On Tue, Nov 24, 2015 at 11:09:30AM +0200, Kirill A. Shutemov wrote:
> On Tue, Nov 24, 2015 at 01:29:41PM +0900, Sergey Senozhatsky wrote:
...
> > mm/built-in.o: In function `page_referenced_one':
> > rmap.c:(.text+0x32070): undefined reference to `pmdp_clear_flush_young'
> 
> Something like this?
...
> @@ -929,9 +929,12 @@ static int page_referenced_one(struct page *page, struct 
> vm_area_struct *vma,
>                               referenced++;
>               }
>               pte_unmap(pte);
> -     } else {
> +     } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
>               if (pmdp_clear_flush_young_notify(vma, address, pmd))
>                       referenced++;
> +     } else {
> +             /* unexpected pmd-mapped page? */
> +             WARN_ON_ONCE(1);
>       }
>       spin_unlock(ptl);

I think we'd better compile out page_check_address_transhuge altogether if
CONFIG_TRANSPARENT_HUGEPAGE is disabled and use page_check_address instead.
This would also reduce the kernel size a bit.
---
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b9eedc63e9e6..77d1ba57d495 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -219,9 +219,20 @@ static inline pte_t *page_check_address(struct page *page, 
struct mm_struct *mm,
  * Used by idle page tracking to check if a page was referenced via page
  * tables.
  */
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 bool page_check_address_transhuge(struct page *page, struct mm_struct *mm,
                                  unsigned long address, pmd_t **pmdp,
                                  pte_t **ptep, spinlock_t **ptlp);
+#else
+static inline bool page_check_address_transhuge(struct page *page,
+                               struct mm_struct *mm, unsigned long address,
+                               pmd_t **pmdp, pte_t **ptep, spinlock_t **ptlp)
+{
+       *ptep = page_check_address(page, mm, address, ptlp, 0);
+       *pmdp = NULL;
+       return !!*ptep;
+}
+#endif
 
 /*
  * Used by swapoff to help locate where page is expected in vma.
diff --git a/mm/rmap.c b/mm/rmap.c
index 27916086ac50..6f371261dd12 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -798,6 +798,7 @@ int page_mapped_in_vma(struct page *page, struct 
vm_area_struct *vma)
        return 1;
 }
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 /*
  * Check that @page is mapped at @address into @mm. In contrast to
  * page_check_address(), this function can handle transparent huge pages.
@@ -885,6 +886,7 @@ found:
        *ptlp = ptl;
        return true;
 }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 struct page_referenced_arg {
        int mapcount;
--
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