On 04/11/2016 10:55 AM, Anshuman Khandual wrote: > On 04/07/2016 02:34 PM, Balbir Singh wrote: >> > >> > >> > On 07/04/16 15:37, Anshuman Khandual wrote: >>> >> Currently the config ARCH_WANT_GENERAL_HUGETLB enabled functions like >>> >> 'huge_pte_alloc' and 'huge_pte_offset' dont take into account HugeTLB >>> >> page implementation at the PGD level. This is also true for functions >>> >> like 'follow_page_mask' which is called from move_pages() system call. >>> >> This lack of PGD level huge page support prohibits some architectures >>> >> to use these generic HugeTLB functions. >>> >> >> > >> > From what I know of move_pages(), it will always call follow_page_mask() >> > with FOLL_GET (I could be wrong here) and the implementation below >> > returns NULL for follow_huge_pgd(). > You are right. This patch makes ARCH_WANT_GENERAL_HUGETLB functions aware > of PGD implementation so that we can do all transactions on 16GB pages > using these function instead of the present arch overrides. But that also > requires follow_page_mask() changes for every other access to the page > than the migrate_pages() usage. > > But yes, we dont support migrate_pages() on PGD based pages yet, hence > it just returns NULL in that case. May be the commit message needs to > reflect this. The next commit actually changes follow_huge_pud|pgd() functions to support FOLL_GET and PGD based huge page migration. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>