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Commit e27c5b9d authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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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 <tj@kernel.org>
Reported-by: default avatarCody P Schafer <dev@codyps.com>
Fixes: a20135ff ("writeback: don't drain bdi_writeback_congested on bdi destruction")
Link: http://lkml.kernel.org/g/1443997973-1700-1-git-send-email-dev@codyps.com


Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 0dfc70c3

mm/backing-dev.c

+6 −4
Original line number Diff line number Diff line
@@ -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)

		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 */

	}