[PATCH 10/10] arch: fix has_transparent_hugepage()

Hugh Dickins
2016-04-05T21:02:54Z

I've just discovered that the useful-sounding has_transparent_hugepage()
is actually an architecture-dependent minefield: on some arches it only
builds if CONFIG_TRANSPARENT_HUGEPAGE=y, on others it's also there when
not, but on some of those (arm and arm64) it then gives the wrong answer;
and on mips alone it's marked __init, which would crash if called later
(but so far it has not been called later).

Straighten this out: make it available to all configs, with a sensible
default in asm-generic/pgtable.h, removing its definitions from those
arches (arc, arm, arm64, sparc, tile) which are served by the default,
adding #define has_transparent_hugepage has_transparent_hugepage to those
(mips, powerpc, s390, x86) which need to override the default at runtime,
and removing the __init from mips (but maybe that kind of code should be
avoided after init: set a static variable the first time it's called).

Signed-off-by: Hugh Dickins <hughd@google.com>
---
arch/arc/include/asm/hugepage.h | 2 -
arch/arm/include/asm/pgtable-3level.h | 5 ----
arch/arm64/include/asm/pgtable.h | 5 ----
arch/mips/include/asm/pgtable.h | 1
arch/mips/mm/tlb-r4k.c | 21 ++++++++---------
arch/powerpc/include/asm/book3s/64/pgtable.h | 1
arch/powerpc/include/asm/pgtable.h | 1
arch/s390/include/asm/pgtable.h | 1
arch/sparc/include/asm/pgtable_64.h | 2 -
arch/tile/include/asm/pgtable.h | 1
arch/x86/include/asm/pgtable.h | 1
include/asm-generic/pgtable.h | 8 ++++++
12 files changed, 23 insertions(+), 26 deletions(-)

--- a/arch/arc/include/asm/hugepage.h
+++ b/arch/arc/include/asm/hugepage.h
@@ -61,8 +61,6 @@ static inline void set_pmd_at(struct mm_
extern void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd);

-#define has_transparent_hugepage() 1
-
/* Generic variants assume pgtable_t is struct page *, hence need for these */
#define __HAVE_ARCH_PGTABLE_DEPOSIT
extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -281,11 +281,6 @@ static inline void set_pmd_at(struct mm_
flush_pmd_entry(pmdp);
}

-static inline int has_transparent_hugepage(void)
-{
- return 1;
-}
-
#endif /* __ASSEMBLY__ */

#endif /* _ASM_PGTABLE_3LEVEL_H */
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -304,11 +304,6 @@ static inline pgprot_t mk_sect_prot(pgpr

#define set_pmd_at(mm, addr, pmdp, pmd) set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))

-static inline int has_transparent_hugepage(void)
-{
- return 1;
-}
-
#define __pgprot_modify(prot,mask,bits) \
__pgprot((pgprot_val(prot) & ~(mask)) | (bits))

--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -468,6 +468,7 @@ static inline int io_remap_pfn_range(str

#ifdef CONFIG_TRANSPARENT_HUGEPAGE

+#define has_transparent_hugepage has_transparent_hugepage
extern int has_transparent_hugepage(void);

static inline int pmd_trans_huge(pmd_t pmd)
--- a/arch/mips/mm/tlb-r4k.c
+++ b/arch/mips/mm/tlb-r4k.c
@@ -399,19 +399,20 @@ void add_wired_entry(unsigned long entry

#ifdef CONFIG_TRANSPARENT_HUGEPAGE

-int __init has_transparent_hugepage(void)
+int has_transparent_hugepage(void)
{
- unsigned int mask;
- unsigned long flags;
+ static unsigned int mask = -1;

- local_irq_save(flags);
- write_c0_pagemask(PM_HUGE_MASK);
- back_to_back_c0_hazard();
- mask = read_c0_pagemask();
- write_c0_pagemask(PM_DEFAULT_MASK);
-
- local_irq_restore(flags);
+ if (mask == -1) { /* first call comes during __init */
+ unsigned long flags;

+ local_irq_save(flags);
+ write_c0_pagemask(PM_HUGE_MASK);
+ back_to_back_c0_hazard();
+ mask = read_c0_pagemask();
+ write_c0_pagemask(PM_DEFAULT_MASK);
+ local_irq_restore(flags);
+ }
return mask == PM_HUGE_MASK;
}

--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -219,6 +219,7 @@ extern void set_pmd_at(struct mm_struct
pmd_t *pmdp, pmd_t pmd);
extern void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd);
+#define has_transparent_hugepage has_transparent_hugepage
extern int has_transparent_hugepage(void);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -65,7 +65,6 @@ extern int gup_hugepte(pte_t *ptep, unsi
struct page **pages, int *nr);
#ifndef CONFIG_TRANSPARENT_HUGEPAGE
#define pmd_large(pmd) 0
-#define has_transparent_hugepage() 0
#endif
pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
bool *is_thp, unsigned *shift);
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1223,6 +1223,7 @@ static inline int pmd_trans_huge(pmd_t p
return pmd_val(pmd) & _SEGMENT_ENTRY_LARGE;
}

+#define has_transparent_hugepage has_transparent_hugepage
static inline int has_transparent_hugepage(void)
{
return MACHINE_HAS_HPAGE ? 1 : 0;
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -681,8 +681,6 @@ static inline unsigned long pmd_trans_hu
return pte_val(pte) & _PAGE_PMD_HUGE;
}

-#define has_transparent_hugepage() 1
-
static inline pmd_t pmd_mkold(pmd_t pmd)
{
pte_t pte = __pte(pmd_val(pmd));
--- a/arch/tile/include/asm/pgtable.h
+++ b/arch/tile/include/asm/pgtable.h
@@ -487,7 +487,6 @@ static inline pmd_t pmd_modify(pmd_t pmd
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-#define has_transparent_hugepage() 1
#define pmd_trans_huge pmd_huge_page
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -181,6 +181,7 @@ static inline int pmd_trans_huge(pmd_t p
return (pmd_val(pmd) & (_PAGE_PSE|_PAGE_DEVMAP)) == _PAGE_PSE;
}

+#define has_transparent_hugepage has_transparent_hugepage
static inline int has_transparent_hugepage(void)
{
return cpu_has_pse;
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -806,4 +806,12 @@ static inline int pmd_clear_huge(pmd_t *
#define io_remap_pfn_range remap_pfn_range
#endif

+#ifndef has_transparent_hugepage
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#define has_transparent_hugepage() 1
+#else
+#define has_transparent_hugepage() 0
+#endif
+#endif
+
#endif /* _ASM_GENERIC_PGTABLE_H */