MFC r253497:
Use the right name for the vm_map_find(9) flag to specify shared mapping.
MFC r253709:
The pmap_qenter() and pmap_qremove() perform TLB invalidation on its
own, no need to call pmap_invalidate_range() one more time.
MFC r253417:
Clear the vnode knotes before destroying vpollinfo.

MFC r253737:
Split the destruction into the helper destroy_vpollinfo_free(), and
call it when raced, instead of destroy_vpollinfo().