Be far more judicious in the use of curzone-using macros.

@@ -932,18 +932,25 @@
  */
 #define ZONE_SPECIALPID(x)       ((x) == 0 || (x) == 1)
 
 /*
  * The root vnode of the current zone.
+ *
+ * NOTE: It may be necessary (initialization time for file sharing where an
+ * NGZ loads a file-sharing kernel module that does zsd initialization) to NOT
+ * use this macro. One should ASSERT() that curzone == active ZSD (an
+ * ASSERTion that's not always true at ZSD initialization time) during regular
+ * use of this macro.
  */
 #define ZONE_ROOTVP()   (curzone->zone_rootvp)
 
 /*
  * Since a zone's root isn't necessarily an actual filesystem boundary
  * (i.e. VROOT may not be set on zone->zone_rootvp) we need to not assume it.
  * This macro helps in checking if a vnode is the current zone's rootvp.
  * NOTE:  Using the VN_ prefix, even though it's defined here in zone.h.
+ * NOTE2: See above warning about ZONE_ROOTVP().
  */
 #define VN_IS_CURZONEROOT(vp)   (VN_CMP(vp, ZONE_ROOTVP()))
 
 /*
  * Zone-safe version of thread_create() to be used when the caller wants to