Messages in this thread | | | From | "Aneesh Kumar K.V" <> | Subject | Re: [PATCHv4 19/24] thp, mm: use migration entries to freeze page counts on split | Date | Mon, 30 Mar 2015 21:15:47 +0530 |
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"Kirill A. Shutemov" <kirill@shutemov.name> writes:
> 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. >
This we can use
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
similar to what we do in freeze_page(). The difference between freeze/unfreeze confused me.
-aneesh
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