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Date: Thu, 30 Apr 2015 13:55:41 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: akpm@...ux-foundation.org, paulus@...ba.org,
benh@...nel.crashing.org, kirill.shutemov@...ux.intel.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [RFC PATCH 3/3] mm/thp: Add new function to clear pmd on collapse
Some arch may need an explicit IPI when clearing pmd
on collapse. Add new function which arch can override.
After this pmdp_clear_flush is used only for THP case
to invalidate a huge page pte.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
arch/powerpc/include/asm/pgtable-ppc64.h | 4 ++
arch/powerpc/mm/pgtable_64.c | 77 ++++++++++++++++----------------
include/asm-generic/pgtable.h | 9 ++++
mm/huge_memory.c | 2 +-
4 files changed, 53 insertions(+), 39 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index ff275443a040..655dde8e9683 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -562,6 +562,10 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
extern void pmdp_splitting_flush_notify(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);
+#define __HAVE_ARCH_PMDP_COLLAPSE_FLUSH
+extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmdp);
+
#define __HAVE_ARCH_PGTABLE_DEPOSIT
extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
pgtable_t pgtable);
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 89b356250be3..fa49e2ff042b 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -558,45 +558,9 @@ unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)
{
- pmd_t pmd;
-
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- if (pmd_trans_huge(*pmdp)) {
- pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
- } else {
- /*
- * khugepaged calls this for normal pmd
- */
- pmd = *pmdp;
- pmd_clear(pmdp);
- /*
- * Wait for all pending hash_page to finish. This is needed
- * in case of subpage collapse. When we collapse normal pages
- * to hugepage, we first clear the pmd, then invalidate all
- * the PTE entries. The assumption here is that any low level
- * page fault will see a none pmd and take the slow path that
- * will wait on mmap_sem. But we could very well be in a
- * hash_page with local ptep pointer value. Such a hash page
- * can result in adding new HPTE entries for normal subpages.
- * That means we could be modifying the page content as we
- * copy them to a huge page. So wait for parallel hash_page
- * to finish before invalidating HPTE entries. We can do this
- * by sending an IPI to all the cpus and executing a dummy
- * function there.
- */
- kick_all_cpus_sync();
- /*
- * Now invalidate the hpte entries in the range
- * covered by pmd. This make sure we take a
- * fault and will find the pmd as none, which will
- * result in a major fault which takes mmap_sem and
- * hence wait for collapse to complete. Without this
- * the __collapse_huge_page_copy can result in copying
- * the old content.
- */
- flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
- }
- return pmd;
+ VM_BUG_ON(!pmd_trans_huge(*pmdp));
+ return pmdp_get_and_clear(vma->vm_mm, address, pmdp);
}
int pmdp_test_and_clear_young(struct vm_area_struct *vma,
@@ -641,6 +605,43 @@ void pmdp_splitting_flush_notify(struct vm_area_struct *vma,
kick_all_cpus_sync();
}
+pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmdp)
+{
+ pmd_t pmd;
+
+ VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+ pmd = *pmdp;
+ pmd_clear(pmdp);
+ /*
+ * Wait for all pending hash_page to finish. This is needed
+ * in case of subpage collapse. When we collapse normal pages
+ * to hugepage, we first clear the pmd, then invalidate all
+ * the PTE entries. The assumption here is that any low level
+ * page fault will see a none pmd and take the slow path that
+ * will wait on mmap_sem. But we could very well be in a
+ * hash_page with local ptep pointer value. Such a hash page
+ * can result in adding new HPTE entries for normal subpages.
+ * That means we could be modifying the page content as we
+ * copy them to a huge page. So wait for parallel hash_page
+ * to finish before invalidating HPTE entries. We can do this
+ * by sending an IPI to all the cpus and executing a dummy
+ * function there.
+ */
+ kick_all_cpus_sync();
+ /*
+ * Now invalidate the hpte entries in the range
+ * covered by pmd. This make sure we take a
+ * fault and will find the pmd as none, which will
+ * result in a major fault which takes mmap_sem and
+ * hence wait for collapse to complete. Without this
+ * the __collapse_huge_page_copy can result in copying
+ * the old content.
+ */
+ flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
+ return pmd;
+}
+
/*
* We want to put the pgtable in pmd and use pgtable for tracking
* the base page size hptes
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index d091a666f5b1..2e1e4653ae7c 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -189,6 +189,15 @@ extern void pmdp_splitting_flush_notify(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);
#endif
+#ifndef __HAVE_ARCH_PMDP_COLLAPSE_FLUSH
+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);
+}
+#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 81e9578bf43a..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);
--
2.1.4
--
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