Messages in this thread | | | From | "Huang, Ying" <> | Subject | Re: [PATCH 15/16] mm/migration: fix possible do_pages_stat_array racing with memory offline | Date | Mon, 07 Mar 2022 13:21:43 +0800 |
| |
Miaohe Lin <linmiaohe@huawei.com> writes:
> When follow_page peeks a page, the page could be reclaimed under heavy > memory pressure
I don't think that memory pressure and reclaiming will be an issue.
> and thus be offlined while it's still being used by the > do_pages_stat_array().
"offline" seems a possible problem.
Best Regards, Huang, Ying
> Use FOLL_GET to hold the page refcnt to fix this > potential issue. > > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> > --- > mm/migrate.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 7b1c0b988234..98a968e6f465 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1788,13 +1788,18 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, > goto set_status; > > /* FOLL_DUMP to ignore special (like zero) pages */ > - page = follow_page(vma, addr, FOLL_DUMP); > + page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); > > err = PTR_ERR(page); > if (IS_ERR(page)) > goto set_status; > > - err = page ? page_to_nid(page) : -ENOENT; > + if (page) { > + err = page_to_nid(page); > + put_page(page); > + } else { > + err = -ENOENT; > + } > set_status: > *status = err;
| |