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Thu, 05 Nov 2026 08:23:59 -0800 (PST) Received: from localhost ([153.61.198.248]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8b097fe12f6sm2215796b3a.4.2026.11.05.08.23.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2026 08:23:59 -0800 (PST) Content-Type: text/plain; charset=UTF-8 Date: Thu, 05 Nov 2026 16:23:58 +0000 Message-Id: To: "David Hildenbrand (Arm)" , "Lorenzo Stoakes (ARM)" , "Zi Yan" , "Baolin Wang" , "Liam R. Howlett" , "Nico Pache" , "Ryan Roberts" , "Dev Jain" , "Barry Song" , "Lance Yang" , "Usama Arif" , "Kiryl Shutsemau" , "Andrew Morton" , "Peter Zijlstra" , "Ingo Molnar" , "Will Deacon" , "Boqun Feng" , "Waiman Long" , "Suren Baghdasaryan" , "Vlastimil Babka" , "Shakeel Butt" , "Yonghong Song" , "Daniel Borkmann" , "Andrii Nakryiko" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Martin KaFai Lau" , "Song Liu" , "Jiri Olsa" , "Emil Tsalapatis" , "Ihor Solodrai" Cc: , , Subject: Re: [PATCH 4/5] mm: add and use mmap_read_lock[_killable]_nosteal() on contention From: "Alexei Starovoitov" In-Reply-To: <3a77219e-39e5-4e98-8f88-6f90bccf69f0@kernel.org> References: <20261103-khugepaged-latency-fix-v1-0-a07ab16ac860@kernel.org> <20261103-khugepaged-latency-fix-v1-4-a07ab16ac860@kernel.org> <3a77219e-39e5-4e98-8f88-6f90bccf69f0@kernel.org> Content-Transfer-Encoding: 8bit X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Thu, Nov 05, 2026 at 02:16 AM David Hildenbrand (Arm) wrote: > On 11/3/26 09:27, Lorenzo Stoakes (ARM) wrote: >> With down_read[_killable]_nosteal() available, it becomes possible to >> release the mmap read lock in such a way that a queued write lock always >> takes precedence. >> >> Expose this to mm through two new wrappers - mmap_read_lock_nosteal() and >> mmap_read_lock_killable_nosteal(). >> >> Make use of this in scenarios where the mmap read lock is dropped >> explicitly for the purposes of relieving mmap_lock contention - the BPF >> task VMA iterator, and lock_next_vma_under_mmap_lock(), which is where >> /proc/$pid/smaps_rollup re-acquires the mmap lock after dropping it on >> contention and falling back from per-VMA locking. >> >> Signed-off-by: Lorenzo Stoakes (ARM) >> --- >> include/linux/mmap_lock.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ >> kernel/bpf/task_iter.c | 2 +- > > > I'd appreciate an ack from BPF folks and a confirmation that I could take this > through my tree :) Sure. Pls take it through your tree. No conflicts with bpf and bpf-next. Acked-by: Alexei Starovoitov