Messages in this thread | | | Date | Fri, 27 Jul 2012 13:24:45 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH 2/2] mm: hugetlbfs: Close race during teardown of hugetlbfs shared page tables |
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Just a nit
On Fri 27-07-12 11:46:05, Mel Gorman wrote: > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index fd1d530..8c6e5a5 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2429,6 +2429,25 @@ again: > tlb_end_vma(tlb, vma); > } >
I would welcome a comment here. Something like: /* * Called when the VMA is on the way out and page tables will be freed * by free_pagetables. * i_mmap_mutex has to be held when calling this function */
> +void __unmap_hugepage_range_final(struct mmu_gather *tlb, > + struct vm_area_struct *vma, unsigned long start, > + unsigned long end, struct page *ref_page) > +{ > + __unmap_hugepage_range(tlb, vma, start, end, ref_page); > + > + /* > + * Clear this flag so that x86's huge_pmd_share page_table_shareable > + * test will fail on a vma being torn down, and not grab a page table > + * on its way out. We're lucky that the flag has such an appropriate > + * name, and can in fact be safely cleared here. We could clear it > + * before the __unmap_hugepage_range above, but all that's necessary > + * is to clear it before releasing the i_mmap_mutex. This works > + * because in the context this is called, the VMA is about to be > + * destroyed and the i_mmap_mutex is held. > + */ > + vma->vm_flags &= ~VM_MAYSHARE; > +} > +
-- Michal Hocko SUSE Labs
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