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Wed, 8 Jan 2025 18:21:35 +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 0uMyKi/Cfme2FQAAD6G6ig (envelope-from ); Wed, 08 Jan 2025 18:21:35 +0000 Message-ID: <5bbc5573-4a10-4c89-bc69-6cf6117be915@suse.cz> Date: Wed, 8 Jan 2025 19:21:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 16/17] mm: make vma cache SLAB_TYPESAFE_BY_RCU Content-Language: en-US To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com References: <20241226170710.1159679-1-surenb@google.com> <20241226170710.1159679-17-surenb@google.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: z3mits5o7cqgsi1cifh8tu9r51q9cicc X-Rspamd-Queue-Id: AC602120034 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1736360497-504241 X-HE-Meta: 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 WOZDM8y9 cwh2ativviY79Mzxk69QLb7xX0I0KKnQ6SVGPtpfEZTLawBiZgSQ0ZyksT09uoTQs4Zbp3IdwEUngEeY/b6qXSuhhO/uzo4bJDP5U/YmLRJItBJqAqtU71HE8H4hE816C4ff7hLXwSgxwIyP9VdvwjcEnnHijZqtPIPqno5DKT/qvVv4uISDujU/vBpeZDZhy/txo/98pvuKIrN6wm312cpWvObV6Rw75NXX1hpP28cw6n+PDOPERvn7sShfQNbK70X6yZ3+Rnc2eXVgPM0pefkF07RHdt3cf7bE0CBjF1XQHAShfCtAsehYFWWfFW+HXrqEOM6tAhGycdZICJ17o1vUss5zzQLXtvjtXTikXFvIg91k= 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 12/26/24 18:07, Suren Baghdasaryan wrote: > To enable SLAB_TYPESAFE_BY_RCU for vma cache we need to ensure that > object reuse before RCU grace period is over will be detected by > lock_vma_under_rcu(). Current checks are sufficient as long as vma > is detached before it is freed. Implement this guarantee by calling > vma_ensure_detached() before vma is freed and make vm_area_cachep > SLAB_TYPESAFE_BY_RCU. This will facilitate vm_area_struct reuse and > will minimize the number of call_rcu() calls. > > Signed-off-by: Suren Baghdasaryan I've noticed vm_area_dup() went back to the approach of "we memcpy everything including vma_lock and detached (now the vm_refcnt) followed by a vma_init_lock(..., true) that does refcount_set(&vma->vm_refcnt, 0); Is that now safe against a racing lock_vma_under_rcu()? I think it's not?