powerpc/nohash: Refactor checking of no-change in pte_update()

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.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/076563e611c2b51036686a8d378bfd5ef1726341.1695659959.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
index b149a39f26853eec2de0e63983ee6fc476812b62..cba08a62c52cd549f71b36898a9e7e650ca6f30d 100644 (file)
--- 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 bd5c3a4baabd058ffded387bfd926a560aa3a699..8adaacbbdd1d6606574c3db0776e39b4cdccae61 100644 (file)
--- 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))