On 10/30/22 11:52, Nadav Amit wrote:
> On Oct 30, 2022, at 11:43 AM, Peter Xu <peterx@xxxxxxxxxx> wrote:
>
> > The loop comes from 7e027b14d53e ("vm: simplify unmap_vmas() calling
> > convention", 2012-05-06), where zap_page_range() was used to replace a call
> > to unmap_vmas() because the patch wanted to eliminate the zap details
> > pointer for unmap_vmas(), which makes sense.
> >
> > I didn't check the old code, but from what I can tell (and also as Mike
> > pointed out) I don't think zap_page_range() in the lastest code base is
> > ever used on multi-vma at all. Otherwise the mmu notifier is already
> > broken - see mmu_notifier_range_init() where the vma pointer is also part
> > of the notification.
> >
> > Perhaps we should just remove the loop?
>
> There is already zap_page_range_single() that does exactly that. Just need
> to export it.
I was thinking that zap_page_range() should perform a notification call for
each vma within the loop. Something like this?
@@ -1704,15 +1704,21 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
MA_STATE(mas, mt, vma->vm_end, vma->vm_end);
lru_add_drain();
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
- start, start + size);
tlb_gather_mmu(&tlb, vma->vm_mm);
update_hiwater_rss(vma->vm_mm);
- mmu_notifier_invalidate_range_start(&range);
do {
- unmap_single_vma(&tlb, vma, start, range.end, NULL);
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma,
+ vma->vm_mm,
+ max(start, vma->vm_start),
+ min(start + size, vma->vm_end));
+ if (is_vm_hugetlb_page(vma))
+ adjust_range_if_pmd_sharing_possible(vma,
+ &range.start,
+ &range.end);
+ mmu_notifier_invalidate_range_start(&range);
+ unmap_single_vma(&tlb, vma, start, start + size, NULL);
+ mmu_notifier_invalidate_range_end(&range);
} while ((vma = mas_find(&mas, end - 1)) != NULL);
- mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}
One thing to keep in mind is that this patch is a fix that must be
backported to stable. Therefore, I do not think we want to add too
many changes out of the direct scope of the fix.
We can always change things like this in follow up patches.
--
Mike Kravetz
