Re: [PATCH 1/1] net: rds: add service level support in rds-info

[Zhu Yanjun <yanjun.zhu@oracle.com>]

Hi，Doug

My reply is in line.

On 2019/8/20 23:28, Doug Ledford wrote:
> On Mon, 2019-08-19 at 20:52 -0400, Zhu Yanjun wrote:
>> diff --git a/include/uapi/linux/rds.h b/include/uapi/linux/rds.h
>> index fd6b5f6..cba368e 100644
>> --- a/include/uapi/linux/rds.h
>> +++ b/include/uapi/linux/rds.h
>> @@ -250,6 +250,7 @@ struct rds_info_rdma_connection {
>>          __u32           rdma_mr_max;
>>          __u32           rdma_mr_size;
>>          __u8            tos;
>> +       __u8            sl;
>>          __u32           cache_allocs;
>>   };
>>   
>> @@ -265,6 +266,7 @@ struct rds6_info_rdma_connection {
>>          __u32           rdma_mr_max;
>>          __u32           rdma_mr_size;
>>          __u8            tos;
>> +       __u8            sl;
>>          __u32           cache_allocs;
>>   };
>>   
> This is a user space API break (as was the prior patch mentioned
> below)...
>
>> The commit fe3475af3bdf ("net: rds: add per rds connection cache
>> statistics") adds cache_allocs in struct rds_info_rdma_connection
>> as below:
>> struct rds_info_rdma_connection {
>> ...
>>          __u32           rdma_mr_max;
>>          __u32           rdma_mr_size;
>>          __u8            tos;
>>          __u32           cache_allocs;
>>   };
>> The peer struct in rds-tools of struct rds_info_rdma_connection is as
>> below:
>> struct rds_info_rdma_connection {
>> ...
>>          uint32_t        rdma_mr_max;
>>          uint32_t        rdma_mr_size;
>>          uint8_t         tos;
>>          uint8_t         sl;
>>          uint32_t        cache_allocs;
>> };
> Why are the user space rds tools not using the kernel provided abi
> files?
Perhaps it is a long story.
>
> In order to know if this ABI breakage is safe, we need to know what
> versions of rds-tools are out in the wild and have their own headers
> that we need to match up with.

 From my works in LAB and in the customer's host, rds-tools 2.0.7 is the 
popular

version. Other versions rds-tools are used less.

>    Are there any versions of rds-tools that
> actually use the kernel provided headers?

"the kernel provided headers", do you mean include/uapi/linux/rds.h?

I checked the rds-tools source code. I do not find any version of 
rds-tools us this header files.

> Are there any other users of
> uapi/linux/rds.h besides rds-tools?

Not sure. But in Oracle, there are some rds applications. I am not sure 
whether these rds applications

will use include/uapi/linux/rds.h file or not.

I will investigate it.

>
> Once the kernel and rds-tools package are in sync,

After this commit is merged into mailine, the kernel and rds-tools 
package are in sync.

I will make investigations about rds-tools using the kernel header 
include/uapi/linux/rds.h.

Thanks a lot for your comments.

Zhu Yanjun

>   rds-tools needs to be
> modified to use the kernel header and proper ABI maintenance needs to be
> started.
>