Commit e27c5b9d authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe

writeback: remove broken rbtree_postorder_for_each_entry_safe() usage in cgwb_bdi_destroy()

a20135ff ("writeback: don't drain bdi_writeback_congested on bdi
destruction") added rbtree_postorder_for_each_entry_safe() which is
used to remove all entries; however, according to Cody, the iterator
isn't safe against operations which may rebalance the tree.  Fix it by
switching to repeatedly removing rb_first() until empty.
Signed-off-by: default avatarTejun Heo <>
Reported-by: default avatarCody P Schafer <>
Fixes: a20135ff ("writeback: don't drain bdi_writeback_congested on bdi destruction")
Link: default avatarJens Axboe <>
parent 0dfc70c3
......@@ -681,7 +681,7 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
struct radix_tree_iter iter;
struct bdi_writeback_congested *congested, *congested_n;
struct rb_node *rbn;
void **slot;
WARN_ON(test_bit(WB_registered, &bdi->wb.state));
......@@ -691,9 +691,11 @@ static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
rbtree_postorder_for_each_entry_safe(congested, congested_n,
&bdi->cgwb_congested_tree, rb_node) {
rb_erase(&congested->rb_node, &bdi->cgwb_congested_tree);
while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
struct bdi_writeback_congested *congested =
rb_entry(rbn, struct bdi_writeback_congested, rb_node);
rb_erase(rbn, &bdi->cgwb_congested_tree);
congested->bdi = NULL; /* mark @congested unlinked */
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