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Message-ID: <47323ad1daf0bc390ed2ce4f08b303bab672bd3c.1694443576.git.christophe.leroy@csgroup.eu>
Date: Mon, 11 Sep 2023 21:03:19 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 13/19] 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@...roup.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
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