[Samba] Documentation/Feature Clarification Request: Server Side Copy and VFS_FRUIT

[David Disseldorp]

Hi,

On Wed, 21 May 2025 09:46:34 +0200, Ralph Boehme via samba wrote:

> There are two styles of SSC:
> - the "normal" protocol style called copy-chunk, where the copy is 
> requested in IO ranges by the client and performed server-side
> - the Apple way enabled by fruit:copyfile where the client requests the 
> *whole* file to be copied in one request to be performed by the server
> 
> The problem with the latter is that for large file the copy takes some 
> time and meanwhile the client is blocked waiting for IO to complete. If 
> the copy takes longer then the SMB request timeout time (iirc default 
> 30s) the requests times out and the client will disconnect the connection.

APFS is a copy-on-write filesystem, according to Wikipedia. Assuming it
supports clones / reflinks, a 30s client timeout wouldn't appear
unreasonable.
Similarly for Linux, we could choose to only enable copyfile if the
underlying FS supports FICLONE (i.e. Btrfs, XFS v5 and perhaps ZFS).
Do Apple clients fallback to read/write on copyfile failure?

Cheers, David