Jason R Thorpe wrote:
> The reason that there is no callback mechanism is because NFS is stateless
> (well, it's supposed to be anyway :-) .. the server doesn't know which
> clients are currently active.

I wonder if NQNFS read lease could be (ab)used for this, but this
would depend on using NQNFS :/

> I don't think polling is right, either.  That will generate a lot of
> annoying network traffic.
> 
> Instead, I would say "only support kevents for local writes of the file",
> and document this behavior for the NFS case.

Yes, it could be done this way, but it's lame to have to handle NFS
specially in software.
 
The polling shouldn't generate too much network traffic, not more
than casual 'tail -f' causes for files on NFS. The polling would
basically do just GETATTR RPC couple times per second for every
file with registered kevents. Since there would be very few
watched files, this shouldn't particularily affect the network.

Jaromir
-- 
Jaromir Dolecek <jdolecek@NetBSD.org>            http://www.NetBSD.org/
-=- We should be mindful of the potential goal, but as the tantric    -=-
-=- Buddhist masters say, ``You may notice during meditation that you -=-
-=- sometimes levitate or glow.   Do not let this distract you.''     -=-