nagai/kernel
3
0
Fork 0
forked from mirrors/linux
Code Pull requests Activity

mm: migration: fix the FOLL_GET failure on following huge page

Browse source 
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

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.

Link: https://lkml.kernel.org/r/20220823135841.934465-2-haiyue.wang@intel.com
Link: https://lkml.kernel.org/r/20220812084921.409142-1-haiyue.wang@intel.com
Fixes: 4cd614841c ("mm: migration: fix possible do_pages_stat_array racing with memory offline")
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Haiyue Wang 2022-08-12 16:49:21 +08:00 committed by Andrew Morton
parent d3629af59f
commit 8315682148
1 changed files with 8 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
mm/migrate.c
View file

@ -1848,6 +1848,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
for (i = 0; i < nr_pages; i++) {
unsigned long addr = (unsigned long)(*pages);
unsigned int foll_flags = FOLL_DUMP;
struct vm_area_struct *vma;
struct page *page;
int err = -EFAULT;
@ -1856,8 +1857,12 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
if (!vma)
goto set_status;
/* Not all huge page follow APIs support 'FOLL_GET' */
if (!is_vm_hugetlb_page(vma))
foll_flags |= FOLL_GET;
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
page = follow_page(vma, addr, foll_flags);
err = PTR_ERR(page);
if (IS_ERR(page))
@ -1865,6 +1870,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
if (page && !is_zone_device_page(page)) {
err = page_to_nid(page);
if (foll_flags & FOLL_GET)
put_page(page);
} else {
err = -ENOENT;