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Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , Randy Dunlap , Samiullah Khawaja , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka Subject: Re: [PATCH v3 03/10] liveupdate: Allow file handlers to mark retrieve failures as retryable In-Reply-To: <20261103010216.3447716-4-dmatlack@google.com> (David Matlack's message of "Tue, 3 Nov 2026 01:02:09 +0000") References: <20261103010216.3447716-1-dmatlack@google.com> <20261103010216.3447716-4-dmatlack@google.com> Date: Wed, 04 Nov 2026 15:12:26 +0100 Message-ID: <2vxzv76ck7n9.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain X-Stat-Signature: cxrsi4oedfweu46grrt45ogatmafb4e1 X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-12.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: DA01612000D X-HE-Tag: 1793801553-631071 X-HE-Meta: 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 vIusatgK WFNnRYH2/JNUZW5TTV22noFoueajR3Khxkb6vW56dJAUtdvlMBXhUFM3cutA1QHvhfNKiX4fuZqrtIFn2iSFcS1InKuyfAj0D+tFZ4YxWLWL+XB5pmrlf6hQg4lYX6F46vgUgzH7aZQKuPdMJL0Ea+d8KS3o8c+tMp0xNvsyOQ3tO4fsZIX1c1+XVwgO59KQo87hNphOFMhGru/WOkbyZBeePAc4hLqNuaSWK3ushLA39g0iWef0+HwDL3xi8J+A35ozv0jbjF4dJIOn3+EHjahDUomwdmwWKQouVUb7E87o2Unc= 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 Tue, Nov 03 2026, David Matlack wrote: > From: Pasha Tatashin > > When luo_retrieve_file() invokes a handler's .retrieve() callback and it > returns an error, LUO currently records the error in > luo_file->retrieve_status and blocks any subsequent retrieve attempts. > This is necessary when the handler has already partially consumed or > freed the preserved KHO state. > > However, with user arguments passed to .retrieve(), a handler may fail > early while validating caller-supplied parameters (such as a missing > argument, an invalid or read-only target file descriptor, or a non-empty > target file) before touching any preserved KHO state. In such cases, > userspace should be able to fix the argument and retry > LIVEUPDATE_SESSION_RETRIEVE_FD, and if the file is never retrieved, > .finish() must still run to release the preserved KHO state. > > Add a retryable output flag to struct liveupdate_file_op_args. When a > handler sets args->retryable = true on error, luo_retrieve_file() leaves > luo_file->retrieve_status at 0 so the retrieve operation can be retried > and .finish() will still clean up the unconsumed preserved state if the > session is finished without retrieving the file. Should we give some sort of signal to userspace whether the error is retriable or not? How would it know it can or should try again? > > Signed-off-by: Pasha Tatashin > Signed-off-by: David Matlack [...] -- Regards, Pratyush Yadav