| Date | Mon, 30 Mar 2015 18:26:52 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCHv4 19/24] thp, mm: use migration entries to freeze page counts on split |
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On Mon, Mar 30, 2015 at 08:38:08PM +0530, Aneesh Kumar K.V wrote: > .... > .... > +static void freeze_page(struct anon_vma *anon_vma, struct page *page) > > +{ > > + struct anon_vma_chain *avc; > > + struct vm_area_struct *vma; > > + pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); > > So this get called only with head page, We also do > BUG_ON(PageTail(page)) in the caller. But > > > > + unsigned long addr, haddr; > > + unsigned long mmun_start, mmun_end; > > + pgd_t *pgd; > > + pud_t *pud; > > + pmd_t *pmd; > > + pte_t *start_pte, *pte; > > + spinlock_t *ptl; > ...... > > > > + > > +static void unfreeze_page(struct anon_vma *anon_vma, struct page *page) > > +{ > > + struct anon_vma_chain *avc; > > + pgoff_t pgoff = page_to_pgoff(page); > > Why ? Can this get called for tail pages ?
It cannot. pgoff is offset of head page (and therefore whole compound page) within rmapping.
-- Kirill A. Shutemov
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