Re: [PATCH 02/10] mm/hugetlb: make sure to get NULL when list is empty

Baoquan He
2020-08-07T12:50:04Z

On 08/07/20 at 05:12pm, Wei Yang wrote:
> list_first_entry() may not return NULL even when the list is empty.
>
> Let's make sure the behavior by using list_first_entry_or_null(),
> otherwise it would corrupt the list.
>
> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
> ---
> mm/hugetlb.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 62ec74f6d03f..0a2f3851b828 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -237,7 +237,8 @@ get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
> VM_BUG_ON(resv->region_cache_count <= 0);

We have had above line, is it possible to be NULL from list_first_entry?

>
> resv->region_cache_count--;
> - nrg = list_first_entry(&resv->region_cache, struct file_region, link);
> + nrg = list_first_entry_or_null(&resv->region_cache,
> + struct file_region, link);
> VM_BUG_ON(!nrg);
> list_del(&nrg->link);
>
> --
> 2.20.1 (Apple Git-117)
>
>