linux-kernel - [PATCH v1 04/14] arm64/mm: ptep_get_and_clear(): New layer to manage contig bit

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Date:   Thu, 22 Jun 2023 15:41:59 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Matthew Wilcox <willy@...radead.org>,
        Yu Zhao <yuzhao@...gle.com>,
        Mark Rutland <mark.rutland@....com>
Cc:     Ryan Roberts <ryan.roberts@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH v1 04/14] arm64/mm: ptep_get_and_clear(): New layer to manage contig bit

Create a new layer for the in-table PTE manipulation APIs. For now, The
existing API is prefixed with double underscore to become the
arch-private API and the public API is just a simple wrapper that calls
the private API.

The public API implementation will subsequently be used to transparently
manipulate the contiguous bit where appropriate. But since there are
already some contig-aware users (e.g. hugetlb, kernel mapper), we must
first ensure those users use the private API directly so that the future
contig-bit manipulations in the public API do not interfere with those
existing uses.

No behavioural changes intended.

Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
 arch/arm64/include/asm/pgtable.h | 10 ++++++++--
 arch/arm64/mm/hugetlbpage.c      |  4 ++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 06b5dca469f5..2a525e72537d 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -941,8 +941,7 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
-#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
-static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
+static inline pte_t __ptep_get_and_clear(struct mm_struct *mm,
 				       unsigned long address, pte_t *ptep)
 {
 	pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0));
@@ -1146,6 +1145,13 @@ static inline void pte_clear(struct mm_struct *mm,
 	__pte_clear(mm, addr, ptep);
 }
 
+#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
+static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
+				unsigned long addr, pte_t *ptep)
+{
+	return __ptep_get_and_clear(mm, addr, ptep);
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_PGTABLE_H */
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index eebd3107c7d2..931a17f3c3fb 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -188,7 +188,7 @@ static pte_t get_clear_contig(struct mm_struct *mm,
 	unsigned long i;
 
 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
-		pte_t pte = ptep_get_and_clear(mm, addr, ptep);
+		pte_t pte = __ptep_get_and_clear(mm, addr, ptep);
 
 		/*
 		 * If HW_AFDBM is enabled, then the HW could turn on
@@ -429,7 +429,7 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 	pte_t orig_pte = ptep_get(ptep);
 
 	if (!pte_cont(orig_pte))
-		return ptep_get_and_clear(mm, addr, ptep);
+		return __ptep_get_and_clear(mm, addr, ptep);
 
 	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
 
-- 
2.25.1