[PATCH] Fix sendonly join going away after Reregister event

[Christoph Lameter <cl@linux.com>]

From: Christoph Lameter <cl@linux.com>
Subject: [PATCH] Fix sendonly join going away after Reregister event

When a server receives a REREG event then the SM information in
the kernel is marked as invalid and a request is sent to the SM to update
the information.

However, receiving a REREG also occurs in user space applications that
are now trying to rejoin the multicast groups.

If the SM information is invalid then ib_sa_sendonly_fullmem_support()
returns false. That is wrong because it just means that we do not know
yet if the potentially new SM supports sendonly joins. It does not mean
that the SM does not support Sendonly joins.

This patch simply attempts to waits until the SM information is updated
and the determination can be made.

The code has not been testet but compiles fine.
I am not sure if it is good to do an msleep here.

Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/drivers/infiniband/core/sa_query.c
===================================================================
--- linux.orig/drivers/infiniband/core/sa_query.c	2020-12-17 14:51:15.301206041 +0000
+++ linux/drivers/infiniband/core/sa_query.c	2021-01-21 12:52:53.577943481 +0000
@@ -1963,11 +1963,19 @@ bool ib_sa_sendonly_fullmem_support(stru
 	if (!sa_dev)
 		return ret;

+redo:
 	port  = &sa_dev->port[port_num - sa_dev->start_port];

+	while (!port->classport_info.valid)
+		msleep(100);
+
 	spin_lock_irqsave(&port->classport_lock, flags);
-	if ((port->classport_info.valid) &&
-	    (port->classport_info.data.type == RDMA_CLASS_PORT_INFO_IB))
+	if (!port->classport_info.valid) {
+		/* Need to wait until the SM data is available */
+		spin_unlock_irqrestore(&port->classport_lock, flags);
+		goto redo;
+	}
+	if ((port->classport_info.data.type == RDMA_CLASS_PORT_INFO_IB))
 		ret = ib_get_cpi_capmask2(&port->classport_info.data.ib)
 			& IB_SA_CAP_MASK2_SENDONLY_FULL_MEM_SUPPORT;
 	spin_unlock_irqrestore(&port->classport_lock, flags);