x86: PAT: add follow_pfnmp_pte routine to help tracking pfnmap pages - v3
Impact: New currently unused interface.
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>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/mm/memory.c b/mm/memory.c
index cef95c8..8ca6bbf 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1111,6 +1111,49 @@
return page;
}
+int follow_pfnmap_pte(struct vm_area_struct *vma, unsigned long address,
+ pte_t *ret_ptep)
+{
+ 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 -EINVAL;
+}
+
/* Can we do the FOLL_ANON optimization? */
static inline int use_zero_page(struct vm_area_struct *vma)
{