From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
The below bug in fork lead to the rmap walk finding the parent huge-pmd twice
instead of just one, because the anon_vma_chain objects of the child vma still
point to the vma->vm_mm of the parent. The below patch fixes it by making the
rmap walk accurate during fork. It's not a big deal normally but it
worth being accurate considering the cost is the same.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
diff --git a/kernel/fork.c b/kernel/fork.c
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -360,10 +360,10 @@ static int dup_mmap(struct mm_struct *mm
if (IS_ERR(pol))
goto fail_nomem_policy;
vma_set_policy(tmp, pol);
+ tmp->vm_mm = mm;
if (anon_vma_fork(tmp, mpnt))
goto fail_nomem_anon_vma_fork;
tmp->vm_flags &= ~VM_LOCKED;
- tmp->vm_mm = mm;
tmp->vm_next = tmp->vm_prev = NULL;
file = tmp->vm_file;
if (file) {
--
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