btrfs: fix reloc root leak with 0 ref reloc roots on recovery

When recovering a relocation, if we run into a reloc root that has 0
refs we simply add it to the reloc_control->reloc_roots list, and then
clean it up later.  The problem with this is __del_reloc_root() doesn't
do anything if the root isn't in the radix tree, which in this case it
won't be because we never call __add_reloc_root() on the reloc_root.

This exit condition simply isn't correct really.  During normal
operation we can remove ourselves from the rb tree and then we're meant
to clean up later at merge_reloc_roots() time, and this happens
correctly.  During recovery we're depending on free_reloc_roots() to
drop our references, but we're short-circuiting.

Fix this by continuing to check if we're on the list and dropping
ourselves from the reloc_control root list and dropping our reference
appropriately.  Change the corresponding BUG_ON() to an ASSERT() that
does the correct thing if we aren't in the rb tree.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 9f2289bcdde61e45feaa1f30f4b833e0397bd8d7..d29baf3822a7c89982f7ed0c7c07d7467a1f59e5 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -669,9 +669,7 @@ static void __del_reloc_root(struct btrfs_root *root)
                        RB_CLEAR_NODE(&node->rb_node);
                }
                spin_unlock(&rc->reloc_root_tree.lock);
-               if (!node)
-                       return;
-               BUG_ON((struct btrfs_root *)node->data != root);
+               ASSERT(!node || (struct btrfs_root *)node->data == root);
        }
 
        /*