Re: [PATCH 2/2] mm: hugetlbfs: Close race during teardown of hugetlbfs shared page tables
From: Michal Hocko <hidden>
Date: 2012-07-27 11:24:49
Also in:
lkml
Just a nit On Fri 27-07-12 11:46:05, Mel Gorman wrote:
quoted hunk ↗ jump to hunk
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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>