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Commit 44ab57a0 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds
Browse files

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: default avatarAndrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 21d0d443

mm/rmap.c

+3 −0
Original line number Original line Diff line number Diff line
@@ -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);

		}

		}