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

Wei Yang
2020-08-07T14:28:09Z

On Fri, Aug 07, 2020 at 08:49:51PM +0800, Baoquan He wrote:
>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);

Or we can remove this VM_BUG_ON()?

>> list_del(&nrg->link);
>>
>> --
>> 2.20.1 (Apple Git-117)
>>
>>

--
Wei Yang
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