8c392da154
can sleep on the vnode lock, while vget is sleeping on the VI_INACTNOW flag (or the vget caller is looping on vget returning failure because of the VI_INACTNOW flag). With layered FSes, the upper and lower vnodes share the same lock, so the vget() caller above can be already holding the vnode lock. Fix by dropping VI_INACTNOW before sleeping on the vnode lock in vrelel(), and check the ref count again once we have the lock. If the vnode has more than one reference, donc VOP_INACTIVE it. Fix PR kern/42318 and PR kern/42377 patch tested by Hisashi T Fujinaka, Joachim König, Stephen Borrill and Matthias Scheler.