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authorJan Schmidt <list.btrfs@jan-o-sch.net>2012-05-22 16:56:50 +0400
committerJan Schmidt <list.btrfs@jan-o-sch.net>2012-05-26 14:17:49 +0400
commitcd1b413c5c863a96bfdeab8e91b1fb3a52665e42 (patch)
treea433c13c530c487f2d7e209402ef72ec67e48647 /fs/btrfs/ulist.c
parentb9fab919b748c7b39c19ff236ed6c5682c266dde (diff)
downloadlinux-cd1b413c5c863a96bfdeab8e91b1fb3a52665e42.tar.xz
Btrfs: ulist realloc bugfix
ulist_next gets the pointer to the previously returned element to find the next element from there. However, when we call ulist_add while iteration with ulist_next is in progress (ulist explicitly supports this), we can realloc the ulist internal memory, which makes the pointer to the previous element useless. Instead, we now use an iterator parameter that's independent from the internal pointers. Reported-by: Alexander Block <ablock84@googlemail.com> Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Diffstat (limited to 'fs/btrfs/ulist.c')
-rw-r--r--fs/btrfs/ulist.c23
1 files changed, 8 insertions, 15 deletions
diff --git a/fs/btrfs/ulist.c b/fs/btrfs/ulist.c
index 12f5147bd2b1..17e68bdc307c 100644
--- a/fs/btrfs/ulist.c
+++ b/fs/btrfs/ulist.c
@@ -23,9 +23,9 @@
*
* ulist = ulist_alloc();
* ulist_add(ulist, root);
- * elem = NULL;
+ * ULIST_ITER_INIT(&uiter);
*
- * while ((elem = ulist_next(ulist, elem)) {
+ * while ((elem = ulist_next(ulist, &uiter)) {
* for (all child nodes n in elem)
* ulist_add(ulist, n);
* do something useful with the node;
@@ -188,33 +188,26 @@ EXPORT_SYMBOL(ulist_add);
/**
* ulist_next - iterate ulist
* @ulist: ulist to iterate
- * @prev: previously returned element or %NULL to start iteration
+ * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
*
* Note: locking must be provided by the caller. In case of rwlocks only read
* locking is needed
*
- * This function is used to iterate an ulist. The iteration is started with
- * @prev = %NULL. It returns the next element from the ulist or %NULL when the
+ * This function is used to iterate an ulist.
+ * It returns the next element from the ulist or %NULL when the
* end is reached. No guarantee is made with respect to the order in which
* the elements are returned. They might neither be returned in order of
* addition nor in ascending order.
* It is allowed to call ulist_add during an enumeration. Newly added items
* are guaranteed to show up in the running enumeration.
*/
-struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_node *prev)
+struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
{
- int next;
-
if (ulist->nnodes == 0)
return NULL;
-
- if (!prev)
- return &ulist->nodes[0];
-
- next = (prev - ulist->nodes) + 1;
- if (next < 0 || next >= ulist->nnodes)
+ if (uiter->i < 0 || uiter->i >= ulist->nnodes)
return NULL;
- return &ulist->nodes[next];
+ return &ulist->nodes[uiter->i++];
}
EXPORT_SYMBOL(ulist_next);