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thp: add pmd mangling functions to x86
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Add needed pmd mangling functions with symmetry with their pte
counterparts.  pmdp_splitting_flush() is the only new addition on the pmd_
methods and it's needed to serialize the VM against split_huge_page.  It
simply atomically sets the splitting bit in a similar way
pmdp_clear_flush_young atomically clears the accessed bit.
pmdp_splitting_flush() also has to flush the tlb to make it effective
against gup_fast, but it wouldn't really require to flush the tlb too.
Just the tlb flush is the simplest operation we can invoke to serialize
pmdp_splitting_flush() against gup_fast.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Andrea Arcangeli authored and Linus Torvalds committed Jan 14, 2011
1 parent e2cda32 commit db3eb96
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Showing 3 changed files with 179 additions and 8 deletions.
2 changes: 1 addition & 1 deletion arch/x86/include/asm/pgtable.h
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Original file line number Diff line number Diff line change
Expand Up @@ -353,7 +353,7 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
* Currently stuck as a macro due to indirect forward reference to
* linux/mmzone.h's __section_mem_map_addr() definition:
*/
#define pmd_page(pmd) pfn_to_page(pmd_val(pmd) >> PAGE_SHIFT)
#define pmd_page(pmd) pfn_to_page((pmd_val(pmd) & PTE_PFN_MASK) >> PAGE_SHIFT)

/*
* the pmd page can be thought of an array like this: pmd_t[PTRS_PER_PMD]
Expand Down
119 changes: 112 additions & 7 deletions arch/x86/include/asm/pgtable_64.h
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,16 @@ static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
native_set_pte(ptep, pte);
}

static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
{
*pmdp = pmd;
}

static inline void native_pmd_clear(pmd_t *pmd)
{
native_set_pmd(pmd, native_make_pmd(0));
}

static inline pte_t native_ptep_get_and_clear(pte_t *xp)
{
#ifdef CONFIG_SMP
Expand All @@ -72,14 +82,17 @@ static inline pte_t native_ptep_get_and_clear(pte_t *xp)
#endif
}

static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
{
*pmdp = pmd;
}

static inline void native_pmd_clear(pmd_t *pmd)
static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
{
native_set_pmd(pmd, native_make_pmd(0));
#ifdef CONFIG_SMP
return native_make_pmd(xchg(&xp->pmd, 0));
#else
/* native_local_pmdp_get_and_clear,
but duplicated because of cyclic dependency */
pmd_t ret = *xp;
native_pmd_clear(xp);
return ret;
#endif
}

static inline void native_set_pud(pud_t *pudp, pud_t pud)
Expand Down Expand Up @@ -181,6 +194,98 @@ static inline int pmd_trans_huge(pmd_t pmd)
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

#define mk_pmd(page, pgprot) pfn_pmd(page_to_pfn(page), (pgprot))

#define __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
extern int pmdp_set_access_flags(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp,
pmd_t entry, int dirty);

#define __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
extern int pmdp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp);

#define __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);


#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
extern void pmdp_splitting_flush(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp);

#define __HAVE_ARCH_PMD_WRITE
static inline int pmd_write(pmd_t pmd)
{
return pmd_flags(pmd) & _PAGE_RW;
}

#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp)
{
pmd_t pmd = native_pmdp_get_and_clear(pmdp);
pmd_update(mm, addr, pmdp);
return pmd;
}

#define __HAVE_ARCH_PMDP_SET_WRPROTECT
static inline void pmdp_set_wrprotect(struct mm_struct *mm,
unsigned long addr, pmd_t *pmdp)
{
clear_bit(_PAGE_BIT_RW, (unsigned long *)&pmdp->pmd);
pmd_update(mm, addr, pmdp);
}

static inline int pmd_young(pmd_t pmd)
{
return pmd_flags(pmd) & _PAGE_ACCESSED;
}

static inline pmd_t pmd_set_flags(pmd_t pmd, pmdval_t set)
{
pmdval_t v = native_pmd_val(pmd);

return native_make_pmd(v | set);
}

static inline pmd_t pmd_clear_flags(pmd_t pmd, pmdval_t clear)
{
pmdval_t v = native_pmd_val(pmd);

return native_make_pmd(v & ~clear);
}

static inline pmd_t pmd_mkold(pmd_t pmd)
{
return pmd_clear_flags(pmd, _PAGE_ACCESSED);
}

static inline pmd_t pmd_wrprotect(pmd_t pmd)
{
return pmd_clear_flags(pmd, _PAGE_RW);
}

static inline pmd_t pmd_mkdirty(pmd_t pmd)
{
return pmd_set_flags(pmd, _PAGE_DIRTY);
}

static inline pmd_t pmd_mkhuge(pmd_t pmd)
{
return pmd_set_flags(pmd, _PAGE_PSE);
}

static inline pmd_t pmd_mkyoung(pmd_t pmd)
{
return pmd_set_flags(pmd, _PAGE_ACCESSED);
}

static inline pmd_t pmd_mkwrite(pmd_t pmd)
{
return pmd_set_flags(pmd, _PAGE_RW);
}

#endif /* !__ASSEMBLY__ */

#endif /* _ASM_X86_PGTABLE_64_H */
66 changes: 66 additions & 0 deletions arch/x86/mm/pgtable.c
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Original file line number Diff line number Diff line change
Expand Up @@ -320,6 +320,25 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
return changed;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_set_access_flags(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp,
pmd_t entry, int dirty)
{
int changed = !pmd_same(*pmdp, entry);

VM_BUG_ON(address & ~HPAGE_PMD_MASK);

if (changed && dirty) {
*pmdp = entry;
pmd_update_defer(vma->vm_mm, address, pmdp);
flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
}

return changed;
}
#endif

int ptep_test_and_clear_young(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
{
Expand All @@ -335,6 +354,23 @@ int ptep_test_and_clear_young(struct vm_area_struct *vma,
return ret;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp)
{
int ret = 0;

if (pmd_young(*pmdp))
ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
(unsigned long *) &pmdp->pmd);

if (ret)
pmd_update(vma->vm_mm, addr, pmdp);

return ret;
}
#endif

int ptep_clear_flush_young(struct vm_area_struct *vma,
unsigned long address, pte_t *ptep)
{
Expand All @@ -347,6 +383,36 @@ int ptep_clear_flush_young(struct vm_area_struct *vma,
return young;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_clear_flush_young(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp)
{
int young;

VM_BUG_ON(address & ~HPAGE_PMD_MASK);

young = pmdp_test_and_clear_young(vma, address, pmdp);
if (young)
flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

return young;
}

void pmdp_splitting_flush(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp)
{
int set;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
set = !test_and_set_bit(_PAGE_BIT_SPLITTING,
(unsigned long *)&pmdp->pmd);
if (set) {
pmd_update(vma->vm_mm, address, pmdp);
/* need tlb flush only to serialize against gup-fast */
flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
}
}
#endif

/**
* reserve_top_address - reserves a hole in the top of kernel address space
* @reserve - size of hole to reserve
Expand Down

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