On Sat, Aug 9, 2025 at 1:12 PM David Noveck <davenoveck@xxxxxxxxx> wrote: > > > > On Friday, August 8, 2025, Rick Macklem <rick.macklem@xxxxxxxxx> wrote: >> >> On Fri, Aug 8, 2025 at 8:38 PM Trond Myklebust <trondmy@xxxxxxxxx> wrote: >> > >> > >> > >> > On Fri, Aug 8, 2025 at 9:47 PM Rick Macklem <rick.macklem@xxxxxxxxx> wrote: >> >> >> >> Hi, >> >> >> >> I'm looking at RFC7862 and I cannot find where it >> >> states if the clone_blksize attribute is per-file or >> >> per-file-system. >> >> >> >> If it is not in the RFC, which do others think it is? > > > Before you told us about ZFS, I would have assumed per-fs. > > Given the uncertainty in the spec, you may wind up dealing clients that assume it is per-fs. > > Although this is not a catastrophe, you might want to file an errata report explaining the negative consequences of assuming this is per-fs. It won't get into a spec for a long while but it does provide as much warning as you can right now . > > > >> >> >> (Or maybe, if you have implemented CLONE, >> >> which does your implementation assume?) >> >> >> >> In case you are wondering why I am asking, >> >> it turns out that files in a ZFS volume can have >> >> different block sizes. (It can be changed after the >> >> file system is created.) > > > The guy who allowed that probably thinks it's a helpful feature. Sigh! It's not just a feature change after creation, it turns out to be based on file size as well. A small file gets 512 and a larger one gets a full record (128K on my test system). And, yes, block cloning requires alignment with 512bytes or 128Kbytes depending on the file. I can return 128K for clone_blksize and that will (sub-optimally) handle the 512byte case, but I think it is also possible to increase the record size from 128K-> after the file system has files in it. I'll take a look at the Linux client to try and see if/how it uses clone_blksize. I need to decide if I should always return 128K (or whatever the full recordsize is) or 512 for the small files. Thanks for the comments, rick > >> >> > > >> >> >> Thanks, rick >> >> >> > >> > Yes, but since ZFS only supports filesystem level snapshots, and not actual file cloning, does that matter to anything? >> ZFS now has a feature it calls block cloning, which does clone file ranges. >> (It was only added recently. I do not know if the Linux port uses it yet?) >> >> rick >> >> > >> > Cheers >> > Trond >> >> _______________________________________________ >> nfsv4 mailing list -- nfsv4@xxxxxxxx >> To unsubscribe send an email to nfsv4-leave@xxxxxxxx
