Thoughts on how to communicate to VFS functions that a CREATE is occurring

[Volker Lendecke]

On Mon, Apr 04, 2016 at 07:26:46AM -0700, Richard Sharpe wrote:
> On Sun, Apr 3, 2016 at 11:15 PM, Volker Lendecke
> <Volker.Lendecke at sernet.de> wrote:
> > On Sun, Apr 03, 2016 at 10:26:40AM -0700, Richard Sharpe wrote:
> >> Well, we have implemented it, but it involved changes in Samba that I
> >> would like to get rid of.
> >>
> >> The feature is sharding of directories across multiple servers in a
> >> cluster and using DFS referrals to get clients connected to the
> >> correct server in the cluster.
> >>
> >> When a client asks you for a DFS referral for the directory that is on
> >> the node they are connected to (which they do, from time to time) we
> >> need to return the correct information.
> >>
> >> To do all of the above successfully, we have found that we need to
> >> know, in the VFS layer (and particularly, in STAT, which is pretty
> >> much the earliest VFS function called) whether we were called for a
> >> CREATE or for something else.
> >
> > What is the sequence of events? You get a SMB_CREATE, and you return a
> > PATH_NOT_COVERED. Then you get an ioctl that asks for the target path.
> > Is that right?
> 
> Yeah, that's the sequence.
> 
> > Intercepting create_fn is not sufficient, because it is called from other
> > highlevel SMB requests too?
> 
> That too. However,. more importantly, things like stat_fn is called
> before create_fn is called.

And you can't succeed with the stat_fn and later in the create_file_fn
return either success or NOT_COVERED?

Maybe it's time that we take a look at your patches. Do you also have
testcases covering your requirements?

Volker

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