Better interop for NFS/SMB file share mode/reservation

[Ralph Böhme]

Jeremy Allison wrote:
> On Wed, Mar 06, 2019 at 03:31:08PM -0500, Jeff Layton wrote:
>> On Wed, 2019-03-06 at 10:11 -0500, J. Bruce Fields wrote:
>>> 
>>> Jeff, wasn't there some work (on Ceph maybe?) on a userspace delegation
>>> API?  Is that close to what's needed?
>>> 
>> 
>> Here's the C headers for that stuff:
>> 
>>    https://github.com/ceph/ceph/blob/7ba6bece4187eda5d05a9b84211fe6ba8dd287bd/src/include/cephfs/libcephfs.h#L1734
>> 
>> It's simple enough and works for us in ganesha, and I think we can
>> probably adapt it to samba without too much difficulty. The callback
>> doesn't seem like it'll do for a kernel API though -- you'd almost
>> certainly need to do something different there (signals? inotify?).
> 
> SMB3 leases have R/RW and Handle-based leases.

Just to be precise: SMB2.1+ has R, RH, RW and RWH leases.

> Handle leases allow multiple opens of the same pathname
> that get different handles to share the lease, allowing
> a client redirector to delay opens or closes locally
> so long as it has a handle lease.

That'a a propertly of leases in general, not just H-leases. The client provides a lease key which is a GUID with each lease request

> 
> Here are the semantics:
> 
> https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-smb2/d8df943d-6ad7-4b30-9f58-96ae90fc6204
> 
> I'm not sure a simple file-descriptor based API is
> enough for us. Can he have a uuid or token based
> API instead where the server can chose what fd's
> to cover with a token ?

Yes, that would be ideal.

-slow