linux-kernel - Re: [PATCH for-next 9/9] RDMA/hns: Fix different dgids mapping to the same dip

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Message-ID: <cd7ae683-c9b9-cb1c-c5fc-739d66c303ec@hisilicon.com>
Date: Thu, 17 Oct 2024 21:21:45 +0800
From: Junxian Huang <huangjunxian6@...ilicon.com>
To: Leon Romanovsky <leon@...nel.org>
CC: <jgg@...pe.ca>, <linux-rdma@...r.kernel.org>, <linuxarm@...wei.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH for-next 9/9] RDMA/hns: Fix different dgids mapping to the
 same dip_idx



On 2024/9/10 21:12, Leon Romanovsky wrote:
> On Fri, Sep 06, 2024 at 05:34:44PM +0800, Junxian Huang wrote:
>> From: Feng Fang <fangfeng4@...wei.com>
>>
>> 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 two new bitmaps: qpn_bitmap to record
>> QPN that is not being used as dip_idx, and dip_idx_map to record QPN
>> that is being used. Besides, introduce a reference count of a dip_idx
>> to indicate the number of QPs that using this dip_idx. When creating
>> a DIP QP, if it has a new dgid, set the corresponding bit in dip_idx_map,
>> otherwise add 1 to the reference count of the reused dip_idx and set bit
>> in qpn_bitmap. When destroying a DIP QP, decrement the reference count
>> by 1. If it becomes 0, set bit in qpn_bitmap and clear bit in dip_idx_map.
>>
>> Fixes: eb653eda1e91 ("RDMA/hns: Bugfix for incorrect association between dip_idx and dgid")
>> Fixes: f91696f2f053 ("RDMA/hns: Support congestion control type selection according to the FW")
>> Signed-off-by: Feng Fang <fangfeng4@...wei.com>
>> Signed-off-by: Junxian Huang <huangjunxian6@...ilicon.com>
>> ---
>>  drivers/infiniband/hw/hns/hns_roce_device.h |  6 +--
>>  drivers/infiniband/hw/hns/hns_roce_hw_v2.c  | 58 ++++++++++++++++++---
>>  drivers/infiniband/hw/hns/hns_roce_hw_v2.h  |  1 +
>>  drivers/infiniband/hw/hns/hns_roce_qp.c     | 16 ++++--
>>  4 files changed, 67 insertions(+), 14 deletions(-)
> 
> It is strange implementation, double bitmap and refcount looks like
> open-coding of some basic coding patterns. Let's wait with applying it
> for now.
> 

Hi Leon, it's been a while since this patch was sent. Is it okay to be applied?

Regarding your question about the double bitmaps, that's because we have 3 states
to track:
1) the context hasn't been created
2) the context has been created but not used as dip_ctx
3) the context is being used as dip_ctx.

Junxian

> Thanks
>