On Wed, Jun 07, 2023 at 10:03:40PM -0400, Martin K. Petersen wrote: > > Dave, > > > Possibly unintentionally, I didn't call it REQ_OP_PROVISION but that's > > what I intended - the operation does not contain data at all. It's an > > operation like REQ_OP_DISCARD or REQ_OP_WRITE_ZEROS - it contains a > > range of sectors that need to be provisioned (or discarded), and > > nothing else. > > Yep. That's also how SCSI defines it. The act of provisioning a block > range is done through an UNMAP command using a special flag. All it does > is pin down those LBAs so future writes to them won't result in ENOSPC. *nod* That I knew, and it's one of the reasons I'd like the filesystem <-> block layer provisioning model to head in this direction. i.e. we don't have to do anything special to enable routing of provisioning requests to hardware and/or remote block storage devices (e.g. ceph-rbd, nbd, etc). Hence "external" devices can provide the same guarantees as a native software-only block device implementations like dm-thinp can provide and everything gets just that little bit better behaved... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
