zfs_mount
rv = zfs_mount(devformat(&dev->dd), NULL, (void **)&mount);
static int zfs_mount(const char *dev, const char *path, void **data);
.fo_mount = zfs_mount,
if (zfs_mount(spa, rootobj, &zfsmnt)) {
if (zfs_mount(spa, 0, &zfsmnt)) {