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    Subject[PATCH v9 14/24] mm: Introduce __maybe_mkwrite()
    Date
    The current maybe_mkwrite() is getting passed the pointer to the vma
    structure to fetch the vm_flags field.

    When dealing with the speculative page fault handler, it will be better to
    rely on the cached vm_flags value stored in the vm_fault structure.

    This patch introduce a __maybe_mkwrite() service which can be called by
    passing the value of the vm_flags field.

    There is no change functional changes expected for the other callers of
    maybe_mkwrite().

    Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
    ---
    include/linux/mm.h | 9 +++++++--
    mm/memory.c | 6 +++---
    2 files changed, 10 insertions(+), 5 deletions(-)

    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index dfa81a638b7c..a84ddc218bbd 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -684,13 +684,18 @@ void free_compound_page(struct page *page);
    * pte_mkwrite. But get_user_pages can cause write faults for mappings
    * that do not have writing enabled, when used by access_process_vm.
    */
    -static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
    +static inline pte_t __maybe_mkwrite(pte_t pte, unsigned long vma_flags)
    {
    - if (likely(vma->vm_flags & VM_WRITE))
    + if (likely(vma_flags & VM_WRITE))
    pte = pte_mkwrite(pte);
    return pte;
    }

    +static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
    +{
    + return __maybe_mkwrite(pte, vma->vm_flags);
    +}
    +
    int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
    struct page *page);
    int finish_fault(struct vm_fault *vmf);
    diff --git a/mm/memory.c b/mm/memory.c
    index 0a0a483d9a65..af0338fbc34d 100644
    --- a/mm/memory.c
    +++ b/mm/memory.c
    @@ -2472,7 +2472,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)

    flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
    entry = pte_mkyoung(vmf->orig_pte);
    - entry = maybe_mkwrite(pte_mkdirty(entry), vma);
    + entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
    if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
    update_mmu_cache(vma, vmf->address, vmf->pte);
    pte_unmap_unlock(vmf->pte, vmf->ptl);
    @@ -2549,8 +2549,8 @@ static int wp_page_copy(struct vm_fault *vmf)
    inc_mm_counter_fast(mm, MM_ANONPAGES);
    }
    flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
    - entry = mk_pte(new_page, vma->vm_page_prot);
    - entry = maybe_mkwrite(pte_mkdirty(entry), vma);
    + entry = mk_pte(new_page, vmf->vma_page_prot);
    + entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
    /*
    * Clear the pte entry and flush it first, before updating the
    * pte with the new entry. This will avoid a race condition
    --
    2.7.4
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