On Sat, 10 Dec 2011 13:35:39 +0100
Carsten Otte <[email protected]> wrote:
> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -393,6 +393,33 @@ out_unmap:
> }
> EXPORT_SYMBOL_GPL(gmap_map_segment);
>
> +static pmd_t *__pmdp_for_addr(struct mm_struct *mm, unsigned long addr)
> +{
> + struct vm_area_struct *vma;
> + pgd_t *pgd;
> + pud_t *pud;
> + pmd_t *pmd;
> +
> + vma = find_vma(mm, addr);
> + if (!vma || (vma->vm_start > addr))
> + return ERR_PTR(-EFAULT);
> +
> + pgd = pgd_offset(mm, addr);
> + pud = pud_alloc(mm, pgd, addr);
> + if (!pud)
> + return ERR_PTR(-ENOMEM);
> +
> + pmd = pmd_alloc(mm, pud, addr);
> + if (!pmd)
> + return ERR_PTR(-ENOMEM);
> +
> + if (!pmd_present(*pmd) &&
> + __pte_alloc(mm, vma, pmd, addr))
> + return ERR_PTR(-ENOMEM);
> +
> + return pmd;
> +}
> +
> /*
> * this function is assumed to be called with mmap_sem held
> */
The __pmdp_for_addr function is fine for the usage in __gmap_fault.
> @@ -806,6 +820,26 @@ int s390_enable_sie(void)
> }
> EXPORT_SYMBOL_GPL(s390_enable_sie);
>
> +pte_t *ptep_for_addr(unsigned long addr)
> +{
> + pmd_t *pmd;
> + pte_t *pte;
> +
> + down_read(¤t->mm->mmap_sem);
> +
> + pmd = __pmdp_for_addr(current->mm, addr);
> + if (IS_ERR(pmd)) {
> + pte = (pte_t *)pmd;
> + goto up_out;
> + }
> +
> + pte = pte_offset(pmd, addr);
> +up_out:
> + up_read(¤t->mm->mmap_sem);
> + return pte;
> +}
> +EXPORT_SYMBOL_GPL(ptep_for_addr);
> +
> #if defined(CONFIG_DEBUG_PAGEALLOC) && defined(CONFIG_HIBERNATION)
> bool kernel_page_present(struct page *page)
> {
There is a fundamental locking sanfu. The pointer the the page table
entry is only valid until the mmap_sem is released. The down_read/up_read
has to be done in the caller.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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