btrfs: fix memory leak in update_space_info failure path

BugLink: http://bugs.launchpad.net/bugs/1698799

commit 896533a7 upstream.

If we fail to add the space_info kobject, we'll leak the memory
for the percpu counter.

Fixes: 6ab0a202 (btrfs: publish allocation data in sysfs)
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

fs/btrfs/extent-tree.c

@@ -3854,6 +3854,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
 				    info->space_info_kobj, "%s",
 				    alloc_name(found->flags));
 	if (ret) {
+		percpu_counter_destroy(&found->total_bytes_pinned);
 		kfree(found);
 		return ret;
 	}