On 08/23/2018 10:01 AM, Mike Kravetz wrote:
> On 08/23/2018 05:48 AM, Michal Hocko wrote:
>> On Tue 21-08-18 18:10:42, Mike Kravetz wrote:
>> [...]
>>
>> OK, after burning myself when trying to be clever here it seems like
>> your proposed solution is indeed simpler.
>>
>>> +bool huge_pmd_sharing_possible(struct vm_area_struct *vma,
>>> + unsigned long *start, unsigned long *end)
>>> +{
>>> + unsigned long check_addr = *start;
>>> + bool ret = false;
>>> +
>>> + if (!(vma->vm_flags & VM_MAYSHARE))
>>> + return ret;
>>> +
>>> + for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
>>> + unsigned long a_start = check_addr & PUD_MASK;
>>> + unsigned long a_end = a_start + PUD_SIZE;
>>
>> I guess this should be rather in HPAGE_SIZE * PTRS_PER_PTE units as
>> huge_pmd_unshare does.
>
> Sure, I can do that.
On second thought, this is more similar to vma_shareable() which uses
PUD_MASK and PUD_SIZE. In fact Kirill asked me to put in a common helper
for this and vma_shareable. So, I would prefer to leave it as PUD* unless
you feel strongly.
IMO, it would make more sense to change this in huge_pmd_unshare as PMD
sharing is pretty explicitly tied to PUD_SIZE. But, that is a future cleanup.
--
Mike Kravetz
