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b=PS38d2F+HD6yJ+cCZ27VfTyu/Xb5ZNzr80MqBwuo05yeFYAXUJdvjE5nUUkXYcFFD +5183EI4m7vKpS3ZZwa7ynwmCHyhTwcz+iEuPcYXMSWAvc3cub34I6kp/Cnbduib2k O2om8Jm3FT/iufyjmHEZqTttkvC6e+bBJbYB2icy6vI5KYYdvLq6XlDk1bKyZZ9tZh roMVdrRyxyw38iwxO2aGZ2XNKX9DBFV8xK31IMNliK86ajR/C3rW3abM/BOELVQbfR C0M8uOI3syHk24+OYOUanJp+f96ijtCAJSGZ55L2Ur8Kc8x9HzduLTQ+LWWXzdhMpq ipF5HIEmgZ2pA== From: Pratyush Yadav To: Zhu Yanjun Cc: Pasha Tatashin , akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, pratyush@kernel.org, rdunlap@infradead.org, rppt@kernel.org, tj@kernel.org Subject: Re: [PATCH v9 1/9] kho: make debugfs interface optional In-Reply-To: <442fa82e-16ef-4bde-84eb-743450222468@linux.dev> (Zhu Yanjun's message of "Sun, 9 Nov 2025 16:20:56 -0800") References: <20251101142325.1326536-1-pasha.tatashin@soleen.com> <20251101142325.1326536-2-pasha.tatashin@soleen.com> <029090cf-9a4d-4f79-b857-04c3ada83323@linux.dev> <442fa82e-16ef-4bde-84eb-743450222468@linux.dev> Date: Mon, 10 Nov 2025 14:16:37 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 2CD614000A X-Stat-Signature: b4souenhyc6pi75hnff94i3apms7rqja X-Rspam-User: X-HE-Tag: 1762780601-523355 X-HE-Meta: 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 YKwtW4XU /1FEA3kJVAx2HJbcOCKevYMMLXhWZ4+lJ8Su+YbHiwvSw4xCVZPheyn0uXsZEyJAYoEJuMOCx7Ahrb0IGiQPE5pRsKnQc9rQTVfW3zuV96SnYqOuoUHkel5uaKIPhlb26d2E5UwAm/FZKJ8a7KKEtDs9P9st4J77m5goc3VPGW3Gu5OizimyfDJ0DHMXZkLrNMIb8vKnE8ik31EEJcacIDXGTbZjcAnlnu7MMb+ilFAJJ2W7nPcU2C9JWFOgs3eiL11CvyMb/DtNr4Ev14pGX2rwDf87Va/pwRhXH6JEFmiZmoT+yEVkqYsxhug== 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 Sun, Nov 09 2025, Zhu Yanjun wrote: > =E5=9C=A8 2025/11/8 10:13, Pasha Tatashin =E5=86=99=E9=81=93: >> On Fri, Nov 7, 2025 at 6:36=E2=80=AFPM Yanjun.Zhu = wrote: >>> >>> On 11/7/25 4:02 AM, Pasha Tatashin wrote: >>>> On Fri, Nov 7, 2025 at 7:00=E2=80=AFAM Pasha Tatashin wrote: >>>>>> Hi, Pasha >>>>>> >>>>>> In our previous discussion, we talked about counting the number of t= imes >>>>>> the kernel is rebooted via kexec. At that time, you suggested adding= a >>>>>> variable in debugfs to keep track of this count. >>>>>> However, since debugfs is now optional, where would be an appropriate >>>>>> place to store this variable? >>>>> It is an optional config and can still be enabled if the live update >>>>> reboot number value needs to be accessed through debugfs. However, >>>>> given that debugfs does not guarantee a stable interface, tooling >>>>> should not be built to require these interfaces. >>>>> >>>>> In the WIP LUO [1] I have, I pr_info() the live update number during >>>>> boot and also store it in the incoming LUO FDT tree, which can also be >>>>> accessed through this optional debugfs interface. >>>>> >>>>> The pr_info message appears like this during boot: >>>>> [ 0.000000] luo: Retrieved live update data, liveupdate number: 17 >>>>> >>>>> Pasha >>>> Forgot to add link to WIP LUOv5: >>>> [1] https://github.com/soleen/linux/tree/luo/v5rc04 >>> >>> Thanks a lot. I=E2=80=99ve carefully read this commit: >>> https://github.com/soleen/linux/commit/60205b9a95c319dc9965f119303a1d83= f0ff08fa. >>> >>> To be honest, I=E2=80=99d like to run some tests with who/luo, includin= g the >>> selftest for kho/luo. Could you please share the steps with me? >>> >>> If the testing steps have already been documented somewhere, could you >>> please share the link? >> Currently the test performs in-kernel tests for FLB data, it creates a >> number of FLB for every registered LUO file-handler, which at the >> moment is only memfd. >> >> It works together with any of the kexec based live update tests. In >> v5, I introduce two tests: >> luo_kexec_simple >> luo_multi_session >> >> For example, with luo_multi_session: > > Hi, Pasha > > I enabled "CONFIG_LIVEUPDATE=3Dy" > > # ./luo_multi_session > 1..0 # SKIP Failed to open /dev/liveupdate. Is the luo module loaded? > > # ls /dev/liveupdate > ls: cannot access '/dev/liveupdate': No such file or directory > > # grep "LIVEUPDATE" -inrHI /boot/config-`uname -r` > /boot/config-next-20251107-luo+:349:CONFIG_LIVEUPDATE=3Dy > /boot/config-next-20251107-luo+:11985:CONFIG_LIVEUPDATE_TEST=3Dy > > I made tests on FC42. But /dev/liveupdate is missing. You need to add liveupdate=3D1 to your kernel cmdline to enable LUO and get /dev/liveupdate. Pasha, your LUO series doesn't add the liveupdate parameter to kernel-parameters.txt. I think it should be done in the next version to this parameter is discoverable. --=20 Regards, Pratyush Yadav