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Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Pasha Tatashin , Randy Dunlap , Samiullah Khawaja , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka Subject: Re: [PATCH v3 07/10] mm/shmem_luo: Retrieve tmpfs files onto a tmpfs mount chosen by userspace In-Reply-To: (David Matlack's message of "Wed, 4 Nov 2026 22:30:26 +0000") References: <20261103010216.3447716-1-dmatlack@google.com> <20261103010216.3447716-8-dmatlack@google.com> <2vxzecd0k1dg.fsf@kernel.org> Date: Fri, 06 Nov 2026 15:20:44 +0100 Message-ID: <2vxzfqxehwhv.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D407640009 X-Stat-Signature: euxy71kw36buxixnsnt4nf3w83oqzx5y X-Rspam-User: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1793974850-379422 X-HE-Meta: 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 yWBCPJf/ 5pASlwkHEw3BLwxlHU2NF9Qd7wU0m0S1lKKrX6jK9pAO/ugmGfXBOMVWAwm2OI0JB+eGrQ4/jPq/nLXonl/zqqyECukfS+n0BNUMqygNJXrejd74YL5VOmziXV2pkHoEZglMsgBZb6qiPwkKd7f3+c2Ia+GAYzQTYPTo1ucJF4reNGiKfP9jbUXfN6a/TbJYv7G9quEfkyskejtndv6qdHy+O576aVAKi7WzSWM3gtw918tc3iXJ/6CYKW4g7ccKL7XRK 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 04 2026, David Matlack wrote: > On 2026-11-04 05:27 PM, Pratyush Yadav wrote: > >> > + * If @flags contains unknown flags or O_PATH, if @mode contains unknown mode >> > + * bits, or if @dirfd is not on a tmpfs mount, the retrieve fails with -EINVAL. >> > + * If the file can't be created, the retrieve fails with the same errors as >> > + * open(). A retrieve that fails before the preserved contents are restored can >> > + * be retried. >> >> How is userspace supposed to tell if preserved contents were restored? > > Through the error code, like Pasha said on patch 3. I'll reword this in > v4 in terms of errors instead of kernel internals: errors from checking > the argument and creating the file, e.g. -EINVAL, -EBADF and the errors > that open() returns, can be retried after fixing the argument. Errors > while restoring the contents, e.g. -ENOMEM, or -ENOSPC when the contents > don't fit on the mount, are permanent, and retrieving the token again > returns the same error. I wonder if we should document per-file type error codes and what they mean. Perhaps some time in the future... > > Thanks for the review. I'll address the rest in v4. -- Regards, Pratyush Yadav