Re: [net-next][PATCH v2 2/2] rds: add sysctl for rds support of On-Demand-Paging

[Santosh Shilimkar <santosh.shilimkar@oracle.com>]

On 5/10/2019 6:02 AM, Jason Gunthorpe wrote:
> On Mon, Apr 29, 2019 at 04:37:20PM -0700, Santosh Shilimkar wrote:
>> RDS doesn't support RDMA on memory apertures that require On Demand
>> Paging (ODP), such as FS DAX memory. A sysctl is added to indicate
>> whether RDMA requiring ODP is supported.
>>
>> Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
>> Reviewed-tested-by: Zhu Yanjun <yanjun.zhu@oracle.com>
>> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
>>   net/rds/ib.h        | 1 +
>>   net/rds/ib_sysctl.c | 8 ++++++++
>>   2 files changed, 9 insertions(+)
>>
>> diff --git a/net/rds/ib.h b/net/rds/ib.h
>> index 67a715b..80e11ef 100644
>> +++ b/net/rds/ib.h
>> @@ -457,5 +457,6 @@ unsigned int rds_ib_stats_info_copy(struct rds_info_iterator *iter,
>>   extern unsigned long rds_ib_sysctl_max_unsig_bytes;
>>   extern unsigned long rds_ib_sysctl_max_recv_allocation;
>>   extern unsigned int rds_ib_sysctl_flow_control;
>> +extern unsigned int rds_ib_sysctl_odp_support;
>>   
>>   #endif
>> diff --git a/net/rds/ib_sysctl.c b/net/rds/ib_sysctl.c
>> index e4e41b3..7cc02cd 100644
>> +++ b/net/rds/ib_sysctl.c
>> @@ -60,6 +60,7 @@
>>    * will cause credits to be added before protocol negotiation.
>>    */
>>   unsigned int rds_ib_sysctl_flow_control = 0;
>> +unsigned int rds_ib_sysctl_odp_support;
>>   
>>   static struct ctl_table rds_ib_sysctl_table[] = {
>>   	{
>> @@ -103,6 +104,13 @@
>>   		.mode		= 0644,
>>   		.proc_handler	= proc_dointvec,
>>   	},
>> +	{
>> +		.procname       = "odp_support",
>> +		.data           = &rds_ib_sysctl_odp_support,
>> +		.maxlen         = sizeof(rds_ib_sysctl_odp_support),
>> +		.mode           = 0444,
>> +		.proc_handler   = proc_dointvec,
>> +	},
>>   	{ }
>>   };
> 
> using a read-only sysctl as a capability negotiation scheme seems
> horrible to me
>
Do you have a suggestion ? Was thinking of adding a socketopt but
didn't pursue it further.

Regards,
Santosh