[PATCHv6 21/36] s390, thp: remove infrastructure for handling splitting PMDs

Kirill A. Shutemov
2015-06-03T17:15:15Z

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/s390/include/asm/pgtable.h | 15 +--------------
arch/s390/mm/gup.c | 11 +----------
arch/s390/mm/pgtable.c | 16 ----------------
3 files changed, 2 insertions(+), 40 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index cf7e7c6bab9d..06bf2f1367f9 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -380,7 +380,6 @@ static inline int is_module_addr(void *addr)

#define _SEGMENT_ENTRY_DIRTY 0x2000 /* SW segment dirty bit */
#define _SEGMENT_ENTRY_YOUNG 0x1000 /* SW segment young bit */
-#define _SEGMENT_ENTRY_SPLIT 0x0800 /* THP splitting bit */
#define _SEGMENT_ENTRY_LARGE 0x0400 /* STE-format control, large page */
#define _SEGMENT_ENTRY_READ 0x0002 /* SW segment read bit */
#define _SEGMENT_ENTRY_WRITE 0x0001 /* SW segment write bit */
@@ -404,8 +403,6 @@ static inline int is_module_addr(void *addr)
* read-write, old segment table entries (origin!=0)
*/

-#define _SEGMENT_ENTRY_SPLIT_BIT 11 /* THP splitting bit number */
-
/* Page status table bits for virtualization */
#define PGSTE_ACC_BITS 0xf000000000000000UL
#define PGSTE_FP_BIT 0x0800000000000000UL
@@ -617,10 +614,6 @@ static inline int pmd_bad(pmd_t pmd)
return (pmd_val(pmd) & ~_SEGMENT_ENTRY_BITS) != 0;
}

-#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
-extern void pmdp_splitting_flush(struct vm_area_struct *vma,
- unsigned long addr, pmd_t *pmdp);
-
#define __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
extern int pmdp_set_access_flags(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp,
@@ -1494,7 +1487,7 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
if (pmd_large(pmd)) {
pmd_val(pmd) &= _SEGMENT_ENTRY_ORIGIN_LARGE |
_SEGMENT_ENTRY_DIRTY | _SEGMENT_ENTRY_YOUNG |
- _SEGMENT_ENTRY_LARGE | _SEGMENT_ENTRY_SPLIT;
+ _SEGMENT_ENTRY_LARGE;
pmd_val(pmd) |= massage_pgprot_pmd(newprot);
if (!(pmd_val(pmd) & _SEGMENT_ENTRY_DIRTY))
pmd_val(pmd) |= _SEGMENT_ENTRY_PROTECT;
@@ -1602,12 +1595,6 @@ 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 int pmd_trans_splitting(pmd_t pmd)
-{
- return (pmd_val(pmd) & _SEGMENT_ENTRY_LARGE) &&
- (pmd_val(pmd) & _SEGMENT_ENTRY_SPLIT);
-}
-
static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp, pmd_t entry)
{
diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index dab30527ad41..83eb4629bdb2 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -104,16 +104,7 @@ static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
pmd = *pmdp;
barrier();
next = pmd_addr_end(addr, end);
- /*
- * The pmd_trans_splitting() check below explains why
- * pmdp_splitting_flush() has to serialize with
- * smp_call_function() against our disabled IRQs, to stop
- * this gup-fast code from running while we set the
- * splitting bit in the pmd. Returning zero will take
- * the slow path that will call wait_split_huge_page()
- * if the pmd is still in splitting state.
- */
- if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+ if (pmd_none(pmd))
return 0;
if (unlikely(pmd_large(pmd))) {
if (!gup_huge_pmd(pmdp, pmd, addr, next,
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index b2c1542f2ba2..5736232f7936 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -1419,22 +1419,6 @@ int pmdp_set_access_flags(struct vm_area_struct *vma,
return 1;
}

-static void pmdp_splitting_flush_sync(void *arg)
-{
- /* Simply deliver the interrupt */
-}
-
-void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
- pmd_t *pmdp)
-{
- VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- if (!test_and_set_bit(_SEGMENT_ENTRY_SPLIT_BIT,
- (unsigned long *) pmdp)) {
- /* need to serialize against gup-fast (IRQ disabled) */
- smp_call_function(pmdp_splitting_flush_sync, NULL, 1);
- }
-}
-
void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
pgtable_t pgtable)
{
--
2.1.4