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AJvYcCURgDBYNqjOOhqL5k/aZOSL0XOXiRTbxpnQJ6LrP/LLtycUMTIBX60BrmB8LpbIKI3aQwhZrlvMgA==@kvack.org X-Gm-Message-State: AOJu0Ywp6fSlPHZVY76UJQdWJjFTKcbAoZNY+wys++DMNE9jaGxhoAcS FFdwcJJ2uvw6F6YlbQPmW/WqGN5KBY1h8eTtcd0MzWTKGWSUexHM8sKRQppz598OasQsXqqsewh R3Mmt+sQCgMvO0VKZpA/KSJP+3oQ= X-Google-Smtp-Source: AGHT+IGGmW/6/MnDDSXp8paozBcmrsqqmQRDfwgUCq1zX2ea1Ia9vKFqUtc48dIbbLDp6MvD9w2LMyx3qwM9Vn6jZTg= X-Received: by 2002:a17:90a:db8e:b0:2d8:e7db:9996 with SMTP id 98e67ed59e1d1-2e2c6333812mr1421771a91.13.1728502646371; Wed, 09 Oct 2024 12:37:26 -0700 (PDT) MIME-Version: 1.0 References: <20241001225207.2215639-1-andrii@kernel.org> <20241001225207.2215639-4-andrii@kernel.org> <20241003-lachs-handel-4f3a9f31403d@brauner> <20241004-holzweg-wahrgemacht-c1429b882127@brauner> <20241009-eisvogel-zugelangt-d211199df267@brauner> In-Reply-To: <20241009-eisvogel-zugelangt-d211199df267@brauner> From: Andrii Nakryiko Date: Wed, 9 Oct 2024 12:37:13 -0700 Message-ID: Subject: Re: [PATCH v2 tip/perf/core 3/5] fs: add back RCU-delayed freeing of FMODE_BACKING file To: Christian Brauner Cc: Andrii Nakryiko , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C58B0180021 X-Stat-Signature: hrd6wyc4kwx3bqnrgnbgcg8nz9rudiiz X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1728502647-836381 X-HE-Meta: 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 6yxS5fLZ +btlAo1J56bHzhqEKG4T/7R+deBlwJNR9P6iJiWbjlrTP3pxc1L+AjS7DY+DxPNRsCPGNJEl2b3VV+I9s9n5JU72hyEyPo1FbUYzC4lb7yRrDtIsvvhbyjo8bclCKtESzm+yjAOFwMZ2Gyfe+Q3tSJ9L/EJJn4DGqhkGz4J4P97Ubn8WXnh5XVZAvga6yzeXLtGFjU78sZsWW5C9IRbnXylVo0InAEC9Bw8ZTw6XJP7IYZHdc6WiDNCExlA/DAeaSIEiskzQqvBWf6vzZNj7xQBVyUp1GLKYSvsPCqeYpVorxmetc00KoW2fJFFI8PXXkYs/majUEXUyzUwdzU2ppOGpMIhtvXPe3l9T0L7+lDJ/vqBYJNmkS4CGNNwby5vr3kLFhw2o/dwc6k2QvYLpOIeut6PcGBMzvUQe/b6mKwe9SSKXQ6h9iOPjyipnopNa305tmSm2kaAg1+q8Ejhu+Sq8R5Q== 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 Wed, Oct 9, 2024 at 3:36=E2=80=AFAM Christian Brauner wrote: > > On Fri, Oct 04, 2024 at 12:58:00PM GMT, Andrii Nakryiko wrote: > > On Fri, Oct 4, 2024 at 1:01=E2=80=AFAM Christian Brauner wrote: > > > > > > 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_BACKI= NG > > > > > files to direct freeing as back then there were no use cases requ= iring > > > > > 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 freein= g > > > > > 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 wil= l > > > require me to switch FMODE_BACKING to a SLAB_TYPSAFE_BY_RCU cache. Th= at > > > shouldn't matter for your use-case though. > > > > Correct, we assume SLAB_TYPESAFE_BY_RCU semantics for the common case > > anyways. But hopefully my change won't cause major merge conflicts > > with your patch set. > > Please drop this patch and pull the following tag which adds > SLAB_TYPE_SAFE_BY_RCU protection for FMODE_BACKING files aligning them > with regular files lifetime (even though not needed). The branch the tag > is based on is stable and won't change anymore: > > git pull -S git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git tag= s/vfs-6.13.for-bpf.file Ok, will drop. It will on Peter to pull this tag into tip/perf/core, but I'll mention all this in the cover letter (and will pull locally for testing, of course). Thanks.