This patch should fix a problem that has been experienced on at-least one
busy NFS server, but it has not had lots of testing yet.  If -mm could provide
that .....

The rpc auth cache currently differentiates between a reference due to
being in a hash chain (signalled by CACHE_HASHED flag) and any other
reference (counted in refcnt).

This is an artificial difference due to an historical accident, and it
makes cache_put unsafe.

This patch removes the distinction so now existance in a hash chain is
counted just like any other reference.  Thus a race window in cache_put is
closed.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>