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b=uPAQ/fIAE/QAAjeYGXWo1YTo3Y0qqWBhc/8Y/n0CMFHT2N1RT8KtWDpQStMeiGlkt rbq2a1fnLhcuWcxo3xc3K2rQ0DOJ4IUq8kQQyNc1baSXmayh3uPGajSN6/K9CjE5HX 7UjKViGzApNDpCSTdeI0WcidECgzLJgnwAEW959FuxTuCr26DAKT/MyLXbMvygh08X rAB+T91BbTMa5I9efZZvLvdc8O/T6kmDhnb7zrYqN4kTjejmW90sIyfPoCVI+3ZJJ/ C6AFH41VHQIBZzj241AyYWqiQStA2hNt6zLdbAqhNOa5qrUIFB9hb9ismRdq+xvV7O 7zs6JklKtCP+g== Date: Fri, 4 Oct 2024 10:01:35 +0200 From: Christian Brauner To: Andrii Nakryiko Cc: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, mjguzik@gmail.com, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, mingo@kernel.org, Amir Goldstein Subject: Re: [PATCH v2 tip/perf/core 3/5] fs: add back RCU-delayed freeing of FMODE_BACKING file Message-ID: <20241004-holzweg-wahrgemacht-c1429b882127@brauner> References: <20241001225207.2215639-1-andrii@kernel.org> <20241001225207.2215639-4-andrii@kernel.org> <20241003-lachs-handel-4f3a9f31403d@brauner> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241003-lachs-handel-4f3a9f31403d@brauner> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A22C016000D X-Stat-Signature: iamt6bhjrnebjuiczub6kktu7nqc6a4e X-Rspam-User: X-HE-Tag: 1728028902-469719 X-HE-Meta: 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 2epbgSfC DyEMiNKDWYVIbvibKE1KJhwu9PaiUDBj0E2AbUjGkgxOjC0kfpvjYb3OhATeRwynYLnLudj7Pmnbm6lIGJUq9254q6BhtOlbyJsM3TLfNFCYh9ewBpDR5r7D9u1zAi7g4XTUIj4EJsw3RLcYLXKfgmbQubDy9f5Pu9N+iVqSHGwCBI8svqwCMAU8uHG299mObCqR3RPBHTKFAqRgV4D1lYPizW9U/iHAft/5SB1toHC8ui9qMzMItZJ70tR3JV5jeihJTlIkIF3BFFSwnt3Ev7wNlG/aPHQRgURgKlGxUSdpETCPR2wXm6uHGMfwDI50mjzTQ7dOR3Il7sjkN5bJYe7da68gUJVDsGt/9Hg8wvGZZG3WGHmuYLssSPYDrz0nNt/6ByzgukuwhF1nSItTyK1Q4saK0vv2q19pTNuRCK5MqwhQ= 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 Thu, Oct 03, 2024 at 11:13:54AM GMT, Christian Brauner wrote: > On Tue, Oct 01, 2024 at 03:52:05PM GMT, Andrii Nakryiko wrote: > > 6cf41fcfe099 ("backing file: free directly") switched FMODE_BACKING > > files to direct freeing as back then there were no use cases requiring > > RCU protected access to such files. > > > > Now, with speculative lockless VMA-to-uprobe lookup logic, we do need to > > have a guarantee that struct file memory is not going to be freed from > > under us during speculative check. So add back RCU-delayed freeing > > logic. > > > > We use headless kfree_rcu_mightsleep() variant, as file_free() is only > > called for FMODE_BACKING files in might_sleep() context. > > > > Suggested-by: Suren Baghdasaryan > > Cc: Christian Brauner > > Cc: Amir Goldstein > > Signed-off-by: Andrii Nakryiko > > --- > > Reviewed-by: Christian Brauner Fwiw, I have another patch series for files that I'm testing that will require me to switch FMODE_BACKING to a SLAB_TYPSAFE_BY_RCU cache. That shouldn't matter for your use-case though.