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[35.245.167.64]) by smtp.gmail.com with ESMTPSA id ada2fe7eead31-7d3023543casm3548860137.5.2026.11.11.03.45.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Nov 2026 03:45:14 -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 06:45:13 -0500 Message-Id: Cc: , , , , , , , , , , , , Subject: Re: [PATCH v5 0/6] liveupdate: Add LIVEUPDATE_SESSION_FREEZE ioctl From: "Pasha Tatashin" To: "Mike Rapoport" , "Pasha Tatashin" X-Mailer: aerc 0.22.0-39-g5d7784875be2 References: <20261105050053.3063001-1-pasha.tatashin@soleen.com> <179439592040.425130.10808690337075841196.b4-review@b4> In-Reply-To: <179439592040.425130.10808690337075841196.b4-review@b4> On Wed Nov 11, 2026 at 6:18 AM EST, Mike Rapoport wrote: > Hi, > >> Currently, LUO freezes outgoing sessions only inside the >> reboot(LINUX_REBOOT_CMD_KEXEC) syscall path, serially under global write >> locks, and binds every outgoing session's lifetime strictly to an open >> session FD until reboot. >>=20 >> On hosts running many workloads (such as VMs or stateful daemons), >> workloads do not all pause simultaneously inside reboot(): they quiesce >> one by one ahead of the host kexec. Userspace needs an explicit >> per-session freeze point to snapshot final file state (.freeze()) as >> each workload pauses -- concurrently across sessions under per-session >> locks -- along with a way to commit a frozen session into KHO so it >> survives closing the session FD. >>=20 >> This series introduces LIVEUPDATE_SESSION_FREEZE on session FDs: >>=20 >> 1. Freeze (flags =3D=3D 0): >> Freezes all preserved files in the session under the per-session >> mutex while keeping session lifetime tied to the session FD. The >> session stays frozen as long as the FD remains open; closing the >> session FD before reboot (for example, to abort the session or on >> process exit/crash) runs .unfreeze() and .unpreserve() and reclaims >> all resources. At kexec time, already-frozen sessions skip the late >> auto-freeze step and are published into the outgoing KHO subtree. > > Let me bikeshed for a moment :) > I'm not fond of "published" terminology. We just moved serialization > from one place to another, why not keep the naming? sgtm, I serialization it is. --=20 Pasha