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From:   Ankur Arora <ankur.a.arora@oracle.com>
To:     linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org
Cc:     torvalds@linux-foundation.org, akpm@linux-foundation.org,
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        konrad.wilk@oracle.com, joao.martins@oracle.com,
        ankur.a.arora@oracle.com
Subject: [PATCH v3 03/21] clear_page: add generic clear_user_pages()
Date:   Mon,  6 Jun 2022 20:20:51 +0000
Message-Id: <20220606202109.1306034-4-ankur.a.arora@oracle.com>
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Add generic clear_user_pages() which operates on contiguous
PAGE_SIZE'd chunks via an arch defined primitive.

The generic version defines:
  #define ARCH_MAX_CLEAR_PAGES_ORDER	0
so clear_user_pages() would fallback to clear_user_page().

An arch can expose this by defining __HAVE_ARCH_CLEAR_USER_PAGES.

Also add clear_user_highpages() which, either funnels through
to clear_user_pages() or does the clearing page-at-a-time.

Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---

Notes:
    1. I'm not sure that a new header asm-generic/clear_page.h is ideal.
    
    The logical place for this is asm-generic/page.h itself. However, only
    H8300 includes that and so this (and the next few patches) would need
    a stub everywhere else.
    (Just rechecked and looks like arch/h8300 is no more.)
    
    If adding a new header looks reasonable to the community, I'm happy
    to move clear_user_page(), copy_user_page() stubs out to this file.
    (Note that patches further on add non-caching clear_user_pages()
     as well.)
    
    Or, if asm-generic/page.h is the best place, then add stubs
    everywhere else.
    
    2. Shoehorning a multiple page operation in CONFIG_HIGHMEM seems
    ugly but, seemed like the best choice of a bad set of options.
    Is there a better way of doing this?

 arch/alpha/include/asm/page.h      |  1 +
 arch/arc/include/asm/page.h        |  1 +
 arch/arm/include/asm/page.h        |  1 +
 arch/arm64/include/asm/page.h      |  1 +
 arch/csky/include/asm/page.h       |  1 +
 arch/hexagon/include/asm/page.h    |  1 +
 arch/ia64/include/asm/page.h       |  1 +
 arch/m68k/include/asm/page.h       |  1 +
 arch/microblaze/include/asm/page.h |  1 +
 arch/mips/include/asm/page.h       |  1 +
 arch/nios2/include/asm/page.h      |  2 ++
 arch/openrisc/include/asm/page.h   |  1 +
 arch/parisc/include/asm/page.h     |  1 +
 arch/powerpc/include/asm/page.h    |  1 +
 arch/riscv/include/asm/page.h      |  1 +
 arch/s390/include/asm/page.h       |  1 +
 arch/sh/include/asm/page.h         |  1 +
 arch/sparc/include/asm/page_32.h   |  1 +
 arch/sparc/include/asm/page_64.h   |  1 +
 arch/um/include/asm/page.h         |  1 +
 arch/x86/include/asm/page.h        |  1 +
 arch/xtensa/include/asm/page.h     |  1 +
 include/asm-generic/clear_page.h   | 44 ++++++++++++++++++++++++++++++
 include/asm-generic/page.h         |  1 +
 include/linux/highmem.h            | 23 ++++++++++++++++
 25 files changed, 91 insertions(+)
 create mode 100644 include/asm-generic/clear_page.h

diff --git a/arch/alpha/include/asm/page.h b/arch/alpha/include/asm/page.h
index 8f3f5eecba28..2d3b099e165c 100644
--- a/arch/alpha/include/asm/page.h
+++ b/arch/alpha/include/asm/page.h
@@ -93,5 +93,6 @@ typedef struct page *pgtable_t;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _ALPHA_PAGE_H */
diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
index 9a62e1d87967..abdbef6897bf 100644
--- a/arch/arc/include/asm/page.h
+++ b/arch/arc/include/asm/page.h
@@ -133,6 +133,7 @@ extern int pfn_valid(unsigned long pfn);
 
 #include <asm-generic/memory_model.h>   /* page_to_pfn, pfn_to_page */
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
index 5fcc8a600e36..ba244baca1fa 100644
--- a/arch/arm/include/asm/page.h
+++ b/arch/arm/include/asm/page.h
@@ -167,5 +167,6 @@ extern int pfn_valid(unsigned long);
 #define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_TSK_EXEC
 
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif
diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index 993a27ea6f54..8407ac2b5d68 100644
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h
@@ -50,5 +50,6 @@ int pfn_is_map_memory(unsigned long pfn);
 #define VM_DATA_DEFAULT_FLAGS	(VM_DATA_FLAGS_TSK_EXEC | VM_MTE_ALLOWED)
 
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif
diff --git a/arch/csky/include/asm/page.h b/arch/csky/include/asm/page.h
index ed7451478b1b..47cc27d4ede1 100644
--- a/arch/csky/include/asm/page.h
+++ b/arch/csky/include/asm/page.h
@@ -89,6 +89,7 @@ extern unsigned long va_pa_offset;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* !__ASSEMBLY__ */
 #endif /* __ASM_CSKY_PAGE_H */
diff --git a/arch/hexagon/include/asm/page.h b/arch/hexagon/include/asm/page.h
index 7cbf719c578e..e7a8edd6903a 100644
--- a/arch/hexagon/include/asm/page.h
+++ b/arch/hexagon/include/asm/page.h
@@ -142,6 +142,7 @@ static inline void clear_page(void *page)
 #include <asm-generic/memory_model.h>
 /* XXX Todo: implement assembly-optimized version of getorder. */
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* ifdef __ASSEMBLY__ */
 #endif /* ifdef __KERNEL__ */
diff --git a/arch/ia64/include/asm/page.h b/arch/ia64/include/asm/page.h
index 1b990466d540..1feae333e250 100644
--- a/arch/ia64/include/asm/page.h
+++ b/arch/ia64/include/asm/page.h
@@ -96,6 +96,7 @@ do {						\
 #define virt_addr_valid(kaddr)	pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
 
 #include <asm-generic/memory_model.h>
+#include <asm-generic/clear_page.h>
 
 #ifdef CONFIG_FLATMEM
 # define pfn_valid(pfn)		((pfn) < max_mapnr)
diff --git a/arch/m68k/include/asm/page.h b/arch/m68k/include/asm/page.h
index 2f1c54e4725d..1aeaae820670 100644
--- a/arch/m68k/include/asm/page.h
+++ b/arch/m68k/include/asm/page.h
@@ -68,5 +68,6 @@ extern unsigned long _ramend;
 #endif
 
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _M68K_PAGE_H */
diff --git a/arch/microblaze/include/asm/page.h b/arch/microblaze/include/asm/page.h
index 4b8b2fa78fc5..baa03569477a 100644
--- a/arch/microblaze/include/asm/page.h
+++ b/arch/microblaze/include/asm/page.h
@@ -137,5 +137,6 @@ extern int page_is_ram(unsigned long pfn);
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _ASM_MICROBLAZE_PAGE_H */
diff --git a/arch/mips/include/asm/page.h b/arch/mips/include/asm/page.h
index 96bc798c1ec1..3dde03bf99f3 100644
--- a/arch/mips/include/asm/page.h
+++ b/arch/mips/include/asm/page.h
@@ -269,5 +269,6 @@ static inline unsigned long kaslr_offset(void)
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _ASM_PAGE_H */
diff --git a/arch/nios2/include/asm/page.h b/arch/nios2/include/asm/page.h
index 6a989819a7c1..9763048bd3ed 100644
--- a/arch/nios2/include/asm/page.h
+++ b/arch/nios2/include/asm/page.h
@@ -104,6 +104,8 @@ static inline bool pfn_valid(unsigned long pfn)
 
 #include <asm-generic/getorder.h>
 
+#include <asm-generic/clear_page.h>
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* _ASM_NIOS2_PAGE_H */
diff --git a/arch/openrisc/include/asm/page.h b/arch/openrisc/include/asm/page.h
index aab6e64d6db4..879419c00cd4 100644
--- a/arch/openrisc/include/asm/page.h
+++ b/arch/openrisc/include/asm/page.h
@@ -88,5 +88,6 @@ typedef struct page *pgtable_t;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* __ASM_OPENRISC_PAGE_H */
diff --git a/arch/parisc/include/asm/page.h b/arch/parisc/include/asm/page.h
index 6faaaa3ebe9b..961f88d6ff63 100644
--- a/arch/parisc/include/asm/page.h
+++ b/arch/parisc/include/asm/page.h
@@ -184,6 +184,7 @@ extern int npmem_ranges;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 #include <asm/pdc.h>
 
 #define PAGE0   ((struct zeropage *)absolute_pointer(__PAGE_OFFSET))
diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index e5f75c70eda8..4742b1f99a3e 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -335,6 +335,7 @@ static inline unsigned long kaslr_offset(void)
 }
 
 #include <asm-generic/memory_model.h>
+#include <asm-generic/clear_page.h>
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_PAGE_H */
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 1526e410e802..ce9005ffccb0 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -188,5 +188,6 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _ASM_RISCV_PAGE_H */
diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 61dea67bb9c7..7a598f86ae39 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -207,5 +207,6 @@ int arch_make_page_accessible(struct page *page);
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _S390_PAGE_H */
diff --git a/arch/sh/include/asm/page.h b/arch/sh/include/asm/page.h
index eca5daa43b93..5e49bb342c2c 100644
--- a/arch/sh/include/asm/page.h
+++ b/arch/sh/include/asm/page.h
@@ -176,6 +176,7 @@ typedef struct page *pgtable_t;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 /*
  * Some drivers need to perform DMA into kmalloc'ed buffers
diff --git a/arch/sparc/include/asm/page_32.h b/arch/sparc/include/asm/page_32.h
index fff8861df107..2f061d9a5a30 100644
--- a/arch/sparc/include/asm/page_32.h
+++ b/arch/sparc/include/asm/page_32.h
@@ -135,5 +135,6 @@ extern unsigned long pfn_base;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _SPARC_PAGE_H */
diff --git a/arch/sparc/include/asm/page_64.h b/arch/sparc/include/asm/page_64.h
index 254dffd85fb1..2026bf92e3e7 100644
--- a/arch/sparc/include/asm/page_64.h
+++ b/arch/sparc/include/asm/page_64.h
@@ -159,5 +159,6 @@ extern unsigned long PAGE_OFFSET;
 #endif /* !(__ASSEMBLY__) */
 
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* _SPARC64_PAGE_H */
diff --git a/arch/um/include/asm/page.h b/arch/um/include/asm/page.h
index 95af12e82a32..79768ad6069c 100644
--- a/arch/um/include/asm/page.h
+++ b/arch/um/include/asm/page.h
@@ -113,6 +113,7 @@ extern unsigned long uml_physmem;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif	/* __ASSEMBLY__ */
 
diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index 9cc82f305f4b..5a246a2a66aa 100644
--- a/arch/x86/include/asm/page.h
+++ b/arch/x86/include/asm/page.h
@@ -85,6 +85,7 @@ static __always_inline u64 __is_canonical_address(u64 vaddr, u8 vaddr_bits)
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
 
diff --git a/arch/xtensa/include/asm/page.h b/arch/xtensa/include/asm/page.h
index 493eb7083b1a..2812f2bea844 100644
--- a/arch/xtensa/include/asm/page.h
+++ b/arch/xtensa/include/asm/page.h
@@ -200,4 +200,5 @@ static inline unsigned long ___pa(unsigned long va)
 #endif /* __ASSEMBLY__ */
 
 #include <asm-generic/memory_model.h>
+#include <asm-generic/clear_page.h>
 #endif /* _XTENSA_PAGE_H */
diff --git a/include/asm-generic/clear_page.h b/include/asm-generic/clear_page.h
new file mode 100644
index 000000000000..f827d661519c
--- /dev/null
+++ b/include/asm-generic/clear_page.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_GENERIC_CLEAR_PAGE_H
+#define __ASM_GENERIC_CLEAR_PAGE_H
+
+/*
+ * clear_user_pages() operates on contiguous pages and does the clearing
+ * operation in a single arch defined primitive.
+ *
+ * To do this, arch code defines clear_user_pages() and the max granularity
+ * it can handle via ARCH_MAX_CLEAR_PAGES_ORDER.
+ *
+ * Note that given the need for contiguity, __HAVE_ARCH_CLEAR_USER_PAGES
+ * and CONFIG_HIGHMEM are mutually exclusive.
+ */
+
+#if defined(CONFIG_HIGHMEM) && defined(__HAVE_ARCH_CLEAR_USER_PAGES)
+#error CONFIG_HIGHMEM is incompatible with __HAVE_ARCH_CLEAR_USER_PAGES
+#endif
+
+#ifndef __HAVE_ARCH_CLEAR_USER_PAGES
+
+/*
+ * For architectures that do not expose __HAVE_ARCH_CLEAR_USER_PAGES, set
+ * the granularity to be identical to clear_user_page().
+ */
+#define ARCH_MAX_CLEAR_PAGES_ORDER	0
+
+#ifndef __ASSEMBLY__
+
+/*
+ * With ARCH_MAX_CLEAR_PAGES_ORDER == 0, all callers should be specifying
+ * npages == 1 and so we just fallback to clear_user_page().
+ */
+static inline void clear_user_pages(void *page, unsigned long vaddr,
+			       struct page *start_page, unsigned int npages)
+{
+	clear_user_page(page, vaddr, start_page);
+}
+#endif /* __ASSEMBLY__ */
+#endif /* __HAVE_ARCH_CLEAR_USER_PAGES */
+
+#define ARCH_MAX_CLEAR_PAGES	(1 << ARCH_MAX_CLEAR_PAGES_ORDER)
+
+#endif /* __ASM_GENERIC_CLEAR_PAGE_H */
diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h
index 6fc47561814c..060094e7f964 100644
--- a/include/asm-generic/page.h
+++ b/include/asm-generic/page.h
@@ -93,5 +93,6 @@ extern unsigned long memory_end;
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
+#include <asm-generic/clear_page.h>
 
 #endif /* __ASM_GENERIC_PAGE_H */
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 3af34de54330..08781d7693e7 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -208,6 +208,29 @@ static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
 }
 #endif
 
+#ifdef __HAVE_ARCH_CLEAR_USER_PAGES
+static inline void clear_user_highpages(struct page *page, unsigned long vaddr,
+					unsigned int npages)
+{
+	void *addr = page_address(page);
+
+	clear_user_pages(addr, vaddr, page, npages);
+}
+#else
+static inline void clear_user_highpages(struct page *page, unsigned long vaddr,
+					unsigned int npages)
+{
+	void *addr;
+	unsigned int i;
+
+	for (i = 0; i < npages; i++, page++, vaddr += PAGE_SIZE) {
+		addr = kmap_local_page(page);
+		clear_user_page(addr, vaddr, page);
+		kunmap_local(addr);
+	}
+}
+#endif /* __HAVE_ARCH_CLEAR_USER_PAGES */
+
 #ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
 /**
  * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM page for a VMA that the caller knows can move
-- 
2.31.1