vwaitforio
vwaitforio (vp, 0, "spec_fsync", INFSLP);
vwaitforio(vp, 0, "vinvalbuf", INFSLP);
vwaitforio(vp, 0, "vflushbuf", INFSLP);
error = vwaitforio(vp, slpflag, "nfs_fsync", slptimeo);
int vwaitforio(struct vnode *, int, char *, uint64_t);
vwaitforio(vp, 0, "ffs_fsync", INFSLP);