Re: [PATCH 4/8] btrfs: free the reloc_control in a consistent way

[David Sterba <dsterba@suse.cz>]

On Fri, Mar 13, 2020 at 11:44:44AM -0400, Josef Bacik wrote:
> If we have an error while processing the reloc roots we could leak roots
> that were added to rc->reloc_roots before we hit the error.  We could
> have also not removed the reloct tree mapping from our rb_tree, so clean
> up any remaining nodes in the reloc root rb_tree.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
>  fs/btrfs/relocation.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index c496f8ed8c7e..721d049ff2b5 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -4387,6 +4387,20 @@ static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
>  	return rc;
>  }
>  
> +static void free_reloc_control(struct reloc_control *rc)
> +{
> +	struct mapping_node *node, *tmp;
> +
> +	free_reloc_roots(&rc->reloc_roots);
> +	rbtree_postorder_for_each_entry_safe(node, tmp,
> +					     &rc->reloc_root_tree.rb_root,
> +					     rb_node) {
> +		rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);

The rb_erase is not needed here, the postorder traversal just goes over
all nodes and allows to free the containing structures together with the
rb_node. Dangling pointers are not an issue.

> +		kfree(node);
> +	}
> +	kfree(rc);
> +}