[Samba] Samba and BTRFS server-side copy

[Saint Germain]

On Thu, 27 Oct 2016 14:50:48 -0700, Jeremy Allison <jra at samba.org>
wrote :

> On Thu, Oct 27, 2016 at 11:27:29PM +0200, Saint Germain via samba
> wrote:
> > Hello,
> > 
> > I would like to test Samba server-side copy with BTRFS:
> > https://wiki.samba.org/index.php/Server-Side_Copy#Btrfs_Enhanced_Server-Side_Copy_Offload
> > 
> > However it is not clear which server/client configuration I should
> > use.
> > 
> > As far as I understand on the server-side, I should have at least
> > Samba 4.1 on a BTRFS filesystem (with vfs objects = btrfs in the
> > share).
> > 
> > But on the client side, what can I use ?
> > 
> > There is a warning on the page that:
> > "the client's FSCTL_SRV_COPYCHUNK server-side copy request must be
> > Btrfs filesystem aligned"
> > 
> > Digging a little more, I found some explanations here:
> > https://lists.samba.org/archive/samba-technical/2013-September/095135.html
> > 
> > > with Samba and Btrfs the request latency will be
> > > heavily effected by whether the FSCTL_SRV_COPYCHUNK wire request
> > > byte offsets and lengths align to the Btrfs sector-size (4K by
> > > default IIRC).
> > > If they do align, then each chunk in the request can be mapped to
> > > a BTRFS_IOC_CLONE_RANGE ioctl. Otherwise, we need to fall back to
> > > a server-side local read/write.
> > > 
> > > We should be able to provide underlying filesystem alignment
> > > requirements to SMB clients via the new
> > > FileFSSectorSizeInformation ioctl, but it's not currently
> > > supported by Samba.
> > 
> > So which client platform (Windows, Mac, Linux) and which client
> > software (smb, cifs, etc.) can I use to test this ?
> 
> Server-side copy can be requested using smbclient, using
> the "scopy" command.
> 
> It's a simple:
> 
> scopy source dest

Thanks but I just tested and it doesn't trigger BTRFS_IOC_CLONE_RANGE.
The server-side copy is working all right, but the file is not copied
through BTRFS reflink (cp --reflink=auto).
It is quite noticeable on large file, where it should be nearly
instantaneous.

My configuration:
 - client: Debian Stable + smbclient 4.4.6 (coming from Testing) +
   kernel 4.7 (amd64)
 - server: Debian Stable + samba 4.2.10 + kernel 4.7 (amd64)