On 08/24/22 11:38, Andrew Morton wrote: > On Tue, 23 Aug 2022 21:58:40 +0800 Haiyue Wang <haiyue.wang@xxxxxxxxx> wrote: > > > Not all huge page APIs support FOLL_GET option, so move_pages() syscall > > will fail to get the page node information for some huge pages. > > > > Like x86 on linux 5.19 with 1GB huge page API follow_huge_pud(), it will > > return NULL page for FOLL_GET when calling move_pages() syscall with the > > NULL 'nodes' parameter, the 'status' parameter has '-2' error in array. > > > > Note: follow_huge_pud() now supports FOLL_GET in linux 6.0. > > Link: https://lore.kernel.org/all/20220714042420.1847125-3-naoya.horiguchi@xxxxxxxxx > > > > But these huge page APIs don't support FOLL_GET: > > 1. follow_huge_pud() in arch/s390/mm/hugetlbpage.c > > 2. follow_huge_addr() in arch/ia64/mm/hugetlbpage.c > > It will cause WARN_ON_ONCE for FOLL_GET. > > 3. follow_huge_pgd() in mm/hugetlb.c > > What happened to the proposal to fix these three sites so this patch is > not needed? > Note mpe's comments here: https://lore.kernel.org/linux-mm/87r113jgqn.fsf@xxxxxxxxxxxxxxxxxx/ It has been a while since powerpc supported hugetlb pages at the PGD level. And, this was the only architecture which had pages at this level. Unless I am missing something, this means there is no issue with follow_huge_pgd as there is no way this code could be invoked when commit 4cd614841c06 was made. -- Mike Kravetz
