inotify on Samba4 and clustering

Andrew Bartlett abartlet at
Tue May 30 22:03:05 GMT 2006

On Tue, 2006-05-30 at 16:38 -0500, Abhijith Das wrote:
> Hi list,
> I was looking at the latest Samba4 code and found some use of the 
> inotify interface. I was told before that dnotify was being replaced by 
> inotify, so this is not a surprise.
> However, when I think of a clusterized implementation of inotify for 
> GFS, I see complications.
>  - An event-watch on one cluster node should be propagated to all nodes.
>  - When an event occurs on a different node, we need to somehow write to 
> the event-queue of the first node. This could mean some serious hacking.
>  - There are way too many events to use a distributed-lock-manager's 
> locking for internode communication. A separate userland event/messaging 
> framework would have to deal with these event notifications and pass 
> them around as necessary.
> Is the effort worth the reward? In what situations does samba use 
> inotify and what could be the performance impact without inotify support?

It is not a performance, but a correctness impact.  Windows clients use
change notify, (which we back onto inotify) frequently, and expect it to
work.  The simple case is that explorer won't update the display when a
remote user deletes a file, but it goes far beyond that.

> An alternate solution could be a local-inotify implementation. We could 
> add support in clustered-samba to pass these inotify messages to various 
> cluster nodes as appropriate?

I think this belongs in the filesystem, but somehow, every node that
might change these files must watch for them. 

Andrew Bartlett

Andrew Bartlett                      
Authentication Developer, Samba Team 
Student Network Administrator, Hawker College
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