On 5/10/2019 6:02 AM, Jason Gunthorpe wrote:

On Mon, Apr 29, 2019 at 04:37:20PM -0700, Santosh Shilimkar wrote:

quoted

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 <redacted>
Reviewed-tested-by: Zhu Yanjun [off-list ref]
Signed-off-by: Hans Westgaard Ry <redacted>
Signed-off-by: Santosh Shilimkar <redacted>
  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