Re: [PATCH 4/4] mm/page_alloc: remove set_page_private() in prep_compound_tail()

[Lance Yang <lance.yang@linux.dev>]

On Wed, Jul 01, 2026 at 10:58:21AM +0200, David Hildenbrand (Arm) wrote:
>On 6/29/26 04:56, Zi Yan wrote:
>> With the subpage->private == 0 check added in a prior commit, any allocated
>> compound page should not have nonzero subpage->private. Remove the

With Vlastimil's suggestion on patch #03, we still expect tail pages to
have 0 ->private when freed, but only check it when check_pages_enabled
is enabled :)

>> unnecessary subpage->private initialization code in compound page
>> preparation.
>> 
>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>> ---
>>  mm/internal.h | 1 -
>>  1 file changed, 1 deletion(-)
>> 
>> diff --git a/mm/internal.h b/mm/internal.h
>> index 181e79f1d6a2..c96421ce9350 100644
>> --- a/mm/internal.h
>> +++ b/mm/internal.h
>> @@ -895,7 +895,6 @@ static inline void prep_compound_tail(struct page *tail,
>>  {
>>  	tail->mapping = TAIL_MAPPING;
>>  	set_compound_head(tail, head, order);
>> -	set_page_private(tail, 0);
>
>Do we want another safety check, maybe another VM_WARN_ON_ONCE?

Right! I think such a check might still be useful. Same old footgun :P

Cheers, Lance