Zi Yan <zi.yan@xxxxxxxxxxxxxx> writes:
> This cannot happen.
>
> Two address parameters are passed: addr and next.
> If “addr” is not aligned and “next” is aligned or the end of madvise range, which might not be aligned,
> either way next - addr < HPAGE_PMD_SIZE.
>
> This means the code in “if (next - addr != HPAGE_PMD_SIZE)”, which is above your second hunk,
> will split the THP between “addr” and “next” and get out as long as “addr“ is not aligned.
> Thus, the code in your second hunk should always get aligned “addr”.
>
> Let me know if I miss anything.
Yes, you are right! Thanks for pointing this out.
Sorry for bothering, please ignore this patch.
Best Regards,
Huang, Ying
> —
> Best Regards,
> Yan Zi
>
> On 14 Mar 2018, at 21:18, Huang, Ying wrote:
>
>> From: Huang Ying <ying.huang@xxxxxxxxx>
>>
>> The address argument passed in madvise_free_huge_pmd() may be not THP
>> aligned. But some THP operations like pmdp_invalidate(),
>> set_pmd_at(), and tlb_remove_pmd_tlb_entry() need the address to be
>> THP aligned. Fix this via using THP aligned address for these
>> functions in madvise_free_huge_pmd().
>>
>> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
>> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>> Cc: Minchan Kim <minchan@xxxxxxxxxx>
>> Cc: Shaohua Li <shli@xxxxxxxxxx>
>> Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
>> Cc: jglisse@xxxxxxxxxx
>> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>> ---
>> mm/huge_memory.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 0cc62405de9c..c5e1bfb08bd7 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -1617,6 +1617,7 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
>> struct page *page;
>> struct mm_struct *mm = tlb->mm;
>> bool ret = false;
>> + unsigned long haddr = addr & HPAGE_PMD_MASK;
>>
>> tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
>>
>> @@ -1663,12 +1664,12 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
>> unlock_page(page);
>>
>> if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
>> - pmdp_invalidate(vma, addr, pmd);
>> + pmdp_invalidate(vma, haddr, pmd);
>> orig_pmd = pmd_mkold(orig_pmd);
>> orig_pmd = pmd_mkclean(orig_pmd);
>>
>> - set_pmd_at(mm, addr, pmd, orig_pmd);
>> - tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
>> + set_pmd_at(mm, haddr, pmd, orig_pmd);
>> + tlb_remove_pmd_tlb_entry(tlb, pmd, haddr);
>> }
>>
>> mark_page_lazyfree(page);
>> --
>> 2.16.1
