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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 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[29]; MIME_TRACE(0.00)[0:+]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_TLS_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[oracle.com,redhat.com,google.com,cmpxchg.org,kernel.org,gmail.com,toxicpanda.com,huawei.com,weissschuh.net,infradead.org,suse.de,arm.com,csgroup.eu,vger.kernel.org,kvack.org]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; URIBL_BLOCKED(0.00)[imap1.dmz-prg2.suse.org:helo,suse.cz:email,suse.cz:mid]; R_RATELIMIT(0.00)[to_ip_from(RLqwhhqik4qyk5i1fk54co8f1o)] X-Spam-Flag: NO X-Spam-Score: -4.30 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