rwfsblk
error = rwfsblk(snapvp, B_READ, bp->b_data, lbn);
static int rwfsblk(struct vnode *, int, void *, daddr_t);
rwfsblk(bp->b_vp, B_READ, bp->b_data, ffs_fragstoblks(fs, blkno)))) {
error = rwfsblk(vp, B_READ, saved_data, lbn);
error = rwfsblk(vp, B_READ, saved_data, lbn);
error = rwfsblk(vp, B_WRITE, bp->b_data,
error = rwfsblk(vp, B_READ, bp->b_data, loc);