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[35.199.49.16]) by smtp.gmail.com with ESMTPSA id ada2fe7eead31-7d3023838a9sm4907083137.7.2026.11.11.13.13.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Nov 2026 13:13:30 -0800 (PST) X-Archived-By: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 11 Nov 2026 16:13:29 -0500 Message-Id: Subject: Re: [PATCH v5 5/6] liveupdate: Add LIVEUPDATE_SESSION_FREEZE ioctl to freeze sessions early From: "Pasha Tatashin" To: "Mike Rapoport" , "Pasha Tatashin" Cc: , , , , , , , , , , , , X-Mailer: aerc 0.22.0-39-g5d7784875be2 References: <20261105050053.3063001-1-pasha.tatashin@soleen.com> <20261105050053.3063001-6-pasha.tatashin@soleen.com> <179439592041.425130.6098227055493441109.b4-review@b4> In-Reply-To: <179439592041.425130.6098227055493441109.b4-review@b4> X-Stat-Signature: nqy1ztzojtj4eni51194swbr8jc1e341 X-Rspamd-Queue-Id: 2F26920004 X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1794431612-782797 X-HE-Meta: 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 xvWE8Tm/ oSp/fhy2Ynx6yiQnQLQQzKKnRAGOxRl6zf5zEJOaGoRmW36M6DqkpPx+9zY+49A6CQ8QzlNdpRpMo6l0RTgrh9qVDUBhMbfBsq2viN6t7d9QHYVmFAbN4KRt26DYcQ4NLxS6n7hEyWIGphXWlVMAul7Ib03KHplkf1qC36lj7jK4pSLLdCKyoKtNl1pqwBbnZMQfeqnTRb5XAR8xzX+z/4By7mH4kuEGYX9u0vwCXollmkl1eikpDh8HNTWN9QNwq7j+VfLRMtaEKJWVzQAg+3dylZEqKRKJl5CmI6rZ2r/dWsKRu8VvUi/t5BkzXmpEH2R5O1Ps1BPTusrJog6JzAdEbvs7nXGjaVT9xX1v2uJP8dsJWSM+N2ggtJzRNnQ6UfclZWgVeUB+mawhihVLsWT0q5w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed Nov 11, 2026 at 6:18 AM EST, Mike Rapoport wrote: > Hi, > >> Currently, LUO sessions are frozen automatically only inside the >> reboot(LINUX_REBOOT_CMD_KEXEC) pathway, where luo_session_serialize() >> iterates through all outgoing sessions under global write locks and >> freezes them serially during shutdown. On hosts running multiple >> workloads that quiesce one by one ahead of kexec, userspace needs an >> explicit per-session freeze point so each session can capture final file >> state under its per-session mutex as soon as its workload pauses. >>=20 >> Introduce LIVEUPDATE_SESSION_FREEZE on session FDs to freeze an outgoing >> session early. The ioctl runs .freeze() across all preserved files in >> the session and serializes their metadata. Once frozen, no additional >> files can be added to the session, and subsequent freeze calls return >> -EBUSY. Freeze is only valid on outgoing sessions and returns -EINVAL on >> incoming ones. >>=20 >> By default (flags =3D=3D 0), session lifetime remains bound to the sessi= on >> FD: the session stays frozen while the FD remains open, and closing the >> session FD before reboot (for example, to abort the session or on >> process exit/crash) unfreezes it via .unfreeze(), unpreserves its files, >> and reclaims all resources. During kexec, already-frozen sessions skip >> the late auto-freeze and are published into the outgoing KHO subtree. >>=20 >> With LIVEUPDATE_SESSION_FREEZE_COMMIT set in >> struct liveupdate_session_freeze.flags, the frozen session is committed: >> it and its FLB dependencies are immediately inserted into the outgoing >> KHO subtree via luo_session_publish_one(), and the session survives >> close() with full ownership retained by LUO until reboot. Once >> committed, closing the session FD (or another session failing to freeze >> during reboot) never unfreezes or unpreserves the session, allowing >> processes to hand off preserved state and exit prior to kexec. >>=20 >> Update the uAPI and core LUO documentation to describe session freeze >> and commit semantics. > > Please teach your LLM to use shorter paragraphs, focus on why and don't > list every implementation detail, but only important ones. The first paragraph explains exactly why; however, I agree that it needs=20 to be more concise. I will address your comments in v6. Thanks! --=20 Pasha