Re: serious performance regression in .41

[David Laight <david%l8s.co.uk@localhost>]

On Thu, May 22, 2014 at 07:42:51PM +0200, J. Hannken-Illjes wrote:
> 
> While I'm interested in the results, this change is wrong.  As long as
> we have forced unmount and revoke it is not safe to access an inode
> without locking the corresponding vnode.  Holding a reference to the
> vnode just guarantees the vnode will not disappear, it does not
> prevent the inode from disappearing.

Forced unmount and revoke can use other synchronisation techniques
that are expensive for the unusual operation but cheap in the normal path.

Something like rcu would do.
Might even be more generally useful for some of these structures.

        David

-- 
David Laight: david%l8s.co.uk@localhost