Re: [PATCH] mm/mprotect: fix compilation warning because of unused 'mm' varaible

[Song Liu <liu.song.a23@gmail.com>]

On Wed, May 8, 2019 at 4:50 AM Mike Rapoport <rppt@linux.ibm.com> wrote:
>
> Since commit 0cbe3e26abe0 ("mm: update ptep_modify_prot_start/commit to
> take vm_area_struct as arg") the only place that uses the local 'mm'
> variable in change_pte_range() is the call to set_pte_at().
>
> Many architectures define set_pte_at() as macro that does not use the 'mm'
> parameter, which generates the following compilation warning:
>
>  CC      mm/mprotect.o
> mm/mprotect.c: In function 'change_pte_range':
> mm/mprotect.c:42:20: warning: unused variable 'mm' [-Wunused-variable]
>   struct mm_struct *mm = vma->vm_mm;
>                     ^~
>
> Fix it by passing vma->mm to set_pte_at() and dropping the local 'mm'
> variable in change_pte_range().
>
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
>  mm/mprotect.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 028c724..61bfe24 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -39,7 +39,6 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
>                 unsigned long addr, unsigned long end, pgprot_t newprot,
>                 int dirty_accountable, int prot_numa)
>  {
> -       struct mm_struct *mm = vma->vm_mm;
>         pte_t *pte, oldpte;
>         spinlock_t *ptl;
>         unsigned long pages = 0;
> @@ -136,7 +135,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
>                                 newpte = swp_entry_to_pte(entry);
>                                 if (pte_swp_soft_dirty(oldpte))
>                                         newpte = pte_swp_mksoft_dirty(newpte);
> -                               set_pte_at(mm, addr, pte, newpte);
> +                               set_pte_at(vma->mm, addr, pte, newpte);

This should be vma->vm_mm.

Thanks,
Song

>
>                                 pages++;
>                         }
> --
> 2.7.4
>