Re: [PATCH -mm v2] mm: add page_check_address_transhuge helper

From: Vladimir Davydov
Date: Tue Nov 24 2015 - 04:36:42 EST


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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