On Mon, Aug 10, 2020 at 01:28:46PM -0700, Mike Kravetz wrote: >On 8/7/20 7:28 AM, Wei Yang wrote: >> 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@xxxxxxxxxxxxxxxxx> >>>> --- >>>> 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()? >> > >I would prefer that we just remove the 'VM_BUG_ON(!nrg)'. Code elsewhere >is responsible for making sure there is ALWAYS an entry in the cache. That >is why the 'VM_BUG_ON(resv->region_cache_count <= 0)' is at the beginning >of the routine. Sure, will change to this. > >-- >Mike Kravetz -- Wei Yang Help you, Help me
