[PATCH] Make server-side copy (copy-chunk) async

[Ralph Böhme]

On Wed, Mar 22, 2017 at 01:22:23PM -0700, Jeremy Allison wrote:
> On Wed, Mar 22, 2017 at 07:14:05PM +0100, Ralph Böhme via samba-technical wrote:
> > Hi!
> > 
> > Attached is a patchset I've been working on that makes our server-side copy
> > asynchronous.
> > 
> > At the SMB layer the chunks are processed sequentially in order, but left to
> > right merged if copy ranges are adjecent. In the backend (vfs_default) I'm
> > essentially just using pread|pwrite_send|recv instead of the sync versions.
> > 
> > I'm also adding a small new feature to tevent: cancel forwarding. It allows the
> > implementation of a tevent request using subrequest to request forwarding of
> > cancels to be done automagically by the tevent library. This is useful for
> > forwarding cancels through a chain of subrequests.
> 
> OK. I have to ask the nasty question :-).
> 
> Do you *really* need to extend tevent to add this ?
> 
> You're only forwarding cancel to one event at a time.
> 
> Couldn't you just add a normal cancel function
> on the parent req, which calls tevent_req_cancel()
> on the subreq stored in the parent req private data ?

In the end I need the cancel to get all the way down to vfs_default, as that's
where the actual copying takes place, potentially in a loop (fruit:copyfile
case) copying some big file in *completely* in one subreq. *That*s the one I
want to be able to cancle, though admittedly the client doesn't support
cancelling a pending fruit:copyfile style copy.

Cf the last commit that adds a test for this.

Cheerio!
-slow