pnfs_register_layoutdriver
ret = pnfs_register_layoutdriver(&blocklayout_type);
ret = pnfs_register_layoutdriver(&scsilayout_type);
return pnfs_register_layoutdriver(&filelayout_type);
return pnfs_register_layoutdriver(&flexfilelayout_type);
EXPORT_SYMBOL_GPL(pnfs_register_layoutdriver);
extern int pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *);