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b=PiVE8uzMlUpbGMOt63k6vT8hw2abfpbdQAia0dP8s95gP0HGX5fqQBVw6T71VApzj KxmYgAGG71dqGOdUg4HjnG6IuQfg5PpRaH9zD70xx5QpJ7SyM66AJNLOx41zAmQA76 Se7qyl+Bj42AlkZ9gFU1Kz+G0qbs1PPVvgf6TZpliCSjdo57yFzup0baGiLn44pKgD ovt78WFggNj7PnxWuPJy7GVjcsYBZ9hWBPefxqqiLlACZYHUOKyU51ZYZ1hV8/c5am LqW7CgaFMV4iZ3wVEipl+0eGPKrwlgcDDl07AGZJpMGkGhJL2ogQFrtaNtLOsITVkS VYdo9nZgRP7GA== Date: Tue, 18 Nov 2025 13:21:34 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, 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, 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, ptyadav@amazon.de, 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 Subject: Re: [PATCH v6 02/20] liveupdate: luo_core: integrate with KHO Message-ID: References: <20251115233409.768044-1-pasha.tatashin@soleen.com> <20251115233409.768044-3-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: jou86b3o417zqxrc5qqzubd6dtgbzcw4 X-Rspam-User: X-Rspamd-Queue-Id: 0E93280009 X-Rspamd-Server: rspam10 X-HE-Tag: 1763464921-747556 X-HE-Meta: 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 xwVKZmbL OGV5s+nyuxnEHKZWEDNnIq+YVjSePyYNfDITb17CV5ocnsyuOOke4yK7rsUc7le2MRMIhe9XftMShu2q39qN1qY13be2Msu+8Ul99LKKJUm3BmgC1KQgqF4gG/k9ZPDkSRF6sJDIBvgtQUMHgQYLpu8GA8oB8AdrmLVwUJsJ7cDSNIyObcl/KrzsUjU1NogMERmQYW2RudCf8mfMMU3jvUEYJI/v15DUBbvTTLnQqebw7bBy9fz3wXvj1FkjGFx55ST69LJXBP+ZCbvD7B+Xd+HWrpKeCgVM1+CmSA80wdu3wNMEq+M4SFIvq6udbKuIET8IdjwFIhBixXGLjNtjDixhC6SF2v1D2SUJnM6tz8acPrAQ6AYbOwhDXfo/Zcq4jhN7Ak9ZQ5nYxrC8= 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 Mon, Nov 17, 2025 at 11:22:54PM -0500, Pasha Tatashin wrote: > > You can avoid that complexity if you register the device with a different > > fops, but that's technicality. > > > > Your point about treating the incoming FDT as an underlying resource that > > failed to initialize makes sense, but nevertheless userspace needs a > > reliable way to detect it and parsing dmesg is not something we should rely > > on. > > I see two solutions: > > 1. LUO fails to retrieve the preserved data, the user gets informed by > not finding /dev/liveupdate, and studying the dmesg for what has > happened (in reality in fleets version mismatches should not be > happening, those should be detected in quals). > 2. Create a zombie device to return some errno on open, and still > study dmesg to understand what really happened. User should not study dmesg. We need another solution. What's wrong with e.g. ioctl()? > I think that 1 is better > > Pasha -- Sincerely yours, Mike.