[PATCH v2 13/37] powerpc/nohash: Refactor checking of no-change in pte_update()

[Christophe Leroy]

On nohash/64, a few callers of pte_update() check if there is
really a change in order to avoid an unnecessary write.

Refactor that inside pte_update().

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
 arch/powerpc/include/asm/nohash/64/pgtable.h | 9 ---------
 arch/powerpc/include/asm/nohash/pgtable.h    | 3 +++
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h 
b/arch/powerpc/include/asm/nohash/64/pgtable.h
index b149a39f2685..cba08a62c52c 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
@@ -181,8 +181,6 @@ static inline int __ptep_test_and_clear_young(struct 
mm_struct *mm,
 {
        unsigned long old;
 
-       if (!pte_young(*ptep))
-               return 0;
        old = pte_update(mm, addr, ptep, _PAGE_ACCESSED, 0, 0);
        return (old & _PAGE_ACCESSED) != 0;
 }
@@ -198,10 +196,6 @@ static inline int __ptep_test_and_clear_young(struct 
mm_struct *mm,
 static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
                                      pte_t *ptep)
 {
-
-       if ((pte_val(*ptep) & _PAGE_RW) == 0)
-               return;
-
        pte_update(mm, addr, ptep, _PAGE_RW, 0, 0);
 }
 
@@ -209,9 +203,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, 
unsigned long addr,
 static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
                                           unsigned long addr, pte_t *ptep)
 {
-       if ((pte_val(*ptep) & _PAGE_RW) == 0)
-               return;
-
        pte_update(mm, addr, ptep, _PAGE_RW, 0, 1);
 }
 
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h 
b/arch/powerpc/include/asm/nohash/pgtable.h
index bd5c3a4baabd..8adaacbbdd1d 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -47,6 +47,9 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, 
unsigned long addr, p
        pte_basic_t old = pte_val(*p);
        pte_basic_t new = (old & ~(pte_basic_t)clr) | set;
 
+       if (new == old)
+               return old;
+
        *p = __pte(new);
 
        if (IS_ENABLED(CONFIG_44x) && (old & _PAGE_USER) && (old & _PAGE_EXEC))
-- 
2.41.0