a20135ffbc44 ("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: Tejun Heo <t...@kernel.org>
Reported-by: Cody P Schafer <d...@codyps.com>
Fixes: a20135ffbc44 ("writeback: don't drain bdi_writeback_congested on bdi
destruction")
Link: http://lkml.kernel.org/g/1443997973-1700-1-git-send-email-...@codyps.com
---
mm/backing-dev.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -681,7 +681,7 @@ static int cgwb_bdi_init(struct backing_
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 back
radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
cgwb_kill(*slot);
- 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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