Missing protocol features that could help Linux

[Jeremy Allison]

On Fri, Apr 19, 2024 at 01:40:34PM +1200, Andrew Bartlett wrote:
>POSIX <-> POSIX locking over SMB is something I have a client trying to
>get working with SMB3.
>
>They have a use case where, as I understand it so far, the mapping of
>POSIX fcntl() read and write locks to SMB locks isn't 1-1, because they
>expect advisory locks, but SMB locks are mandatory as far as I read
>it.
>
>They use cifs.ko and Samba, so it isn't about working with Windows, it
>is about running Libreoffice on LInux against Samba.

That's not going to work the way LibreOffice on Linux expects,
until we fully expose POSIX locking semantics.

It's the range semantics that will probably break them.

POSIX locks can be split/merged/overlapped. Windows locks
must be distinct. Currently over SMB3 we only expose Windows
locks.