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

Aneesh Kumar K.V
2015-05-01T05:43:55Z

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@linux.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