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b=hx/9GIUzC6weS+i2CiFEMICfL1ntPu0oH8I8jR1NeERYr75bTL7qChXEoigeKp2ne zAR8l+J28+CW4+GVIzeTUElK8+2VgmjRs/u08bp3F/Drot6nkkJwQE95a7mfgaZxLS VIgdlVv7CV4hi54AFgLtqmqtAORnkqY81MKvtfcq6h2dFuPptpoS59mSb+/1KKlo1F W9Vsk9I9ocLvLgZ7gebPPPJ+0TWQXvM0sTSgyKIjwV5IpvouInDzKdiLqHsG+al2Ix JTOXX21aTqWZphIWkWiHU8bb4XueaelN8t6ALrnVwZoxRI7lms/cd4RuxtZmHcI9gm lKuDVuBEmxGZw== From: Pratyush Yadav To: Pasha Tatashin Cc: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.com, rppt@kernel.org, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, zhangguopeng@kylinos.cn, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, jgg@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com, hughd@google.com, skhawaja@google.com, chrisl@kernel.org, steven.sistare@oracle.com Subject: Re: [PATCH v4 14/30] liveupdate: luo_session: Add ioctls for file preservation and state management In-Reply-To: <20250929010321.3462457-15-pasha.tatashin@soleen.com> (Pasha Tatashin's message of "Mon, 29 Sep 2025 01:03:05 +0000") References: <20250929010321.3462457-1-pasha.tatashin@soleen.com> <20250929010321.3462457-15-pasha.tatashin@soleen.com> Date: Wed, 29 Oct 2025 20:07:31 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam05 X-Stat-Signature: 7n9hij8p9ku93jp8xp849u15fs3ubqza X-Rspam-User: X-Rspamd-Queue-Id: EA62B160011 X-HE-Tag: 1761764863-198386 X-HE-Meta: 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 zmaX74hT arOPtMW0yL0FuKU5XE45VEfeIH+NJ7bOCoCWg1Ia8DAUJq53T8cpzEX6cYFB2M1GFFkdezSQlY0Y3wPS882fxvG6k8hkHwjAi9vMKLTTlZ65CzCaOQWxSDQgwR+GVsIfrEIKej3ZJJBkfvvrfMJ2Rx1/B1y/c1KPTHpA65E569GfvvO4XPwfybw0Nghs9z5SLEknKod2AQ9APqYLyqKMvTQU3NlypwO/hVbNIl33MV65fS6QGOrZd0cD2mimsS2o9lvslNpr9ROeW/fAQRk19Fx5LPosAlGbpJbfzb7bTjalHl+o7bMe3OZEJjdvSgX+5EbuQxwDRxTsrIfyIOmAErpc1vLLLTZmvjDgK 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: Hi Pasha, On Mon, Sep 29 2025, Pasha Tatashin wrote: > Introducing the userspace interface and internal logic required to > manage the lifecycle of file descriptors within a session. Previously, a > session was merely a container; this change makes it a functional > management unit. > > The following capabilities are added: > > A new set of ioctl commands are added, which operate on the file > descriptor returned by CREATE_SESSION. This allows userspace to: > - LIVEUPDATE_SESSION_PRESERVE_FD: Add a file descriptor to a session > to be preserved across the live update. > - LIVEUPDATE_SESSION_UNPRESERVE_FD: Remove a previously added file > descriptor from the session. > - LIVEUPDATE_SESSION_RESTORE_FD: Retrieve a preserved file in the > new kernel using its unique token. > > A state machine for each individual session, distinct from the global > LUO state. This enables more granular control, allowing userspace to > prepare or freeze specific sessions independently. This is managed via: > - LIVEUPDATE_SESSION_SET_EVENT: An ioctl to send PREPARE, FREEZE, > CANCEL, or FINISH events to a single session. > - LIVEUPDATE_SESSION_GET_STATE: An ioctl to query the current state > of a single session. > > The global subsystem callbacks (luo_session_prepare, luo_session_freeze) > are updated to iterate through all existing sessions. They now trigger > the appropriate per-session state transitions for any sessions that > haven't already been transitioned individually by userspace. > > The session's .release handler is enhanced to be state-aware. When a > session's file descriptor is closed, it now correctly cancels or > finishes the session based on its current state before freeing all > associated file resources, preventing resource leaks. > > Signed-off-by: Pasha Tatashin [...] > +/** > + * struct liveupdate_session_get_state - ioctl(LIVEUPDATE_SESSION_GET_STATE) > + * @size: Input; sizeof(struct liveupdate_session_get_state) > + * @incoming: Input; If 1, query the state of a restored file from the incoming > + * (previous kernel's) set. If 0, query a file being prepared for > + * preservation in the current set. Spotted this when working on updating my test suite for LUO. This seems to be a leftover from a previous version. I don't see it being used anywhere in the code. Also, I think the model we should have is to only allow new sessions in normal state. Currently luo_session_create() allows creating a new session in updated state. This would end up mixing sessions from a previous boot and sessions from current boot. I don't really see a reason for that and I think the userspace should first call finish before starting new serialization. Keeps things simpler. > + * @reserved: Must be zero. > + * @state: Output; The live update state of this FD. > + * > + * Query the current live update state of a specific preserved file descriptor. > + * > + * - %LIVEUPDATE_STATE_NORMAL: Default state > + * - %LIVEUPDATE_STATE_PREPARED: Prepare callback has been performed on this FD. > + * - %LIVEUPDATE_STATE_FROZEN: Freeze callback ahs been performed on this FD. > + * - %LIVEUPDATE_STATE_UPDATED: The system has successfully rebooted into the > + * new kernel. > + * > + * See the definition of &enum liveupdate_state for more details on each state. > + * > + * Return: 0 on success, negative error code on failure. > + */ > +struct liveupdate_session_get_state { > + __u32 size; > + __u8 incoming; > + __u8 reserved[3]; > + __u32 state; > +}; > + > +#define LIVEUPDATE_SESSION_GET_STATE \ > + _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_STATE) [...] -- Regards, Pratyush Yadav