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mm/migration: fix possible do_pages_stat_array racing with memory offline

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When follow_page peeks a page, the page could be migrated and then be
offlined while it's still being used by the do_pages_stat_array().  Use
FOLL_GET to hold the page refcnt to fix this potential race.

Link: https://lkml.kernel.org/r/20220318111709.60311-12-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Miaohe Lin 2022-04-28 23:16:08 -07:00 committed by akpm
parent 3f26c88bd6
commit 4cd614841c
1 changed files with 7 additions and 2 deletions
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9
mm/migrate.c
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@ -1796,13 +1796,18 @@ 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;