The patch titled
Subject: mm: migration: fix the FOLL_GET failure on following huge page
has been added to the -mm mm-unstable branch. Its filename is
mm-migration-fix-the-foll_get-failure-on-following-huge-page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migration-fix-the-foll_get-failure-on-following-huge-page.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Haiyue Wang <haiyue.wang@xxxxxxxxx>
Subject: mm: migration: fix the FOLL_GET failure on following huge page
Date: Fri, 12 Aug 2022 16:49:21 +0800
Not all huge page APIs support FOLL_GET option, so the __NR_move_pages
will fail to get the page node information for huge page.
This is an temporary solution to mitigate the racing fix.
After supporting follow huge page by FOLL_GET is done, this fix can be
reverted safely.
Link: https://lkml.kernel.org/r/20220812084921.409142-1-haiyue.wang@xxxxxxxxx
Fixes: 4cd614841c06 ("mm: migration: fix possible do_pages_stat_array racing with memory offline")
Signed-off-by: Haiyue Wang <haiyue.wang@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/mm/migrate.c~mm-migration-fix-the-foll_get-failure-on-following-huge-page
+++ a/mm/migrate.c
@@ -1852,6 +1852,7 @@ static void do_pages_stat_array(struct m
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;
@@ -1860,8 +1861,12 @@ static void do_pages_stat_array(struct m
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))
@@ -1869,7 +1874,8 @@ static void do_pages_stat_array(struct m
if (page && !is_zone_device_page(page)) {
err = page_to_nid(page);
- put_page(page);
+ if (foll_flags & FOLL_GET)
+ put_page(page);
} else {
err = -ENOENT;
}
_
Patches currently in -mm which might be from haiyue.wang@xxxxxxxxx are
mm-migration-fix-the-foll_get-failure-on-following-huge-page.patch
