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b=YGfsAtH1SaRWz5ZO2owf+AkYYxzeP93z2XE/fSNKttVgS945LQ7hxEThQWjVAeD3k Q82S3BBNOiKQZwJf4H2+dK8Vi8mnOORfNPUEZ/NYDaEtpqdgkR4myBymvWubCyOOw2 t4Lg95AkpnFMhCBAh1rzy2u5MbB5XHpWuioxe/X6/HXwAz+jDD6jefLa004wOgcUvl PqBgJp/xai9T7pDgapyEkyAsZ5sXdijOwTIcXjPeEPYI2vnNbUkmAb/AZ9kC0Zl2W9 fmHT5gNeXSqlDvAtmnLM9itByKMehuMunzfOsaXHx9lkQYCI7LWryRdT9Af13fONCz BVSraE1KkCSmA== Date: Thu, 3 Oct 2024 11:13:46 +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: <20241003-lachs-handel-4f3a9f31403d@brauner> References: <20241001225207.2215639-1-andrii@kernel.org> <20241001225207.2215639-4-andrii@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241001225207.2215639-4-andrii@kernel.org> X-Stat-Signature: 7g99mdsiithb163dgp65mqu3p3bh3jia X-Rspamd-Queue-Id: C4513C0019 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1727946834-363974 X-HE-Meta: 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 /qtqGR7e fr/NpbIG9o0CfUaeemSWHQeqrcY6ECD3YUGTnzqGImbwSerd8so4JaM4N+iGsCaVAT6EFCePLi8RSKC9u4Rxb+8B0hVmBisVEkjzH/ot1+D18uNWL/e+jYT3nVRe8djte5iHhiYey4MXPiAqbu2vLvBi6tW2IXpymFdBjjdM7F4gMqQBbkY/BFViJQLjG1FNM2gFJ322GfGSARZGP5tsg6tz1tl/+T/PVBN73gqKycxVrJdpyjV3zLX28j+ZvwQrza26QmN7rgtS7jB4066WuIvJo8RO0z0GM23zAF3YC5MgxJDGqFRMoVgb5XX3ogBYxj0ncCJ5UZcqlR43hqHqNuhcKDAkX73kVoPjtgrs4R/7pnuRWBZwNyFPNTZmDXYdW0mtL3PzzFAwoopUx6ESJwOZm3EvrlX7h+I8qrT8/709DgXfMvroy4LvBmM8BfqpXjc9W 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 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