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    Subject[PATCH 4.4 73/93] btrfs: fix reloc root leak with 0 ref reloc roots on recovery
    Date
    From: Josef Bacik <josef@toxicpanda.com>

    commit c78a10aebb275c38d0cfccae129a803fe622e305 upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/btrfs/relocation.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    --- a/fs/btrfs/relocation.c
    +++ b/fs/btrfs/relocation.c
    @@ -1328,9 +1328,7 @@ static void __del_reloc_root(struct btrf
    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);
    }

    spin_lock(&root->fs_info->trans_lock);

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