On Fri, Oct 12, 2012 at 11:23:37AM +0800, Ni zhan Chen wrote:

On 10/02/2012 11:19 PM, Kirill A. Shutemov wrote:

quoted

From: "Kirill A. Shutemov" <redacted>

We can't split huge zero page itself, but we can split the pmd which
points to it.

On splitting the pmd we create a table with all ptes set to normal zero
page.

Signed-off-by: Kirill A. Shutemov <redacted>
Reviewed-by: Andrea Arcangeli <redacted>
---
 mm/huge_memory.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 95032d3..3f1c59c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c

@@ -1600,6 +1600,7 @@ int split_huge_page(struct page *page)
 	struct anon_vma *anon_vma;
 	int ret = 1;
+	BUG_ON(is_huge_zero_pfn(page_to_pfn(page)));
 	BUG_ON(!PageAnon(page));
 	anon_vma = page_lock_anon_vma(page);
 	if (!anon_vma)

@@ -2503,6 +2504,32 @@ static int khugepaged(void *none)
 	return 0;
 }
+static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
+		unsigned long haddr, pmd_t *pmd)
+{
+	pgtable_t pgtable;
+	pmd_t _pmd;
+	int i;
+
+	pmdp_clear_flush_notify(vma, haddr, pmd);

why I can't find function pmdp_clear_flush_notify in kernel source
code? Do you mean pmdp_clear_flush_young_notify or something like
that?

It was changed recently. See commit
2ec74c3 mm: move all mmu notifier invocations to be done outside the PT lock

-- 
 Kirill A. Shutemov

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