhVBAU1xw4DF/edtdazm1tKLFaYWnEE294g9/EYXvbWQ8MZdQIUfQEtHbsYUB2MzvLF0998pXCrr3Uiv74gU1gfN4DNwX8qS6r1P/74UY7NpsniUgknanhc7tQzKuBqu+247uJzhGftgg3yBDAseBptiEaxlXZLKh3j4TFeTjZQN2c55aubijMtO9ufeH5FNis2E7h3QLPNWYdMPE/vg5QgfeVFR9HVuR/d/wxdIy9UwdXx91vMsVZKwwEzJOVvOQml2WvlP2vCRhwh+CZwEkwQ4Urv10pvDufWU3KqtsnAZyoEv+RswrVaAXpsld9o1KNRRX6q89a3nR61haOlf9FJlW6bBRLxW3kb2dX7SWPm/IeALIwNSRR+N2Vjvkyq13O9sKSGnY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000080, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> >> ┌────────────┐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