for RPC operations when it can. Since VFS_FHTOVP() currently
always gets an exclusively locked vnode and is usually called
at the beginning of each RPC, the RPCs for a given vnode will
still be serialized. As such, passing a lock type argument to
VFS_FHTOVP() would be preferable to doing the vn_lock() with
LK_DOWNGRADE after the VFS_FHTOVP() call.
Reviewed by: kib
MFC after: 2 weeks
17891d0082