linux-kernel - [PATCH V2 1/2] mm/thp: Use new functions to clear pmd on splitting and collapse

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Date:	Fri,  1 May 2015 11:13:25 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	akpm@...ux-foundation.org, mpe@...erman.id.au, paulus@...ba.org,
	benh@...nel.crashing.org, kirill.shutemov@...ux.intel.com
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH V2 1/2] mm/thp: Use new functions to clear pmd on splitting and collapse

Some arch may require an explicit IPI before a THP PMD split or
collapse. This enable us to use local_irq_disable to prevent
a parallel THP PMD split or collapse.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 include/asm-generic/pgtable.h | 32 ++++++++++++++++++++++++++++++++
 mm/huge_memory.c              |  9 +++++----
 2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index fe617b7e4be6..e95c697bef25 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -184,6 +184,38 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
+#ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH_NOTIFY
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#define pmdp_splitting_flush_notify pmdp_clear_flush_notify
+#else
+static inline void pmdp_splitting_flush_notify(struct vm_area_struct *vma,
+					       unsigned long address,
+					       pmd_t *pmdp)
+{
+	BUILD_BUG();
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif
+
+#ifndef __HAVE_ARCH_PMDP_COLLAPSE_FLUSH
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+				       unsigned long address,
+				       pmd_t *pmdp)
+{
+	return pmdp_clear_flush(vma, address, pmdp);
+}
+#else
+static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+				       unsigned long address,
+				       pmd_t *pmdp)
+{
+	BUILD_BUG();
+	return __pmd(0);
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif
+
 #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
 extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 				       pgtable_t pgtable);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index cce4604c192f..30c1b46fcf6d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2187,7 +2187,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 	 * huge and small TLB entries for the same virtual address
 	 * to avoid the risk of CPU bugs in that area.
 	 */
-	_pmd = pmdp_clear_flush(vma, address, pmd);
+	_pmd = pmdp_collapse_flush(vma, address, pmd);
 	spin_unlock(pmd_ptl);
 	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 
@@ -2606,9 +2606,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 
 	write = pmd_write(*pmd);
 	young = pmd_young(*pmd);
-
-	/* leave pmd empty until pte is filled */
-	pmdp_clear_flush_notify(vma, haddr, pmd);
+	/*
+	 * leave pmd empty until pte is filled.
+	 */
+	pmdp_splitting_flush_notify(vma, haddr, pmd);
 
 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
 	pmd_populate(mm, &_pmd, pgtable);
-- 
2.1.4

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