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

[Jason Gunthorpe <jgg@ziepe.ca>]

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

Jason