linux-kernel - [PATCH, RFC 2/9] thp: zap_huge

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Date:	Thu,  9 Aug 2012 12:08:13 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org
Cc:	Andi Kleen <ak@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH, RFC 2/9] thp: zap_huge_pmd(): zap huge zero pmd

From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>

We don't have a real page to zap in huge zero page case. Let's just
clear pmd and remove it from tlb.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/huge_memory.c |   27 +++++++++++++++++----------
 1 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 88e0a7a..9dcb9e6 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1071,16 +1071,23 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		struct page *page;
 		pgtable_t pgtable;
 		pgtable = get_pmd_huge_pte(tlb->mm);
-		page = pmd_page(*pmd);
-		pmd_clear(pmd);
-		tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
-		page_remove_rmap(page);
-		VM_BUG_ON(page_mapcount(page) < 0);
-		add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
-		VM_BUG_ON(!PageHead(page));
-		tlb->mm->nr_ptes--;
-		spin_unlock(&tlb->mm->page_table_lock);
-		tlb_remove_page(tlb, page);
+		if (is_huge_zero_pmd(*pmd)) {
+			pmd_clear(pmd);
+			tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+			tlb->mm->nr_ptes--;
+			spin_unlock(&tlb->mm->page_table_lock);
+		} else {
+			page = pmd_page(*pmd);
+			pmd_clear(pmd);
+			tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+			page_remove_rmap(page);
+			VM_BUG_ON(page_mapcount(page) < 0);
+			add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
+			VM_BUG_ON(!PageHead(page));
+			tlb->mm->nr_ptes--;
+			spin_unlock(&tlb->mm->page_table_lock);
+			tlb_remove_page(tlb, page);
+		}
 		pte_free(tlb->mm, pgtable);
 		ret = 1;
 	}
-- 
1.7.7.6

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