lkml.org 
[lkml]   [2022]   [Aug]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v7 1/2] mm: migration: fix the FOLL_GET failure on following huge page
On Tue, 23 Aug 2022 21:58:40 +0800 Haiyue Wang <haiyue.wang@intel.com> 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@linux.dev
>
> 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?

> This is an temporary solution to mitigate the side effect of the race
> condition fix by calling follow_page() with FOLL_GET set for huge pages.
>
> After supporting follow huge page by FOLL_GET is done, this fix can be
> reverted safely.

\
 
 \ /
  Last update: 2022-08-24 20:39    [W:0.076 / U:0.252 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site