RDMA/hns: Fix different dgids mapping to the same dip_idx

DIP algorithm requires a one-to-one mapping between dgid and dip_idx.
Currently a queue 'spare_idx' is used to store QPN of QPs that use
DIP algorithm. For a new dgid, use a QPN from spare_idx as dip_idx.
This method lacks a mechanism for deduplicating QPN, which may result
in different dgids sharing the same dip_idx and break the one-to-one
mapping requirement.

This patch replaces spare_idx with xarray and introduces a refcnt of
a dip_idx to indicate the number of QPs that using this dip_idx.

The state machine for dip_idx management is implemented as:

* The entry at an index in xarray is empty -- This indicates that the
  corresponding dip_idx hasn't been created.

* The entry at an index in xarray is not empty but with 0 refcnt --
  This indicates that the corresponding dip_idx has been created but
  not used as dip_idx yet.

* The entry at an index in xarray is not empty and with non-0 refcnt --
  This indicates that the corresponding dip_idx is being used by refcnt
  number of DIP QPs.

Fixes: eb653eda ("RDMA/hns: Bugfix for incorrect association between dip_idx and dgid")
Fixes: f91696f2 ("RDMA/hns: Support congestion control type selection according to the FW")
Signed-off-by: Feng Fang <fangfeng4@huawei.com>
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://patch.msgid.link/20241112055553.3681129-1-huangjunxian6@hisilicon.com


Signed-off-by: Leon Romanovsky <leon@kernel.org>