On Tue, Jul 13, 2010 at 03:04:00PM +0900, Minchan Kim wrote: > > __get_user() works with TLB and page table, the vaddr is really mapped or not. > > If you got SEGV, __get_user() returns -EFAULT. It works per page granule. Not in kernel space. It works on 1MB sections there. Testing whether a page is mapped by __get_user is a hugely expensive way to test whether a PFN is valid. It'd be cheaper to use our flatmem implementation of pfn_valid() instead. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>