Always passing mm and vma down (was: [RFC][PATCH] Convert do_no_page() to a hook to avoid DFS race)

Ingo Oeser
2003-05-31T16:11:27Z

Hi there,

On Fri, May 30, 2003 at 04:41:50PM -0700, Paul E. McKenney wrote:
> -struct page *
> -ia32_install_shared_page (struct vm_area_struct *vma, unsigned long address, int no_share)
> +int
> +ia32_install_shared_page (struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access, pmd_t *pmd)
> {
> struct page *pg = ia32_shared_page[(address - vma->vm_start)/PAGE_SIZE];
>
> get_page(pg);
> - return pg;
> + return install_new_page(mm, vma, address, write_access, pmd, pg);
> }

Why do we always pass mm and vma down, even if vma->vm_mm
contains the mm, where the vma belongs to? Is the connection
between a vma and its mm also protected by the mmap_sem?

Is this really necessary or an oversight and we waste a lot of
stack in a lot of places?

If we just need it for accounting: We need current->mm, if we
need it to locate the next vma relatively to this vma, vma->vm_mm
is the one.

Puzzled

Ingo Oeser