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Subject: Re: Better interop for NFS/SMB file share mode/reservation
From:   =?utf-8?Q?Ralph_B=C3=B6hme?= <slow@samba.org>
In-Reply-To: <20190306210743.GE19279@jra3>
Date:   Wed, 6 Mar 2019 22:25:18 +0100
Cc:     Jeff Layton <jlayton@kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Volker.Lendecke@sernet.de, devel@lists.nfs-ganesha.org,
        Amir Goldstein <amir73il@gmail.com>,
        samba-technical <samba-technical@lists.samba.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
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To:     Jeremy Allison <jra@samba.org>
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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:
>>>=20
>>> Jeff, wasn't there some work (on Ceph maybe?) on a userspace =
delegation
>>> API?  Is that close to what's needed?
>>>=20
>>=20
>> Here's the C headers for that stuff:
>>=20
>>    =
https://github.com/ceph/ceph/blob/7ba6bece4187eda5d05a9b84211fe6ba8dd287bd=
/src/include/cephfs/libcephfs.h#L1734
>>=20
>> 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?).
>=20
> 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

>=20
> Here are the semantics:
>=20
> =
https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-smb2/d8df9=
43d-6ad7-4b30-9f58-96ae90fc6204
>=20
> 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