How to turn on SMB3 POSIX extensions in Samba server?

[Jeremy Allison]

On Sat, Oct 05, 2019 at 11:02:21PM +0800, Chris Han via samba-technical wrote:
> Hi, I want to use the SMB3 POSIX extensions in the latest Samba (with
> SMB3.1.1, vers=3.1.1). By following the user manual, I have added the
> "posix" mount option when mounting, but it shows the following error
> messages.
> 
> Error messages:
> [xxxxx] CIFS VFS: Server does not support mounting with posix SMB3.11
> extensions.
> [xxxxx] CIFS VFS: cifs_mount failed w/return code = -95
> 
> Mount option:
> https://www.mankier.com/8/mount.cifs#posix%7Cunix%7Clinux
> https://wiki.samba.org/index.php/SMB3-Linux
> 
> Mount commands:
> mount –t cifs -o username=<user>,vers=3.1.1,posix //<address>/share
> /mnt/share
> mount –t cifs -o username=<user>,vers=3.1.1,posix,mfsymlinks
> //<address>/share /mnt/share
> 
> Software and kernel version:
> 1. Ubuntu 19.04, Kernel 5.0, Samba 4.10
> 2. Ubuntu 18.04.3, Kernel 5.0, Samba 4.7
> 
> Example of using the "vers=3.1.1,posix" mount option: (Page 46)
> https://www.snia.org/sites/default/files/SDC/2018/presentations/SMB/Steve_French_SMB311.pdf
> 
> How to turn on SMB3 POSIX extensions in Samba server?

There is no officially released version of Samba that
implements the SMB3 POSIX extensions yet. The code still
lives in an experimental branch that hasn't yet been
merged with mainline.

The plan is to finish the VFS refactoring, which will
bring the internals of Samba closer to the modern OpenGroup
handle-based VFS interface, then merge the extensions code
into mainline after that. The released code will be in
the next supported Samba version after the VFS refactoring
is done. Realistically, this will be sometime in 2020 unless
someone else wants to help me with the code :-).

Jeremy.