Re: PUFFS lookup/reclaim race

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

On Fri, Jul 13, 2012 at 07:58:54AM +0000, David Holland wrote:
> Yeah: don't return copies of things that are basically pointers (in
> this case, the cookie) without doing proper usage tracking on them. It
> isn't valid to reclaim something that someone else is using; 

The problem is that the kernel reclaims a vnode that is not yet
been used by lookup. 

When kernel sends a lookup reuest to userland, it causes a node
to be referenced in userland, but it does not know what vnode
is associated before it gets the lookup reply. If the vnode
already existed, it can be reclaimed before the lookup reply,
there is no way to hold a reference on it, as we do not yet
know what vnode we have to work with.

-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost