vfs_start
if (vfsops->vfs_start == NULL) {
vfsops->vfs_start = vfs_stdstart;
error = (mp->mnt_op->vfs_start)(mp, flags);
int vfs_start(struct mount *mp, int flags);
vfs_start_t *vfs_start;
vfs_start(MP, FLAGS)
.vfs_start = mfs_start,