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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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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> 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