[PATCH v3 0/2] move __HAVE_ARCH_PTE_SPECIAL in Kconfig

[PATCH v3 0/2] move __HAVE_ARCH_PTE_SPECIAL in Kconfig

[Laurent Dufour]

The per architecture __HAVE_ARCH_PTE_SPECIAL is defined statically in the
per architecture header files. This doesn't allow to make other
configuration dependent on it.

The first patch of this series is replacing __HAVE_ARCH_PTE_SPECIAL by
CONFIG_ARCH_HAS_PTE_SPECIAL defined into the Kconfig files,
setting it automatically when architectures was already setting it in
header file.

The second patch is removing the odd define HAVE_PTE_SPECIAL which is a
duplicate of CONFIG_ARCH_HAS_PTE_SPECIAL.

There is no functional change introduced by this series.

--
Changes since v2:
 * remove __HAVE_ARCH_PTE_SPECIAL in arch/riscv/include/asm/pgtable-bits.h
 * use IS_ENABLED() instead of #ifdef blocks in patch 2

Laurent Dufour (2):
  mm: introduce ARCH_HAS_PTE_SPECIAL
  mm: remove odd HAVE_PTE_SPECIAL

 .../features/vm/pte_special/arch-support.txt          |  2 +-
 arch/arc/Kconfig                                      |  1 +
 arch/arc/include/asm/pgtable.h                        |  2 --
 arch/arm/Kconfig                                      |  1 +
 arch/arm/include/asm/pgtable-3level.h                 |  1 -
 arch/arm64/Kconfig                                    |  1 +
 arch/arm64/include/asm/pgtable.h                      |  2 --
 arch/powerpc/Kconfig                                  |  1 +
 arch/powerpc/include/asm/book3s/64/pgtable.h          |  3 ---
 arch/powerpc/include/asm/pte-common.h                 |  3 ---
 arch/riscv/Kconfig                                    |  1 +
 arch/riscv/include/asm/pgtable-bits.h                 |  3 ---
 arch/s390/Kconfig                                     |  1 +
 arch/s390/include/asm/pgtable.h                       |  1 -
 arch/sh/Kconfig                                       |  1 +
 arch/sh/include/asm/pgtable.h                         |  2 --
 arch/sparc/Kconfig                                    |  1 +
 arch/sparc/include/asm/pgtable_64.h                   |  3 ---
 arch/x86/Kconfig                                      |  1 +
 arch/x86/include/asm/pgtable_types.h                  |  1 -
 include/linux/pfn_t.h                                 |  4 ++--
 mm/Kconfig                                            |  3 +++
 mm/gup.c                                              |  4 ++--
 mm/memory.c                                           | 19 ++++++++-----------
 24 files changed, 25 insertions(+), 37 deletions(-)

-- 
2.7.4

[PATCH v3 1/2] mm: introduce ARCH_HAS_PTE_SPECIAL

[Laurent Dufour]

Currently the PTE special supports is turned on in per architecture header
files. Most of the time, it is defined in arch/*/include/asm/pgtable.h
depending or not on some other per architecture static definition.

This patch introduce a new configuration variable to manage this directly
in the Kconfig files. It would later replace __HAVE_ARCH_PTE_SPECIAL.

Here notes for some architecture where the definition of
__HAVE_ARCH_PTE_SPECIAL is not obvious:

arm
 __HAVE_ARCH_PTE_SPECIAL which is currently defined in
arch/arm/include/asm/pgtable-3level.h which is included by
arch/arm/include/asm/pgtable.h when CONFIG_ARM_LPAE is set.
So select ARCH_HAS_PTE_SPECIAL if ARM_LPAE.

powerpc
__HAVE_ARCH_PTE_SPECIAL is defined in 2 files:
 - arch/powerpc/include/asm/book3s/64/pgtable.h
 - arch/powerpc/include/asm/pte-common.h
The first one is included if (PPC_BOOK3S & PPC64) while the second is
included in all the other cases.
So select ARCH_HAS_PTE_SPECIAL all the time.

sparc:
__HAVE_ARCH_PTE_SPECIAL is defined if defined(__sparc__) &&
defined(__arch64__) which are defined through the compiler in
sparc/Makefile if !SPARC32 which I assume to be if SPARC64.
So select ARCH_HAS_PTE_SPECIAL if SPARC64

There is no functional change introduced by this patch.

Suggested-by: Jerome Glisse <jglisse@redhat>
Reviewed-by: Jerome Glisse <jglisse@redhat>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
 Documentation/features/vm/pte_special/arch-support.txt | 2 +-
 arch/arc/Kconfig                                       | 1 +
 arch/arc/include/asm/pgtable.h                         | 2 --
 arch/arm/Kconfig                                       | 1 +
 arch/arm/include/asm/pgtable-3level.h                  | 1 -
 arch/arm64/Kconfig                                     | 1 +
 arch/arm64/include/asm/pgtable.h                       | 2 --
 arch/powerpc/Kconfig                                   | 1 +
 arch/powerpc/include/asm/book3s/64/pgtable.h           | 3 ---
 arch/powerpc/include/asm/pte-common.h                  | 3 ---
 arch/riscv/Kconfig                                     | 1 +
 arch/riscv/include/asm/pgtable-bits.h                  | 3 ---
 arch/s390/Kconfig                                      | 1 +
 arch/s390/include/asm/pgtable.h                        | 1 -
 arch/sh/Kconfig                                        | 1 +
 arch/sh/include/asm/pgtable.h                          | 2 --
 arch/sparc/Kconfig                                     | 1 +
 arch/sparc/include/asm/pgtable_64.h                    | 3 ---
 arch/x86/Kconfig                                       | 1 +
 arch/x86/include/asm/pgtable_types.h                   | 1 -
 include/linux/pfn_t.h                                  | 4 ++--
 mm/Kconfig                                             | 3 +++
 mm/gup.c                                               | 4 ++--
 mm/memory.c                                            | 2 +-
 24 files changed, 18 insertions(+), 27 deletions(-)

diff --git a/Documentation/features/vm/pte_special/arch-support.txt b/Documentation/features/vm/pte_special/arch-support.txt
index 055004f467d2..cd05924ea875 100644
--- a/Documentation/features/vm/pte_special/arch-support.txt
+++ b/Documentation/features/vm/pte_special/arch-support.txt
@@ -1,6 +1,6 @@
 #
 # Feature name:          pte_special
-#         Kconfig:       __HAVE_ARCH_PTE_SPECIAL
+#         Kconfig:       ARCH_HAS_PTE_SPECIAL
 #         description:   arch supports the pte_special()/pte_mkspecial() VM APIs
 #
     -----------------------
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index d76bf4a83740..8516e2b0239a 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -44,6 +44,7 @@ config ARC
 	select HAVE_GENERIC_DMA_COHERENT
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_LZMA
+	select ARCH_HAS_PTE_SPECIAL
 
 config MIGHT_HAVE_PCI
 	bool
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 08fe33830d4b..8ec5599a0957 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -320,8 +320,6 @@ PTE_BIT_FUNC(mkexec,	|= (_PAGE_EXECUTE));
 PTE_BIT_FUNC(mkspecial,	|= (_PAGE_SPECIAL));
 PTE_BIT_FUNC(mkhuge,	|= (_PAGE_HW_SZ));
 
-#define __HAVE_ARCH_PTE_SPECIAL
-
 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 {
 	return __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot));
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a7f8e7f4b88f..c088c851b235 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -8,6 +8,7 @@ config ARM
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FORTIFY_SOURCE
+	select ARCH_HAS_PTE_SPECIAL if ARM_LPAE
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_PHYS_TO_DMA
 	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index 2a4836087358..6d50a11d7793 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -219,7 +219,6 @@ static inline pte_t pte_mkspecial(pte_t pte)
 	pte_val(pte) |= L_PTE_SPECIAL;
 	return pte;
 }
-#define	__HAVE_ARCH_PTE_SPECIAL
 
 #define pmd_write(pmd)		(pmd_isclear((pmd), L_PMD_SECT_RDONLY))
 #define pmd_dirty(pmd)		(pmd_isset((pmd), L_PMD_SECT_DIRTY))
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index eb2cf4938f6d..9a3f1b1ab50c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -17,6 +17,7 @@ config ARM64
 	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
+	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_STRICT_KERNEL_RWX
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7e2c27e63cd8..b96c8a186908 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -306,8 +306,6 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b)
 #define HPAGE_MASK		(~(HPAGE_SIZE - 1))
 #define HUGETLB_PAGE_ORDER	(HPAGE_SHIFT - PAGE_SHIFT)
 
-#define __HAVE_ARCH_PTE_SPECIAL
-
 static inline pte_t pgd_pte(pgd_t pgd)
 {
 	return __pte(pgd_val(pgd));
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c32a181a7cbb..f7415fe25c07 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -141,6 +141,7 @@ config PPC
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_PHYS_TO_DMA
 	select ARCH_HAS_PMEM_API                if PPC64
+	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_MEMBARRIER_CALLBACKS
 	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE
 	select ARCH_HAS_SG_CHAIN
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 47b5ffc8715d..b3ac8948b257 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -319,9 +319,6 @@ extern unsigned long pci_io_base;
 /* Advertise special mapping type for AGP */
 #define HAVE_PAGE_AGP
 
-/* Advertise support for _PAGE_SPECIAL */
-#define __HAVE_ARCH_PTE_SPECIAL
-
 #ifndef __ASSEMBLY__
 
 /*
diff --git a/arch/powerpc/include/asm/pte-common.h b/arch/powerpc/include/asm/pte-common.h
index c4a72c7a8c83..03dfddb1f49a 100644
--- a/arch/powerpc/include/asm/pte-common.h
+++ b/arch/powerpc/include/asm/pte-common.h
@@ -216,9 +216,6 @@ static inline bool pte_user(pte_t pte)
 #define PAGE_AGP		(PAGE_KERNEL_NC)
 #define HAVE_PAGE_AGP
 
-/* Advertise support for _PAGE_SPECIAL */
-#define __HAVE_ARCH_PTE_SPECIAL
-
 #ifndef _PAGE_READ
 /* if not defined, we should not find _PAGE_WRITE too */
 #define _PAGE_READ 0
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 23d8acca5c90..92d331ea11bd 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -34,6 +34,7 @@ config RISCV
 	select THREAD_INFO_IN_TASK
 	select RISCV_TIMER
 	select GENERIC_IRQ_MULTI_HANDLER
+	select ARCH_HAS_PTE_SPECIAL
 
 config MMU
 	def_bool y
diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index 997ddbb1d370..2fa2942be221 100644
--- a/arch/riscv/include/asm/pgtable-bits.h
+++ b/arch/riscv/include/asm/pgtable-bits.h
@@ -42,7 +42,4 @@
 					  _PAGE_WRITE | _PAGE_EXEC |	\
 					  _PAGE_USER | _PAGE_GLOBAL))
 
-/* Advertise support for _PAGE_SPECIAL */
-#define __HAVE_ARCH_PTE_SPECIAL
-
 #endif /* _ASM_RISCV_PGTABLE_BITS_H */
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 32a0d5b958bf..5f1f4997e7e9 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -72,6 +72,7 @@ config S390
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
 	select ARCH_HAS_KCOV
+	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_STRICT_KERNEL_RWX
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 2d24d33bf188..9809694e1389 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -171,7 +171,6 @@ static inline int is_module_addr(void *addr)
 #define _PAGE_WRITE	0x020		/* SW pte write bit */
 #define _PAGE_SPECIAL	0x040		/* SW associated with special page */
 #define _PAGE_UNUSED	0x080		/* SW bit for pgste usage state */
-#define __HAVE_ARCH_PTE_SPECIAL
 
 #ifdef CONFIG_MEM_SOFT_DIRTY
 #define _PAGE_SOFT_DIRTY 0x002		/* SW pte soft dirty bit */
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 97fe29316476..a6c75b6806d2 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -50,6 +50,7 @@ config SUPERH
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_FUTEX_CMPXCHG if FUTEX
 	select HAVE_NMI
+	select ARCH_HAS_PTE_SPECIAL
 	help
 	  The SuperH is a RISC processor targeted for use in embedded systems
 	  and consumer electronics; it was also used in the Sega Dreamcast
diff --git a/arch/sh/include/asm/pgtable.h b/arch/sh/include/asm/pgtable.h
index 89c513a982fc..f6abfe2bca93 100644
--- a/arch/sh/include/asm/pgtable.h
+++ b/arch/sh/include/asm/pgtable.h
@@ -156,8 +156,6 @@ extern void page_table_range_init(unsigned long start, unsigned long end,
 #define HAVE_ARCH_UNMAPPED_AREA
 #define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
 
-#define __HAVE_ARCH_PTE_SPECIAL
-
 #include <asm-generic/pgtable.h>
 
 #endif /* __ASM_SH_PGTABLE_H */
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 8767e45f1b2b..6b5a4f05dcb2 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -86,6 +86,7 @@ config SPARC64
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select GENERIC_TIME_VSYSCALL
 	select ARCH_CLOCKSOURCE_DATA
+	select ARCH_HAS_PTE_SPECIAL
 
 config ARCH_DEFCONFIG
 	string
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 44d6ac47e035..1393a8ac596b 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -117,9 +117,6 @@ bool kern_addr_valid(unsigned long addr);
 #define _PAGE_PMD_HUGE    _AC(0x0100000000000000,UL) /* Huge page            */
 #define _PAGE_PUD_HUGE    _PAGE_PMD_HUGE
 
-/* Advertise support for _PAGE_SPECIAL */
-#define __HAVE_ARCH_PTE_SPECIAL
-
 /* SUN4U pte bits... */
 #define _PAGE_SZ4MB_4U	  _AC(0x6000000000000000,UL) /* 4MB Page             */
 #define _PAGE_SZ512K_4U	  _AC(0x4000000000000000,UL) /* 512K Page            */
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d8983df5a2bc..2399c8ce02be 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -57,6 +57,7 @@ config X86
 	select ARCH_HAS_KCOV			if X86_64
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_PMEM_API		if X86_64
+	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_REFCOUNT
 	select ARCH_HAS_UACCESS_FLUSHCACHE	if X86_64
 	select ARCH_HAS_SET_MEMORY
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 1e5a40673953..99fff853c944 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -65,7 +65,6 @@
 #define _PAGE_PKEY_BIT2	(_AT(pteval_t, 0))
 #define _PAGE_PKEY_BIT3	(_AT(pteval_t, 0))
 #endif
-#define __HAVE_ARCH_PTE_SPECIAL
 
 #define _PAGE_PKEY_MASK (_PAGE_PKEY_BIT0 | \
 			 _PAGE_PKEY_BIT1 | \
diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
index a03c2642a87c..21713dc14ce2 100644
--- a/include/linux/pfn_t.h
+++ b/include/linux/pfn_t.h
@@ -122,7 +122,7 @@ pud_t pud_mkdevmap(pud_t pud);
 #endif
 #endif /* __HAVE_ARCH_PTE_DEVMAP */
 
-#ifdef __HAVE_ARCH_PTE_SPECIAL
+#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
 static inline bool pfn_t_special(pfn_t pfn)
 {
 	return (pfn.val & PFN_SPECIAL) == PFN_SPECIAL;
@@ -132,5 +132,5 @@ static inline bool pfn_t_special(pfn_t pfn)
 {
 	return false;
 }
-#endif /* __HAVE_ARCH_PTE_SPECIAL */
+#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 #endif /* _LINUX_PFN_T_H_ */
diff --git a/mm/Kconfig b/mm/Kconfig
index d5004d82a1d6..1ea3e4a6a123 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -752,3 +752,6 @@ config GUP_BENCHMARK
 	  performance of get_user_pages_fast().
 
 	  See tools/testing/selftests/vm/gup_benchmark.c
+
+config ARCH_HAS_PTE_SPECIAL
+	bool
diff --git a/mm/gup.c b/mm/gup.c
index 76af4cfeaf68..d19bfbadd32a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1351,7 +1351,7 @@ static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
 	}
 }
 
-#ifdef __HAVE_ARCH_PTE_SPECIAL
+#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 			 int write, struct page **pages, int *nr)
 {
@@ -1427,7 +1427,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 {
 	return 0;
 }
-#endif /* __HAVE_ARCH_PTE_SPECIAL */
+#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 
 #if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
 static int __gup_device_huge(unsigned long pfn, unsigned long addr,
diff --git a/mm/memory.c b/mm/memory.c
index a1f990e33e38..96910c625daa 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -817,7 +817,7 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
  * PFNMAP mappings in order to support COWable mappings.
  *
  */
-#ifdef __HAVE_ARCH_PTE_SPECIAL
+#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
 # define HAVE_PTE_SPECIAL 1
 #else
 # define HAVE_PTE_SPECIAL 0
-- 
2.7.4

[PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Laurent Dufour]

Remove the additional define HAVE_PTE_SPECIAL and rely directly on
CONFIG_ARCH_HAS_PTE_SPECIAL.

There is no functional change introduced by this patch

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
 mm/memory.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 96910c625daa..7f7dc7b2a341 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -817,17 +817,12 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
  * PFNMAP mappings in order to support COWable mappings.
  *
  */
-#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
-# define HAVE_PTE_SPECIAL 1
-#else
-# define HAVE_PTE_SPECIAL 0
-#endif
 struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 			     pte_t pte, bool with_public_device)
 {
 	unsigned long pfn = pte_pfn(pte);
 
-	if (HAVE_PTE_SPECIAL) {
+	if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
 		if (likely(!pte_special(pte)))
 			goto check_pfn;
 		if (vma->vm_ops && vma->vm_ops->find_special_page)
@@ -862,7 +857,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 		return NULL;
 	}
 
-	/* !HAVE_PTE_SPECIAL case follows: */
+	/* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
 
 	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
 		if (vma->vm_flags & VM_MIXEDMAP) {
@@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 
 	if (is_zero_pfn(pfn))
 		return NULL;
-check_pfn:
+
+check_pfn: __maybe_unused
 	if (unlikely(pfn > highest_memmap_pfn)) {
 		print_bad_pte(vma, addr, pte, NULL);
 		return NULL;
@@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 	 * NOTE! We still have PageReserved() pages in the page tables.
 	 * eg. VDSO mappings can cause them to exist.
 	 */
-out:
+out: __maybe_unused
 	return pfn_to_page(pfn);
 }
 
@@ -904,7 +900,7 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
 	/*
 	 * There is no pmd_special() but there may be special pmds, e.g.
 	 * in a direct-access (dax) mapping, so let's just replicate the
-	 * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
+	 * !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
 	 */
 	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
 		if (vma->vm_flags & VM_MIXEDMAP) {
@@ -1933,7 +1929,8 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
 	 * without pte special, it would there be refcounted as a normal page.
 	 */
-	if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) &&
+	    !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
 		struct page *page;
 
 		/*
-- 
2.7.4

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Michal Hocko]

On Wed 11-04-18 10:03:36, Laurent Dufour wrote:
> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>  
>  	if (is_zero_pfn(pfn))
>  		return NULL;
> -check_pfn:
> +
> +check_pfn: __maybe_unused
>  	if (unlikely(pfn > highest_memmap_pfn)) {
>  		print_bad_pte(vma, addr, pte, NULL);
>  		return NULL;
> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>  	 * NOTE! We still have PageReserved() pages in the page tables.
>  	 * eg. VDSO mappings can cause them to exist.
>  	 */
> -out:
> +out: __maybe_unused
>  	return pfn_to_page(pfn);

Why do we need this ugliness all of the sudden?

-- 
Michal Hocko
SUSE Labs

Re: [PATCH v3 1/2] mm: introduce ARCH_HAS_PTE_SPECIAL

[Michal Hocko]

On Wed 11-04-18 10:03:35, Laurent Dufour wrote:
> Currently the PTE special supports is turned on in per architecture header
> files. Most of the time, it is defined in arch/*/include/asm/pgtable.h
> depending or not on some other per architecture static definition.
> 
> This patch introduce a new configuration variable to manage this directly
> in the Kconfig files. It would later replace __HAVE_ARCH_PTE_SPECIAL.
> 
> Here notes for some architecture where the definition of
> __HAVE_ARCH_PTE_SPECIAL is not obvious:
> 
> arm
>  __HAVE_ARCH_PTE_SPECIAL which is currently defined in
> arch/arm/include/asm/pgtable-3level.h which is included by
> arch/arm/include/asm/pgtable.h when CONFIG_ARM_LPAE is set.
> So select ARCH_HAS_PTE_SPECIAL if ARM_LPAE.
> 
> powerpc
> __HAVE_ARCH_PTE_SPECIAL is defined in 2 files:
>  - arch/powerpc/include/asm/book3s/64/pgtable.h
>  - arch/powerpc/include/asm/pte-common.h
> The first one is included if (PPC_BOOK3S & PPC64) while the second is
> included in all the other cases.
> So select ARCH_HAS_PTE_SPECIAL all the time.
> 
> sparc:
> __HAVE_ARCH_PTE_SPECIAL is defined if defined(__sparc__) &&
> defined(__arch64__) which are defined through the compiler in
> sparc/Makefile if !SPARC32 which I assume to be if SPARC64.
> So select ARCH_HAS_PTE_SPECIAL if SPARC64
> 
> There is no functional change introduced by this patch.
> 
> Suggested-by: Jerome Glisse <jglisse@redhat>
> Reviewed-by: Jerome Glisse <jglisse@redhat>
> Acked-by: David Rientjes <rientjes@google.com>
> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>

Looks good to me. I have checked x86 and the generic code and it looks
good to me. Anyway arch maintainers really have to double check this.
-- 
Michal Hocko
SUSE Labs

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Laurent Dufour]

On 11/04/2018 10:33, Michal Hocko wrote:
> On Wed 11-04-18 10:03:36, Laurent Dufour wrote:
>> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>>  
>>  	if (is_zero_pfn(pfn))
>>  		return NULL;
>> -check_pfn:
>> +
>> +check_pfn: __maybe_unused
>>  	if (unlikely(pfn > highest_memmap_pfn)) {
>>  		print_bad_pte(vma, addr, pte, NULL);
>>  		return NULL;
>> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>>  	 * NOTE! We still have PageReserved() pages in the page tables.
>>  	 * eg. VDSO mappings can cause them to exist.
>>  	 */
>> -out:
>> +out: __maybe_unused
>>  	return pfn_to_page(pfn);
> 
> Why do we need this ugliness all of the sudden?
Indeed the compiler doesn't complaint but in theory it should since these
labels are not used depending on CONFIG_ARCH_HAS_PTE_SPECIAL.

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Michal Hocko]

On Wed 11-04-18 10:41:23, Laurent Dufour wrote:
> On 11/04/2018 10:33, Michal Hocko wrote:
> > On Wed 11-04-18 10:03:36, Laurent Dufour wrote:
> >> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
> >>  
> >>  	if (is_zero_pfn(pfn))
> >>  		return NULL;
> >> -check_pfn:
> >> +
> >> +check_pfn: __maybe_unused
> >>  	if (unlikely(pfn > highest_memmap_pfn)) {
> >>  		print_bad_pte(vma, addr, pte, NULL);
> >>  		return NULL;
> >> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
> >>  	 * NOTE! We still have PageReserved() pages in the page tables.
> >>  	 * eg. VDSO mappings can cause them to exist.
> >>  	 */
> >> -out:
> >> +out: __maybe_unused
> >>  	return pfn_to_page(pfn);
> > 
> > Why do we need this ugliness all of the sudden?
> Indeed the compiler doesn't complaint but in theory it should since these
> labels are not used depending on CONFIG_ARCH_HAS_PTE_SPECIAL.

Well, such a warning would be quite pointless so I would rather not make
the code ugly. The value of unused label is quite questionable to start
with...

-- 
Michal Hocko
SUSE Labs

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Christophe LEROY]

Le 11/04/2018 à 10:03, Laurent Dufour a écrit :
> Remove the additional define HAVE_PTE_SPECIAL and rely directly on
> CONFIG_ARCH_HAS_PTE_SPECIAL.
> 
> There is no functional change introduced by this patch
> 
> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
> ---
>   mm/memory.c | 19 ++++++++-----------
>   1 file changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 96910c625daa..7f7dc7b2a341 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -817,17 +817,12 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
>    * PFNMAP mappings in order to support COWable mappings.
>    *
>    */
> -#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
> -# define HAVE_PTE_SPECIAL 1
> -#else
> -# define HAVE_PTE_SPECIAL 0
> -#endif
>   struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>   			     pte_t pte, bool with_public_device)
>   {
>   	unsigned long pfn = pte_pfn(pte);
>   
> -	if (HAVE_PTE_SPECIAL) {
> +	if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
>   		if (likely(!pte_special(pte)))
>   			goto check_pfn;
>   		if (vma->vm_ops && vma->vm_ops->find_special_page)
> @@ -862,7 +857,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>   		return NULL;
>   	}
>   
> -	/* !HAVE_PTE_SPECIAL case follows: */
> +	/* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
>   
>   	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
>   		if (vma->vm_flags & VM_MIXEDMAP) {
> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>   
>   	if (is_zero_pfn(pfn))
>   		return NULL;
> -check_pfn:
> +
> +check_pfn: __maybe_unused

See below

>   	if (unlikely(pfn > highest_memmap_pfn)) {
>   		print_bad_pte(vma, addr, pte, NULL);
>   		return NULL;
> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>   	 * NOTE! We still have PageReserved() pages in the page tables.
>   	 * eg. VDSO mappings can cause them to exist.
>   	 */
> -out:
> +out: __maybe_unused

Why do you need that change ?

There is no reason for the compiler to complain. It would complain if 
the goto was within a #ifdef, but all the purpose of using IS_ENABLED() 
is to allow the compiler to properly handle all possible cases. That's 
all the force of IS_ENABLED() compared to ifdefs, and that the reason 
why they are plebicited, ref Linux Codying style for a detailed explanation.

Christophe


>   	return pfn_to_page(pfn);
>   }
>   
> @@ -904,7 +900,7 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
>   	/*
>   	 * There is no pmd_special() but there may be special pmds, e.g.
>   	 * in a direct-access (dax) mapping, so let's just replicate the
> -	 * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
> +	 * !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
>   	 */
>   	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
>   		if (vma->vm_flags & VM_MIXEDMAP) {
> @@ -1933,7 +1929,8 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
>   	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
>   	 * without pte special, it would there be refcounted as a normal page.
>   	 */
> -	if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
> +	if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) &&
> +	    !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
>   		struct page *page;
>   
>   		/*
> 

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Christophe LEROY]

Le 11/04/2018 à 10:41, Laurent Dufour a écrit :
> On 11/04/2018 10:33, Michal Hocko wrote:
>> On Wed 11-04-18 10:03:36, Laurent Dufour wrote:
>>> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>>>   
>>>   	if (is_zero_pfn(pfn))
>>>   		return NULL;
>>> -check_pfn:
>>> +
>>> +check_pfn: __maybe_unused
>>>   	if (unlikely(pfn > highest_memmap_pfn)) {
>>>   		print_bad_pte(vma, addr, pte, NULL);
>>>   		return NULL;
>>> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>>>   	 * NOTE! We still have PageReserved() pages in the page tables.
>>>   	 * eg. VDSO mappings can cause them to exist.
>>>   	 */
>>> -out:
>>> +out: __maybe_unused
>>>   	return pfn_to_page(pfn);
>>
>> Why do we need this ugliness all of the sudden?
> Indeed the compiler doesn't complaint but in theory it should since these
> labels are not used depending on CONFIG_ARCH_HAS_PTE_SPECIAL.

Why should it complain ?

Regards
Christophe

> 

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Laurent Dufour]

On 11/04/2018 10:58, Christophe LEROY wrote:
> 
> 
> Le 11/04/2018 à 10:03, Laurent Dufour a écrit :
>> Remove the additional define HAVE_PTE_SPECIAL and rely directly on
>> CONFIG_ARCH_HAS_PTE_SPECIAL.
>>
>> There is no functional change introduced by this patch
>>
>> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
>> ---
>>   mm/memory.c | 19 ++++++++-----------
>>   1 file changed, 8 insertions(+), 11 deletions(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 96910c625daa..7f7dc7b2a341 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -817,17 +817,12 @@ static void print_bad_pte(struct vm_area_struct *vma,
>> unsigned long addr,
>>    * PFNMAP mappings in order to support COWable mappings.
>>    *
>>    */
>> -#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
>> -# define HAVE_PTE_SPECIAL 1
>> -#else
>> -# define HAVE_PTE_SPECIAL 0
>> -#endif
>>   struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>>                    pte_t pte, bool with_public_device)
>>   {
>>       unsigned long pfn = pte_pfn(pte);
>>   -    if (HAVE_PTE_SPECIAL) {
>> +    if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
>>           if (likely(!pte_special(pte)))
>>               goto check_pfn;
>>           if (vma->vm_ops && vma->vm_ops->find_special_page)
>> @@ -862,7 +857,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>> unsigned long addr,
>>           return NULL;
>>       }
>>   -    /* !HAVE_PTE_SPECIAL case follows: */
>> +    /* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
>>         if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
>>           if (vma->vm_flags & VM_MIXEDMAP) {
>> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>> unsigned long addr,
>>         if (is_zero_pfn(pfn))
>>           return NULL;
>> -check_pfn:
>> +
>> +check_pfn: __maybe_unused
> 
> See below
> 
>>       if (unlikely(pfn > highest_memmap_pfn)) {
>>           print_bad_pte(vma, addr, pte, NULL);
>>           return NULL;
>> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>> unsigned long addr,
>>        * NOTE! We still have PageReserved() pages in the page tables.
>>        * eg. VDSO mappings can cause them to exist.
>>        */
>> -out:
>> +out: __maybe_unused
> 
> Why do you need that change ?
> 
> There is no reason for the compiler to complain. It would complain if the goto
> was within a #ifdef, but all the purpose of using IS_ENABLED() is to allow the
> compiler to properly handle all possible cases. That's all the force of
> IS_ENABLED() compared to ifdefs, and that the reason why they are plebicited,
> ref Linux Codying style for a detailed explanation.

Fair enough.

Should I submit a v4 just to remove these so ugly __maybe_unused ?

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Christophe LEROY]

Le 11/04/2018 à 11:03, Laurent Dufour a écrit :
> 
> 
> On 11/04/2018 10:58, Christophe LEROY wrote:
>>
>>
>> Le 11/04/2018 à 10:03, Laurent Dufour a écrit :
>>> Remove the additional define HAVE_PTE_SPECIAL and rely directly on
>>> CONFIG_ARCH_HAS_PTE_SPECIAL.
>>>
>>> There is no functional change introduced by this patch
>>>
>>> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
>>> ---
>>>    mm/memory.c | 19 ++++++++-----------
>>>    1 file changed, 8 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/mm/memory.c b/mm/memory.c
>>> index 96910c625daa..7f7dc7b2a341 100644
>>> --- a/mm/memory.c
>>> +++ b/mm/memory.c
>>> @@ -817,17 +817,12 @@ static void print_bad_pte(struct vm_area_struct *vma,
>>> unsigned long addr,
>>>     * PFNMAP mappings in order to support COWable mappings.
>>>     *
>>>     */
>>> -#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
>>> -# define HAVE_PTE_SPECIAL 1
>>> -#else
>>> -# define HAVE_PTE_SPECIAL 0
>>> -#endif
>>>    struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
>>>                     pte_t pte, bool with_public_device)
>>>    {
>>>        unsigned long pfn = pte_pfn(pte);
>>>    -    if (HAVE_PTE_SPECIAL) {
>>> +    if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
>>>            if (likely(!pte_special(pte)))
>>>                goto check_pfn;
>>>            if (vma->vm_ops && vma->vm_ops->find_special_page)
>>> @@ -862,7 +857,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>>> unsigned long addr,
>>>            return NULL;
>>>        }
>>>    -    /* !HAVE_PTE_SPECIAL case follows: */
>>> +    /* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
>>>          if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
>>>            if (vma->vm_flags & VM_MIXEDMAP) {
>>> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>>> unsigned long addr,
>>>          if (is_zero_pfn(pfn))
>>>            return NULL;
>>> -check_pfn:
>>> +
>>> +check_pfn: __maybe_unused
>>
>> See below
>>
>>>        if (unlikely(pfn > highest_memmap_pfn)) {
>>>            print_bad_pte(vma, addr, pte, NULL);
>>>            return NULL;
>>> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>>> unsigned long addr,
>>>         * NOTE! We still have PageReserved() pages in the page tables.
>>>         * eg. VDSO mappings can cause them to exist.
>>>         */
>>> -out:
>>> +out: __maybe_unused
>>
>> Why do you need that change ?
>>
>> There is no reason for the compiler to complain. It would complain if the goto
>> was within a #ifdef, but all the purpose of using IS_ENABLED() is to allow the
>> compiler to properly handle all possible cases. That's all the force of
>> IS_ENABLED() compared to ifdefs, and that the reason why they are plebicited,
>> ref Linux Codying style for a detailed explanation.
> 
> Fair enough.
> 
> Should I submit a v4 just to remove these so ugly __maybe_unused ?
> 

Most likely, unless the mm maintainer agrees to remove them by himself 
when applying your patch ?

Christophe

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Laurent Dufour]

On 11/04/2018 11:09, Christophe LEROY wrote:
> 
> 
> Le 11/04/2018 à 11:03, Laurent Dufour a écrit :
>>
>>
>> On 11/04/2018 10:58, Christophe LEROY wrote:
>>>
>>>
>>> Le 11/04/2018 à 10:03, Laurent Dufour a écrit :
>>>> Remove the additional define HAVE_PTE_SPECIAL and rely directly on
>>>> CONFIG_ARCH_HAS_PTE_SPECIAL.
>>>>
>>>> There is no functional change introduced by this patch
>>>>
>>>> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
>>>> ---
>>>>    mm/memory.c | 19 ++++++++-----------
>>>>    1 file changed, 8 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/mm/memory.c b/mm/memory.c
>>>> index 96910c625daa..7f7dc7b2a341 100644
>>>> --- a/mm/memory.c
>>>> +++ b/mm/memory.c
>>>> @@ -817,17 +817,12 @@ static void print_bad_pte(struct vm_area_struct *vma,
>>>> unsigned long addr,
>>>>     * PFNMAP mappings in order to support COWable mappings.
>>>>     *
>>>>     */
>>>> -#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
>>>> -# define HAVE_PTE_SPECIAL 1
>>>> -#else
>>>> -# define HAVE_PTE_SPECIAL 0
>>>> -#endif
>>>>    struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long
>>>> addr,
>>>>                     pte_t pte, bool with_public_device)
>>>>    {
>>>>        unsigned long pfn = pte_pfn(pte);
>>>>    -    if (HAVE_PTE_SPECIAL) {
>>>> +    if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
>>>>            if (likely(!pte_special(pte)))
>>>>                goto check_pfn;
>>>>            if (vma->vm_ops && vma->vm_ops->find_special_page)
>>>> @@ -862,7 +857,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>>>> unsigned long addr,
>>>>            return NULL;
>>>>        }
>>>>    -    /* !HAVE_PTE_SPECIAL case follows: */
>>>> +    /* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
>>>>          if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
>>>>            if (vma->vm_flags & VM_MIXEDMAP) {
>>>> @@ -881,7 +876,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>>>> unsigned long addr,
>>>>          if (is_zero_pfn(pfn))
>>>>            return NULL;
>>>> -check_pfn:
>>>> +
>>>> +check_pfn: __maybe_unused
>>>
>>> See below
>>>
>>>>        if (unlikely(pfn > highest_memmap_pfn)) {
>>>>            print_bad_pte(vma, addr, pte, NULL);
>>>>            return NULL;
>>>> @@ -891,7 +887,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma,
>>>> unsigned long addr,
>>>>         * NOTE! We still have PageReserved() pages in the page tables.
>>>>         * eg. VDSO mappings can cause them to exist.
>>>>         */
>>>> -out:
>>>> +out: __maybe_unused
>>>
>>> Why do you need that change ?
>>>
>>> There is no reason for the compiler to complain. It would complain if the goto
>>> was within a #ifdef, but all the purpose of using IS_ENABLED() is to allow the
>>> compiler to properly handle all possible cases. That's all the force of
>>> IS_ENABLED() compared to ifdefs, and that the reason why they are plebicited,
>>> ref Linux Codying style for a detailed explanation.
>>
>> Fair enough.
>>
>> Should I submit a v4 just to remove these so ugly __maybe_unused ?
>>
> 
> Most likely, unless the mm maintainer agrees to remove them by himself when
> applying your patch ?

That was my point.

Andrew, should I send a v4 or could you wipe the 2 __maybe_unsued when applying
the patch ?

Thanks,
Laurent.

Re: [PATCH v3 2/2] mm: remove odd HAVE_PTE_SPECIAL

[Michal Hocko]

On Wed 11-04-18 12:32:07, Laurent Dufour wrote:
[...]
> Andrew, should I send a v4 or could you wipe the 2 __maybe_unsued when applying
> the patch ?

A follow $patch-fix should be better rather than post this again and
spam people with more emails.
-- 
Michal Hocko
SUSE Labs

[PATCH v4] mm: remove odd HAVE_PTE_SPECIAL

[Laurent Dufour]

Remove the additional define HAVE_PTE_SPECIAL and rely directly on
CONFIG_ARCH_HAS_PTE_SPECIAL.

There is no functional change introduced by this patch

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
 mm/memory.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 96910c625daa..345e562a138d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -817,17 +817,12 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
  * PFNMAP mappings in order to support COWable mappings.
  *
  */
-#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
-# define HAVE_PTE_SPECIAL 1
-#else
-# define HAVE_PTE_SPECIAL 0
-#endif
 struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 			     pte_t pte, bool with_public_device)
 {
 	unsigned long pfn = pte_pfn(pte);
 
-	if (HAVE_PTE_SPECIAL) {
+	if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
 		if (likely(!pte_special(pte)))
 			goto check_pfn;
 		if (vma->vm_ops && vma->vm_ops->find_special_page)
@@ -862,7 +857,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 		return NULL;
 	}
 
-	/* !HAVE_PTE_SPECIAL case follows: */
+	/* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
 
 	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
 		if (vma->vm_flags & VM_MIXEDMAP) {
@@ -881,6 +876,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 
 	if (is_zero_pfn(pfn))
 		return NULL;
+
 check_pfn:
 	if (unlikely(pfn > highest_memmap_pfn)) {
 		print_bad_pte(vma, addr, pte, NULL);
@@ -904,7 +900,7 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
 	/*
 	 * There is no pmd_special() but there may be special pmds, e.g.
 	 * in a direct-access (dax) mapping, so let's just replicate the
-	 * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
+	 * !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
 	 */
 	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
 		if (vma->vm_flags & VM_MIXEDMAP) {
@@ -1933,7 +1929,8 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
 	 * without pte special, it would there be refcounted as a normal page.
 	 */
-	if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) &&
+	    !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
 		struct page *page;
 
 		/*
-- 
2.7.4

Re: [PATCH v4] mm: remove odd HAVE_PTE_SPECIAL

[David Rientjes]

On Thu, 12 Apr 2018, Laurent Dufour wrote:

> Remove the additional define HAVE_PTE_SPECIAL and rely directly on
> CONFIG_ARCH_HAS_PTE_SPECIAL.
> 
> There is no functional change introduced by this patch
> 
> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>

Acked-by: David Rientjes <rientjes@google.com>