[PATCHv6 20/36] powerpc, thp: remove infrastructure for handling splitting PMDs

Kirill A. Shutemov
2015-06-03T17:19:45Z

With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.

pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as
needed for fast_gup.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/powerpc/include/asm/kvm_book3s_64.h | 6 ----
arch/powerpc/include/asm/pgtable-ppc64.h | 25 +---------------
arch/powerpc/mm/hugepage-hash64.c | 3 --
arch/powerpc/mm/hugetlbpage.c | 7 +----
arch/powerpc/mm/pgtable_64.c | 49 --------------------------------
5 files changed, 2 insertions(+), 88 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index 2d81e202bdcc..9a96fe3caa48 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -298,12 +298,6 @@ static inline pte_t kvmppc_read_update_linux_pte(pte_t *ptep, int writing,
cpu_relax();
continue;
}
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- /* If hugepage and is trans splitting return None */
- if (unlikely(hugepage &&
- pmd_trans_splitting(pte_pmd(old_pte))))
- return __pte(0);
-#endif
/* If pte is not present return None */
if (unlikely(!(old_pte & _PAGE_PRESENT)))
return __pte(0);
diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index 012e3adab7f8..5729b303d206 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -358,11 +358,6 @@ void pgtable_cache_init(void);
#endif /* __ASSEMBLY__ */

/*
- * THP pages can't be special. So use the _PAGE_SPECIAL
- */
-#define _PAGE_SPLITTING _PAGE_SPECIAL
-
-/*
* We need to differentiate between explicit huge page and THP huge
* page, since THP huge page also need to track real subpage details
*/
@@ -372,8 +367,7 @@ void pgtable_cache_init(void);
* set of bits not changed in pmd_modify.
*/
#define _HPAGE_CHG_MASK (PTE_RPN_MASK | _PAGE_HPTEFLAGS | \
- _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_SPLITTING | \
- _PAGE_THP_HUGE)
+ _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_THP_HUGE)

#ifndef __ASSEMBLY__
/*
@@ -455,13 +449,6 @@ static inline int pmd_trans_huge(pmd_t pmd)
return (pmd_val(pmd) & 0x3) && (pmd_val(pmd) & _PAGE_THP_HUGE);
}

-static inline int pmd_trans_splitting(pmd_t pmd)
-{
- if (pmd_trans_huge(pmd))
- return pmd_val(pmd) & _PAGE_SPLITTING;
- return 0;
-}
-
extern int has_transparent_hugepage(void);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

@@ -514,12 +501,6 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
return pmd;
}

-static inline pmd_t pmd_mksplitting(pmd_t pmd)
-{
- pmd_val(pmd) |= _PAGE_SPLITTING;
- return pmd;
-}
-
#define __HAVE_ARCH_PMD_SAME
static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
{
@@ -570,10 +551,6 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
pmd_hugepage_update(mm, addr, pmdp, _PAGE_RW, 0);
}

-#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
-extern void pmdp_splitting_flush(struct vm_area_struct *vma,
- unsigned long address, pmd_t *pmdp);
-
#define pmdp_collapse_flush pmdp_collapse_flush
extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);
diff --git a/arch/powerpc/mm/hugepage-hash64.c b/arch/powerpc/mm/hugepage-hash64.c
index 86686514ae13..078f7207afd2 100644
--- a/arch/powerpc/mm/hugepage-hash64.c
+++ b/arch/powerpc/mm/hugepage-hash64.c
@@ -39,9 +39,6 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
/* If PMD busy, retry the access */
if (unlikely(old_pmd & _PAGE_BUSY))
return 0;
- /* If PMD is trans splitting retry the access */
- if (unlikely(old_pmd & _PAGE_SPLITTING))
- return 0;
/* If PMD permissions don't match, take page fault */
if (unlikely(access & ~old_pmd))
return 1;
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 5f979e51ef7b..a09ff52b906e 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -997,13 +997,8 @@ pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift
/*
* A hugepage collapse is captured by pmd_none, because
* it mark the pmd none and do a hpte invalidate.
- *
- * A hugepage split is captured by pmd_trans_splitting
- * because we mark the pmd trans splitting and do a
- * hpte invalidate
- *
*/
- if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+ if (pmd_none(pmd))
return NULL;

if (pmd_huge(pmd) || pmd_large(pmd)) {
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 52c4827bceb0..7bad475bc235 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -614,55 +614,6 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,
}

/*
- * We mark the pmd splitting and invalidate all the hpte
- * entries for this hugepage.
- */
-void pmdp_splitting_flush(struct vm_area_struct *vma,
- unsigned long address, pmd_t *pmdp)
-{
- unsigned long old, tmp;
-
- VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-
-#ifdef CONFIG_DEBUG_VM
- WARN_ON(!pmd_trans_huge(*pmdp));
- assert_spin_locked(&vma->vm_mm->page_table_lock);
-#endif
-
-#ifdef PTE_ATOMIC_UPDATES
-
- __asm__ __volatile__(
- "1: ldarx %0,0,%3\n\
- andi. %1,%0,%6\n\
- bne- 1b \n\
- ori %1,%0,%4 \n\
- stdcx. %1,0,%3 \n\
- bne- 1b"
- : "=&r" (old), "=&r" (tmp), "=m" (*pmdp)
- : "r" (pmdp), "i" (_PAGE_SPLITTING), "m" (*pmdp), "i" (_PAGE_BUSY)
- : "cc" );
-#else
- old = pmd_val(*pmdp);
- *pmdp = __pmd(old | _PAGE_SPLITTING);
-#endif
- /*
- * If we didn't had the splitting flag set, go and flush the
- * HPTE entries.
- */
- trace_hugepage_splitting(address, old);
- if (!(old & _PAGE_SPLITTING)) {
- /* We need to flush the hpte */
- if (old & _PAGE_HASHPTE)
- hpte_do_hugepage_flush(vma->vm_mm, address, pmdp, old);
- }
- /*
- * This ensures that generic code that rely on IRQ disabling
- * to prevent a parallel THP split work as expected.
- */
- kick_all_cpus_sync();
-}
-
-/*
* We want to put the pgtable in pmd and use pgtable for tracking
* the base page size hptes
*/
--
2.1.4