Honestly, I don't know the usecase for re-exporting another server's NFS export in the first place. Is this someone trying to share NFS through a firewall? I've seen people share remote NFS exports via Samba in an attempt to avoid paying their NAS vendor for SMB support. (I think it's "standard equipment" now, but 10+ years ago? Not always...) But re-exporting another server's NFS exports? Haven't seen anyone do that in a while. Using "only local locks for reexport" would mean that -- in cases where different clients access the underlying export directly and others access the re-export -- you would have 2 different sources of "truth" with respect to locks... I have supported multiple tools that used file or byte-range record locks in my career... And this could easily royally hork any shared databases... Regards, Brian Cowan Regards, Brian Cowan ClearCase/VersionVault SWAT Mob: +1 (978) 907-2334 hcltechsw.com On Tue, Oct 29, 2024 at 10:11 AM Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote: > > > > > On Oct 29, 2024, at 9:57 AM, Martin Wege <martin.l.wege@xxxxxxxxx> wrote: > > > > On Wed, Oct 23, 2024 at 5:58 PM Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > >> > >> We do not and cannot support file locking with NFS reexport over > >> NFSv4.x for the same reason we don't do it for NFSv3: NFS reexport > >> server reboot cannot allow clients to recover locks because the source > >> NFS server has not rebooted, and so it is not in grace. Since the > >> source NFS server is not in grace, it cannot offer any guarantees that > >> the file won't have been changed between the locks getting lost and > >> any attempt to recover/reclaim them. The same applies to delegations > >> and any associated locks, so disallow them too. > >> > >> Add EXPORT_OP_NOLOCKSUPPORT and exportfs_lock_op_is_unsupported(), set > >> EXPORT_OP_NOLOCKSUPPORT in nfs_export_ops and check for it in > >> nfsd4_lock(), nfsd4_locku() and nfs4_set_delegation(). Clients are > >> not allowed to get file locks or delegations from a reexport server, > >> any attempts will fail with operation not supported. > > > > Are you aware that this virtually castrates NFSv4 reexport to a point > > that it is no longer usable in real life? > > "virtually castrates" is pretty nebulous. Please provide a > detailed (and less hostile) account of an existing application > that works today that no longer works when this patch is > applied. Only then can we count this as a regression report. > > > > If you really want this, > > then the only way forward is to disable and remove NFS reexport > > support completely. > > "No locking" is already the way NFSv3 re-export works. > > At the moment I cannot remember why we chose not to go with > the "only local locking for re-export" design instead. > > > -- > Chuck Lever > >
