Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1263184

Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new THP refcounting

Show all headers | View raw

On Thu, Nov 05, 2015 at 02:36:06PM +0200, Kirill A. Shutemov wrote:
> On Thu, Nov 05, 2015 at 03:07:26PM +0300, Vladimir Davydov wrote:
> > @@ -849,30 +836,23 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
> >  		if (pmd_page(*pmd) != page)
> >  			goto unlock_pmd;
> >  
> > -		if (vma->vm_flags & VM_LOCKED) {
> > -			pra->vm_flags |= VM_LOCKED;
> > -			ret = SWAP_FAIL; /* To break the loop */
> > -			goto unlock_pmd;
> > -		}
> > -
> > -		if (pmdp_clear_flush_young_notify(vma, address, pmd))
> > -			referenced++;
> > -		spin_unlock(ptl);
> > +		pte = (pte_t *)pmd;
> 
> pmd_t and pte_t are not always compatible. We shouldn't pretend they are.
> And we shouldn't use pte_unmap_unlock() to unlock pmd table.

Out of curiosity, is it OK that __page_check_address can call
pte_unmap_unlock on pte returned by huge_pte_offset, which isn't really
pte, but pmd or pud?

> 
> What about interface like this (I'm not sure about helper's name):
> 
> void page_check_address_transhuge(struct page *page, struct mm_struct *mm,
>                                    unsigned long address,
>                                    pmd_t **pmdp, pte_t **ptep,
> 				   spinlock_t **ptlp);
> 
> page_check_address_transhuge(page, mm, address, &pmd, &pte, &ptl);
> if (pmd) {
> 	/* handle pmd... */
> } else if (pte) {
> 	/* handle pte... */
> } else {
> 	return SWAP_AGAIN;
> }
> 
> /* common stuff */
> 
> if (pmd)
> 	spin_unlock(ptl);
> else 
> 	pte_unmap_unlock(pte, ptl);

spin_unlock(ptl);
if (pte)
	pte_unmap(pte);

would look neater IMO. Other than that, I think it's OK. At least, it
looks better and less error-prone than duplicating such a huge chunk of
code IMO.

Thanks,
Vladimir

> 
> /* ... */
> 
> The helper shouldn't set pmd if the page is tracked to pte.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH 0/4] Bugfixes for THP refcounting "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-11-03 16:30 +0100
  [PATCH 4/4] mm: prepare page_referenced() and page_idle to new THP refcounting "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-11-03 16:30 +0100
    Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting Vladimir Davydov <vdavydov@virtuozzo.com> - 2015-11-05 10:20 +0100
      Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-05 10:30 +0100
        Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting Vladimir Davydov <vdavydov@virtuozzo.com> - 2015-11-05 13:10 +0100
          Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-05 13:40 +0100
            Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-05 14:00 +0100
              Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting Vladimir Davydov <vdavydov@virtuozzo.com> - 2015-11-05 17:40 +0100
              [PATCH] mm: add page_check_address_transhuge helper Vladimir Davydov <vdavydov@virtuozzo.com> - 2015-11-06 15:40 +0100
                Re: [PATCH] mm: add page_check_address_transhuge helper "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-06 16:30 +0100
            Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting Vladimir Davydov <vdavydov@virtuozzo.com> - 2015-11-05 14:00 +0100
    Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting Vladimir Davydov <vdavydov@virtuozzo.com> - 2015-11-05 17:10 +0100
      Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-05 18:30 +0100
    Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting Andrew Morton <akpm@linux-foundation.org> - 2015-11-06 01:40 +0100
      Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-06 11:30 +0100
        Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting Andrew Morton <akpm@linux-foundation.org> - 2015-11-06 23:40 +0100
          Re: [PATCH 4/4] mm: prepare page_referenced() and page_idle to new  THP refcounting "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-09 00:50 +0100
  [PATCH 2/4] mm: duplicate rmap reference for hugetlb pages as compound "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-11-03 16:30 +0100
  [PATCH 3/4] thp: fix split vs. unmap race "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-11-03 16:30 +0100

csiph-web