rmap: add anon_vma bug checks
Verify the refcounting doesn't go wrong, and resurrect the check in
__page_check_anon_rmap as in old anon-vma code.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/rmap.c b/mm/rmap.c
index 2f855ba..4d152a6 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -811,6 +811,7 @@
* are initially only visible via the pagetables, and the pte is locked
* over the call to page_add_new_anon_rmap.
*/
+ BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
BUG_ON(page->index != linear_page_index(vma, address));
#endif
}
@@ -1408,6 +1409,7 @@
*/
void drop_anon_vma(struct anon_vma *anon_vma)
{
+ BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0);
if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
struct anon_vma *root = anon_vma->root;
int empty = list_empty(&anon_vma->head);
@@ -1419,6 +1421,7 @@
* the refcount on the root and check if we need to free it.
*/
if (empty && anon_vma != root) {
+ BUG_ON(atomic_read(&root->external_refcount) <= 0);
last_root_user = atomic_dec_and_test(&root->external_refcount);
root_empty = list_empty(&root->head);
}