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rmap: add anon_vma bug checks

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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>
This commit is contained in:
Andrea Arcangeli 2010-08-09 17:19:10 -07:00 • committed by Linus Torvalds
parent 21d0d443cd
commit 44ab57a06d
1 changed files with 3 additions and 0 deletions
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3
mm/rmap.c
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@ -811,6 +811,7 @@ static void __page_check_anon_rmap(struct page *page,
* are initially only visible via the pagetables, and the pte is locked * are initially only visible via the pagetables, and the pte is locked
* over the call to page_add_new_anon_rmap. * 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)); BUG_ON(page->index != linear_page_index(vma, address));
#endif #endif
} }
@ -1408,6 +1409,7 @@ int try_to_munlock(struct page *page)
*/ */
void drop_anon_vma(struct anon_vma *anon_vma) 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)) { if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
struct anon_vma *root = anon_vma->root; struct anon_vma *root = anon_vma->root;
int empty = list_empty(&anon_vma->head); int empty = list_empty(&anon_vma->head);
@ -1419,6 +1421,7 @@ void drop_anon_vma(struct anon_vma *anon_vma)
* the refcount on the root and check if we need to free it. * the refcount on the root and check if we need to free it.
*/ */
if (empty && anon_vma != root) { if (empty && anon_vma != root) {
BUG_ON(atomic_read(&root->external_refcount) <= 0);
last_root_user = atomic_dec_and_test(&root->external_refcount); last_root_user = atomic_dec_and_test(&root->external_refcount);
root_empty = list_empty(&root->head); root_empty = list_empty(&root->head);
} }