[RFC PATCH -V2 15/21] mm/THP: support for zerout withdraw.

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/s390/include/asm/pgtable.h     |    6 ++++++
 arch/sparc/include/asm/pgtable_64.h |    6 ++++++
 include/asm-generic/pgtable.h       |    9 +++++++++
 mm/huge_memory.c                    |    7 ++++++-
 4 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 883296e..2e8b7fe 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1238,6 +1238,12 @@ extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 #define __HAVE_ARCH_PGTABLE_WITHDRAW
 extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
 
+static inline pgtable_t __pgtable_trans_huge_withdraw(struct mm_struct *mm,
+						      pmd_t *pmdp, int tozero)
+{
+	return pgtable_trans_huge_withdraw(mm, pmdp);
+}
+
 static inline int pmd_trans_splitting(pmd_t pmd)
 {
 	return pmd_val(pmd) & _SEGMENT_ENTRY_SPLIT;
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 4c86de2..0f57c61 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -858,6 +858,12 @@ extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 
 #define __HAVE_ARCH_PGTABLE_WITHDRAW
 extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
+
+static inline pgtable_t __pgtable_trans_huge_withdraw(struct mm_struct *mm,
+						      pmd_t *pmdp, int tozero)
+{
+	return pgtable_trans_huge_withdraw(mm, pmdp);
+}
 #endif
 
 /* Encode and de-code a swap entry */
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 6f87e9e..802eccc 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -169,6 +169,15 @@ extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 
 #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW
 extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
+/*
+ * Some archs use the deposited huge table internally. Request for a
+ * zeroed/non-zeroed pgtabled when withdrawing
+ */
+static inline pgtable_t __pgtable_trans_huge_withdraw(struct mm_struct *mm,
+						      pmd_t *pmdp, int tozero)
+{
+	return pgtable_trans_huge_withdraw(mm, pmdp);
+}
 #endif
 
 #ifndef __HAVE_ARCH_PMDP_INVALIDATE
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e91b763..2586994 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1380,7 +1380,12 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		struct page *page;
 		pgtable_t pgtable;
 		pmd_t orig_pmd;
-		pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
+		/*
+		 * Withdraw the pgtable without zero out, because
+		 * the following pmd_get_and_clear will look at
+		 * pgtable contents, in case of architectures like ppc64
+		 */
+		pgtable = __pgtable_trans_huge_withdraw(tlb->mm, pmd, 0);
 		orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
 		tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
 		if (is_huge_zero_pmd(orig_pmd)) {
-- 
1.7.10

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