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Fri, 8 Aug 2025 17:46:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 6GkKOto3lmjUaAAAD6G6ig (envelope-from ); Fri, 08 Aug 2025 17:46:02 +0000 Message-ID: <2a53f01c-db74-4298-bb9e-36b770e4fcd0@suse.cz> Date: Fri, 8 Aug 2025 19:46:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/3] fs/proc/task_mmu: execute PROCMAP_QUERY ioctl under per-vma locks Content-Language: en-US To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, peterx@redhat.com, jannh@google.com, hannes@cmpxchg.org, mhocko@kernel.org, paulmck@kernel.org, shuah@kernel.org, adobriyan@gmail.com, brauner@kernel.org, josef@toxicpanda.com, yebin10@huawei.com, linux@weissschuh.net, willy@infradead.org, osalvador@suse.de, andrii@kernel.org, ryan.roberts@arm.com, christophe.leroy@csgroup.eu, tjmercier@google.com, kaleshsingh@google.com, aha310510@gmail.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, SeongJae Park References: <20250808152850.2580887-1-surenb@google.com> <20250808152850.2580887-4-surenb@google.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4D23940002 X-Stat-Signature: ha659ecyicqqq1dd3o63mpzpoirj7xwb X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1754675165-158558 X-HE-Meta: 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 OsBew96a x+YCQtLBnHvB6f+T4cuknGKYvg1WqDpMaWlcW3EC54FK9q7fUH0GaHrb21wSv1oC9OevyfAfQ3IXNI/frZ0s+C4ufgXpL4Z1BQyRDcgjCHG+CN9Cnm28aL1EglD7mqdbtTZ4d0Xn5A/QaTFOY4vIEmtaRjk/z65iYCe9yINcGxw96yfkTTSiwdrWy8YWkaL4OUeeMCc74SmSOtHZizMQcRDhDRGroyZSOY0/jF0TO72ST1waISvItLrGj0GGbqPx+ymSuVerd8MVwSL1aCZHBxDZbnkq2wEh2jH5mxayfzZYV7WXJ3Scig2GvXTn3xW8HWH7DN7k6hBKByJZVlA0M83qAjnMQSKvro+c59/izoD1ph7LEXOu3hkzWkTuqK1oIbDrL 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: On 8/8/25 17:28, Suren Baghdasaryan wrote: > Utilize per-vma locks to stabilize vma after lookup without taking > mmap_lock during PROCMAP_QUERY ioctl execution. If vma lock is > contended, we fall back to mmap_lock but take it only momentarily > to lock the vma and release the mmap_lock. In a very unlikely case > of vm_refcnt overflow, this fall back path will fail and ioctl is > done under mmap_lock protection. > > This change is designed to reduce mmap_lock contention and prevent > PROCMAP_QUERY ioctl calls from blocking address space updates. > > Signed-off-by: Suren Baghdasaryan > Acked-by: SeongJae Park Reviewed-by: Vlastimil Babka