K 10
svn:author
V 3
mjg
K 8
svn:date
V 27
2016-12-12T15:37:11.265252Z
K 7
svn:log
V 314
vfs: add vrefact, to be used when the vnode has to be already active

This allows blind increment of relevant counters which under contention
is cheaper than inc-not-zero loops at least on amd64.

Use it in some of the places which are guaranteed to see already active
vnodes.

Reviewed by:	kib (previous version)

END