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AFNElJ/kNWzBDgxT1svQJht7ZhUmtaET5hYOrgZVxwJheJWGAuG+TtN8bHFxtJ2Bqg4/e9TdnozuitTcwg==@kvack.org X-Gm-Message-State: AOJu0YzNvdZmusePDggE3F29NCj4K9Zz3tO2uTGQHVhN6BSBECHRw7WI OLt85IhmNaVw4NYkM3rp9b6WF6MrjIf9ATaRaGmOWxcXY8UrrQW7yz1LJZHSgsg6Y2FTOpdV9T/ //IGK6A== X-Received: from dlbur21-n2.prod.google.com ([2002:a05:7022:ea55:20b0:12d:c516:f51]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7022:11c:b0:12b:ec67:3523 with SMTP id a92af1059eb24-12c73f726eamr19447643c88.9.1777184841793; Sat, 25 Apr 2026 23:27:21 -0700 (PDT) Date: Sat, 25 Apr 2026 23:27:15 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.54.0.545.g6539524ca2-goog Message-ID: <20260426062718.1238437-1-surenb@google.com> Subject: [PATCH v2 0/3] use vma locks for proc/pid/{smaps|numa_maps} reads From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, david@redhat.com, willy@infradead.org, jannh@google.com, paulmck@kernel.org, pfalcato@suse.de, shuah@kernel.org, hsukrut3@gmail.com, richard.weiyang@gmail.com, reddybalavignesh9979@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, surenb@google.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 794B580004 X-Rspam-User: X-Stat-Signature: pgtifibr7k8segfiqj3g9yisxi77gpoq X-HE-Tag: 1777184843-120043 X-HE-Meta: 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 fFvZQtpf 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Use per-vma locks when reading /proc/pid/smaps and /proc/pid/numa_maps similar to /proc/pid/maps to reduce contention on central mmap_lock. One major difference between maps and smaps/numa_maps reading is that the latter executes page table walk which can't be done under RCU due to a possibility of sleeping. Therefore we drop RCU read lock before this walk while keeping the VMA locked. After the walk we retake RCU read lock, reset VMA iterator and proceed with the next VMA. The last two patches extend /proc/pid/maps test to cover /proc/pid/smaps reading during concurrent address space modification. Changes since v1[1] - moved drop_rcu earlied in smap_gather_stats to avoid sleeping under RCU lock in shmem_swap_usage(), per Sashiko - skip page walks for gate VMA in show_numa_map(), per Sashiko - introduced parse_vma_line() and copy_line() helper functions to ensure input string passed to sscanf() is always NUL-terminated, per Sashiko - used FIXTURE_VARIANT to run both maps and smaps tests in a single test run, per Liam R. Howlett Applies over mm-unstable. [1] https://lore.kernel.org/all/20260424070234.190145-1-surenb@google.com/ Suren Baghdasaryan (3): fs/proc/task_mmu: read proc/pid/{smaps|numa_maps} under per-vma lock selftests/proc: ensure the test is performed at the right page boundary selftests/proc: add /proc/pid/smaps tearing tests fs/proc/task_mmu.c | 195 +++++++++--- tools/testing/selftests/proc/proc-maps-race.c | 293 ++++++++++++++---- 2 files changed, 387 insertions(+), 101 deletions(-) base-commit: 761e9fad336afb6fe2cd488c7bd522e2783064fc -- 2.54.0.545.g6539524ca2-goog