blockif_size
off_t blockif_size(struct blockif_ctxt *bc);
sectors = blockif_size(p->bctx) / sectsz;
sectors = blockif_size(p->bctx) / 2048;
sectors = blockif_size(p->bctx) / blockif_sectsz(p->bctx);
sectors = blockif_size(p->bctx) / blockif_sectsz(p->bctx);
sc->nvstore.size = blockif_size(sc->nvstore.ctx);
size = blockif_size(bctxt);