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X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: cZvExqBnanhre2kfNutKwvbdSJW4WrNVi7OHi3Nz5uyudr80RrVs/saeJCF9Qou/55VaMy74x5e2Hix1SV42GrmAMaWrvduihI7jVcItGYc= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR10MB4614 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-14_07,2025-01-13_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 mlxscore=0 suspectscore=0 bulkscore=0 malwarescore=0 adultscore=0 spamscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2411120000 definitions=main-2501140163 X-Proofpoint-GUID: GYBLuWPbloqYnvHm4O2dz2h9QuOFGgBw X-Proofpoint-ORIG-GUID: GYBLuWPbloqYnvHm4O2dz2h9QuOFGgBw I've seen a few requests for implementing the NFS v4.2 WRITE_SAME [1] operation over the last few months [2][3] to accelerate writing patterns of data on the server, so it's been in the back of my mind for a future project. I'll need to write some code somewhere so NFS & NFSD can handle this request. I could keep any implementation internal to NFS / NFSD, but I'd like to find out if local filesystems would find this sort of feature useful and if I should put it in the VFS instead. I was thinking I could keep it simple, and model a function call based on write(3) / pwrite(3) to write some pattern N times starting at either the file's current offset or at a user-provide offset. Something like: write_pattern(int filedes, const void *pattern, size_t nbytes, size_t count); pwrite_pattern(int filedes, const void *pattern, size_t nbytes, size_t count, offset_t offset); I could then construct a WRITE_SAME call in the NFS client using this information. This seems "good enough" to me for what people have asked for, at least as a client-side interface. It wouldn't really help the server, which would still need to do several writes in a loop to be spec-compliant with writing the pattern to an offset inside the "application data block" [4] structure. But maybe I'm simplifying this too much, and others would find the additional application data block fields useful? Or should I keep it all inside NFS, and call it with an ioctl instead of putting it into the VFS? Thoughts? Anna [1]: https://datatracker.ietf.org/doc/html/rfc7862#section-15.12 [2]: https://lore.kernel.org/linux-nfs/CAAvCNcByQhbxh9aq_z7GfHx+_=S8zVcr9-04zzdRVLpLbhxxSg@mail.gmail.com/ [3]: https://lore.kernel.org/linux-nfs/CALWcw=Gg33HWRLCrj9QLXMPME=pnuZx_tE4+Pw8gwutQM4M=vw@mail.gmail.com/ [4]: https://datatracker.ietf.org/doc/html/rfc7862#section-8.1