Talking to Robin and Jack we found taht we still have a hole during fork.
Fork may set a pte writeprotect. At that point the remote pte are
not marked readonly(!). Remote writes may occur to pages that are marked
readonly locally without this patch.
mmu_notifier: Provide invalidate_range on fork
On fork we change ptes in cow mappings to readonly. This means we must
invalidate the ptes so that they are reestablished later with proper
permission.
Signed-off-by: Christoph Lameter <[EMAIL PROTECTED]>
---
mm/memory.c | 6 ++++++
1 file changed, 6 insertions(+)
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c 2008-01-31 13:42:35.000000000 -0800
+++ linux-2.6/mm/memory.c 2008-01-31 13:47:31.000000000 -0800
@@ -602,6 +602,9 @@ int copy_page_range(struct mm_struct *ds
if (is_vm_hugetlb_page(vma))
return copy_hugetlb_page_range(dst_mm, src_mm, vma);
+ if (is_cow_mapping(vma->vm_flags))
+ mmu_notifier(invalidate_range_begin, src_mm, addr, end, 0);
+
dst_pgd = pgd_offset(dst_mm, addr);
src_pgd = pgd_offset(src_mm, addr);
do {
@@ -612,6 +615,9 @@ int copy_page_range(struct mm_struct *ds
vma, addr, next))
return -ENOMEM;
} while (dst_pgd++, src_pgd++, addr = next, addr != end);
+
+ if (is_cow_mapping(vma->vm_flags))
+ mmu_notifier(invalidate_range_end, src_mm, 0);
return 0;
}
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