On Tue, Dec 11, 2018 at 01:12:54PM -0800, David Rientjes wrote:
> On Tue, 11 Dec 2018, Jerome Glisse wrote:
>
> > On Tue, Dec 11, 2018 at 09:04:43PM +0100, Arnd Bergmann wrote:
> > > The macro version of mmu_notifier_range_init() for CONFIG_MMU_NOTIFIER=n
> > > does not evaluate all its arguments, leading to a warning in one case:
> > >
> > > mm/migrate.c: In function 'migrate_vma_pages':
> > > mm/migrate.c:2711:20: error: unused variable 'mm'
> > > [-Werror=unused-variable]
> > > struct mm_struct *mm = vma->vm_mm;
> > >
> > > Pass down the 'mm' as into the inline function as well so gcc can
> > > see why the variable exists.
> > >
> > > Fixes: 137d92bd73b1 ("mm/mmu_notifier: use structure for
> > > invalidate_range_start/end calls v2")
> >
> > What about changing migrate.c (i actualy tried to do that everywhere in
> > the patchset but i missed that spot) So we avoid one useless variable on
> > such configuration:
> >
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index f02bb4b22c1a..883fce631f47 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -2701,7 +2701,6 @@ static void migrate_vma_pages(struct migrate_vma
> > *migrate)
> > const unsigned long npages = migrate->npages;
> > const unsigned long start = migrate->start;
> > struct vm_area_struct *vma = migrate->vma;
> > - struct mm_struct *mm = vma->vm_mm;
> > struct mmu_notifier_range range;
> > unsigned long addr, i;
> > bool notified = false;
> > @@ -2724,8 +2723,8 @@ static void migrate_vma_pages(struct migrate_vma
> > *migrate)
> > if (!notified) {
> > notified = true;
> >
> > - mmu_notifier_range_init(&range, mm, addr,
> > - migrate->end,
> > + mmu_notifier_range_init(&range, vma->vm_mm,
> > + addr, migrate->end,
> > MMU_NOTIFY_CLEAR);
> > mmu_notifier_invalidate_range_start(&range);
> > }
>
> Wouldn't it be better to just declare mmu_notifier_range_init() as a
> static inline function rather than a #define to avoid this warning?
The define trick is use to drop the event parameter so that we do not
need to define the event value for CONFIG_MMU_NOTIFIER=n case.
Cheers,
Jérôme
