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SubjectRe: [patch 3/8] x86 PAT: Add follow_pfnmp_pte routine to help tracking pfnmap pages
On Wed, Nov 12, 2008 at 01:26:50PM -0800, Venkatesh Pallipadi wrote:
>
> Add a generic interface to follow pfn in a pfnmap vma range. This is used by
> one of the subsequent x86 PAT related patch to keep track of memory types
> for vma regions across vma copy and free.
>
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
>
> ---
> include/linux/mm.h | 3 +++
> mm/memory.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 46 insertions(+)
>
> Index: tip/include/linux/mm.h
> ===================================================================
> --- tip.orig/include/linux/mm.h 2008-11-06 15:41:43.000000000 -0800
> +++ tip/include/linux/mm.h 2008-11-10 09:44:45.000000000 -0800
> @@ -1223,6 +1223,9 @@ struct page *follow_page(struct vm_area_
> #define FOLL_GET 0x04 /* do get_page on page */
> #define FOLL_ANON 0x08 /* give ZERO_PAGE if no pgtable */
>
> +unsigned long follow_pfnmap_pte(struct vm_area_struct *vma,
> + unsigned long address, pte_t *ret_ptep);
> +
> typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
> void *data);
> extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
> Index: tip/mm/memory.c
> ===================================================================
> --- tip.orig/mm/memory.c 2008-11-06 15:41:43.000000000 -0800
> +++ tip/mm/memory.c 2008-11-10 09:44:45.000000000 -0800
> @@ -1111,6 +1111,49 @@ no_page_table:
> return page;
> }
>
> +unsigned long follow_pfnmap_pte(struct vm_area_struct *vma,
> + unsigned long address, pte_t *ret_ptep)
> +{

I think we'd typically return an int for functions like this. It
probably wouldn't hurt to return more descriptive errors either.
-EINVAL, perhaps, seems to fit best with what existing code there
is doing.

> + pgd_t *pgd;
> + pud_t *pud;
> + pmd_t *pmd;
> + pte_t *ptep, pte;
> + spinlock_t *ptl;
> + struct page *page;
> + struct mm_struct *mm = vma->vm_mm;
> +
> + if (!is_pfn_mapping(vma))
> + goto err;
> +
> + page = NULL;
> + pgd = pgd_offset(mm, address);
> + if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
> + goto err;
> +
> + pud = pud_offset(pgd, address);
> + if (pud_none(*pud) || unlikely(pud_bad(*pud)))
> + goto err;
> +
> + pmd = pmd_offset(pud, address);
> + if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
> + goto err;
> +
> + ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
> +
> + pte = *ptep;
> + if (!pte_present(pte))
> + goto err_unlock;
> +
> + *ret_ptep = pte;
> + pte_unmap_unlock(ptep, ptl);
> + return 0;
> +
> +err_unlock:
> + pte_unmap_unlock(ptep, ptl);
> +err:
> + return -1;
> +}
> +
> /* Can we do the FOLL_ANON optimization? */
> static inline int use_zero_page(struct vm_area_struct *vma)
> {
>
> --


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