On Sun, 25 Mar 2007, David Rientjes wrote:
> Add ptep_test_and_clear_{dirty,young} to i386. They advertise that they
> have it and there is at least one place where it needs to be called
> without the page table lock: to clear the accessed bit on write to
Without the page table lock??
> /proc/pid/clear_refs.
>
> ptep_clear_flush_{dirty,young} are updated to use the new functions. The
> overall net effect to current users of ptep_clear_flush_{dirty,young} is
> that we introduce an additional branch.
We need to Cc Zach on this: git blame indicates it was he who replaced
i386's ptep_test_and_clear_{dirty,young} by that "We don't actually
have these" comment - it looks a bit as if what you want to do might
violate the assumptions he wants to make, but I don't grasp it.
Hugh
>
> Cc: Hugh Dickins <[EMAIL PROTECTED]>
> Cc: Ingo Molnar <[EMAIL PROTECTED]>
> Signed-off-by: David Rientjes <[EMAIL PROTECTED]>
> ---
> include/asm-i386/pgtable.h | 25 +++++++++++++++++--------
> 1 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h
> --- a/include/asm-i386/pgtable.h
> +++ b/include/asm-i386/pgtable.h
> @@ -283,12 +283,23 @@ do {
> \
> } \
> } while (0)
>
> -/*
> - * We don't actually have these, but we want to advertise them so that
> - * we can encompass the flush here.
> - */
> #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY
> +static inline int ptep_test_and_clear_dirty(struct vm_area_struct *vma,
> + unsigned long addr, pte_t *ptep)
> +{
> + if (!pte_dirty(*ptep))
> + return 0;
> + return test_and_clear_bit(_PAGE_BIT_DIRTY, &ptep->pte_low);
> +}
> +
> #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
> +static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
> + unsigned long addr, pte_t *ptep)
> +{
> + if (!pte_young(*ptep))
> + return 0;
> + return test_and_clear_bit(_PAGE_BIT_ACCESSED, &ptep->pte_low);
> +}
>
> /*
> * Rules for using ptep_establish: the pte MUST be a user pte, and
> @@ -305,9 +316,8 @@ do {
> \
> #define ptep_clear_flush_dirty(vma, address, ptep) \
> ({ \
> int __dirty; \
> - __dirty = pte_dirty(*(ptep)); \
> + __dirty = ptep_test_and_clear_dirty((vma), (address), (ptep)); \
> if (__dirty) { \
> - clear_bit(_PAGE_BIT_DIRTY, &(ptep)->pte_low); \
> pte_update_defer((vma)->vm_mm, (address), (ptep)); \
> flush_tlb_page(vma, address); \
> } \
> @@ -318,9 +328,8 @@ do {
> \
> #define ptep_clear_flush_young(vma, address, ptep) \
> ({ \
> int __young; \
> - __young = pte_young(*(ptep)); \
> + __young = ptep_test_and_clear_young((vma), (address), (ptep)); \
> if (__young) { \
> - clear_bit(_PAGE_BIT_ACCESSED, &(ptep)->pte_low); \
> pte_update_defer((vma)->vm_mm, (address), (ptep)); \
> flush_tlb_page(vma, address); \
> } \
-
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