On 08/22/2018 02:05 PM, Kirill A. Shutemov wrote:
> On Tue, Aug 21, 2018 at 06:10:42PM -0700, Mike Kravetz wrote:
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 3103099f64fd..f085019a4724 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -4555,6 +4555,9 @@ static bool vma_shareable(struct vm_area_struct *vma,
>> unsigned long addr)
>>
>> /*
>> * check on proper vm_flags and page table alignment
>> + *
>> + * Note that this is the same check used in huge_pmd_sharing_possible.
>> + * If you change one, consider changing both.
>
> Should we have helper to isolate the check in one place?
>
Yes, I will create one. Most likely just a #define.
>> */
>> if (vma->vm_flags & VM_MAYSHARE &&
>> vma->vm_start <= base && end <= vma->vm_end)
>> @@ -4562,6 +4565,43 @@ static bool vma_shareable(struct vm_area_struct *vma,
>> unsigned long addr)
>> return false;
>> }
>>
>> +/*
>> + * Determine if start,end range within vma could be mapped by shared pmd.
>> + * If yes, adjust start and end to cover range associated with possible
>> + * shared pmd mappings.
>> + */
>> +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;
>
> Do we ever use return value? I don't see it.
>
> And in this case function name is not really work...
You are correct. None of the code uses the return value. I initially
thought some caller would use it. But every caller wants/needs to
adjust the range if sharing is possible. This is a really long name
but how about:
void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)
I'm open to other names and will update patch with suggestions.
--
Mike Kravetz
>
>> + 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;
>> +
>> + /*
>> + * If sharing is possible, adjust start/end if necessary.
>> + *
>> + * Note that this is the same check used in vma_shareable. If
>> + * you change one, consider changing both.
>> + */
>> + if (vma->vm_start <= a_start && a_end <= vma->vm_end) {
>> + if (a_start < *start)
>> + *start = a_start;
>> + if (a_end > *end)
>> + *end = a_end;
>> +
>> + ret = true;
>> + }
>> + }
>> +
>> + return ret;
>> +}
>> +
