Re: [PATCH v2 1/5] mm/hugetlb: fix races when looking up a CONT-PTE size hugetlb page

[David Hildenbrand]

>> +		/*
>> +		 * try_grab_page() should always succeed here, because we hold
>> +		 * the ptl lock and have verified pte_present().
>> +		 */
>> +		if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
>> +			page = NULL;
>> +			goto out;
>> +		}
>> +	} else {
> 
> Should add FOLL_MIGRATION validation before waiting a migration entry.

We really only need FOLL_MIGRATION for KSM. As hugetlb pages cannot be
KSM pages, we don't need this.

Actually, I do have patches in the works that rip out FOLL_MIGRATION
completely by adjusting KSM code.

So let's try to not add dead code (although it would make sense for
feature completeness as is -- but then, FOLL_MIGRATION really needs to go).

-- 
Thanks,

David / dhildenb