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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-Archived-By: MIME-Version: 1.0 X-Stat-Signature: th19hc5b9zr8n8pwj89qnufcuffo8ocm X-Rspamd-Queue-Id: 63752180006 X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793895841-806182 X-HE-Meta: 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 6SB6FAUb 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 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