"Kirill A. Shutemov" <kir...@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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