Commit a247c3a9 authored Sep 22, 2010 by Andrea Arcangeli Committed by Linus Torvalds Sep 22, 2010

rmap: fix walk during fork



The below bug in fork led to the rmap walk finding the parent huge-pmd
twice instead of just once, because the anon_vma_chain objects of the
child vma still point to the vma->vm_mm of the parent.

The 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@redhat.com>
Acked-by: Johannes Weiner <jweiner@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent df08cdc7

kernel/fork.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -356,10 +356,10 @@ static int dup_mmap(struct mm_struct mm, struct mm_struct oldmm)
	if (IS_ERR(pol))		if (IS_ERR(pol))
	goto fail_nomem_policy;		goto fail_nomem_policy;
	vma_set_policy(tmp, pol);		vma_set_policy(tmp, pol);
			tmp->vm_mm = mm;
	if (anon_vma_fork(tmp, mpnt))		if (anon_vma_fork(tmp, mpnt))
	goto fail_nomem_anon_vma_fork;		goto fail_nomem_anon_vma_fork;
	tmp->vm_flags &= ~VM_LOCKED;		tmp->vm_flags &= ~VM_LOCKED;
	tmp->vm_mm = mm;
	tmp->vm_next = tmp->vm_prev = NULL;		tmp->vm_next = tmp->vm_prev = NULL;
	file = tmp->vm_file;		file = tmp->vm_file;
	if (file) {		if (file) {