subsystem. Add a test for VI_DOOMED just after ncl_upgrade_vnlock() in
ncl_bioread_check_cons(). This is required since it is possible
for the vnode to be vgonel()'d while in ncl_upgrade_vnlock() when
a forced dismount is in progress. Also, move the check for VI_DOOMED
in ncl_vinvalbuf() down to after ncl_upgrade_vnlock() and replace the
out of date comment for it.
Approved by: kib (mentor)