RDMA/core: Add XRC SRQ type

XRC ("eXtended reliable connected") is an IB transport that provides
better scalability by allowing senders to specify which shared receive
queue (SRQ) should be used to receive a message, which essentially
allows one transport context (QP connection) to serve multiple
destinations (as long as they share an adapter, of course).

XRC defines SRQs that are specifically used by XRC connections.  Expand
the SRQ code to support XRC SRQs.  An XRC SRQ is currently restricted to
only XRC use according to the IB XRC Annex.

Portions of this patch were derived from work by
Jack Morgenstein <jackm@dev.mellanox.co.il>.
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/core/verbs.c

@@ -251,6 +251,12 @@ struct ib_srq *ib_create_srq(struct ib_pd *pd,
 		srq->event_handler = srq_init_attr->event_handler;
 		srq->srq_context   = srq_init_attr->srq_context;
 		srq->srq_type      = srq_init_attr->srq_type;
+		if (srq->srq_type == IB_SRQT_XRC) {
+			srq->ext.xrc.xrcd = srq_init_attr->ext.xrc.xrcd;
+			srq->ext.xrc.cq   = srq_init_attr->ext.xrc.cq;
+			atomic_inc(&srq->ext.xrc.xrcd->usecnt);
+			atomic_inc(&srq->ext.xrc.cq->usecnt);
+		}
 		atomic_inc(&pd->usecnt);
 		atomic_set(&srq->usecnt, 0);
 	}
@@ -280,16 +286,29 @@ EXPORT_SYMBOL(ib_query_srq);
 int ib_destroy_srq(struct ib_srq *srq)
 {
 	struct ib_pd *pd;
+	enum ib_srq_type srq_type;
+	struct ib_xrcd *uninitialized_var(xrcd);
+	struct ib_cq *uninitialized_var(cq);
 	int ret;
 
 	if (atomic_read(&srq->usecnt))
 		return -EBUSY;
 
 	pd = srq->pd;
+	srq_type = srq->srq_type;
+	if (srq_type == IB_SRQT_XRC) {
+		xrcd = srq->ext.xrc.xrcd;
+		cq = srq->ext.xrc.cq;
+	}
 
 	ret = srq->device->destroy_srq(srq);
-	if (!ret)
+	if (!ret) {
 		atomic_dec(&pd->usecnt);
+		if (srq_type == IB_SRQT_XRC) {
+			atomic_dec(&xrcd->usecnt);
+			atomic_dec(&cq->usecnt);
+		}
+	}
 
 	return ret;
 }

include/rdma/ib_verbs.h

@@ -524,7 +524,8 @@ enum ib_cq_notify_flags {
 };
 
 enum ib_srq_type {
-	IB_SRQT_BASIC
+	IB_SRQT_BASIC,
+	IB_SRQT_XRC
 };
 
 enum ib_srq_attr_mask {
@@ -543,6 +544,13 @@ struct ib_srq_init_attr {
 	void		       *srq_context;
 	struct ib_srq_attr	attr;
 	enum ib_srq_type	srq_type;
+
+	union {
+		struct {
+			struct ib_xrcd *xrcd;
+			struct ib_cq   *cq;
+		} xrc;
+	} ext;
 };
 
 struct ib_qp_cap {
@@ -895,6 +903,14 @@ struct ib_srq {
 	void		       *srq_context;
 	enum ib_srq_type	srq_type;
 	atomic_t		usecnt;
+
+	union {
+		struct {
+			struct ib_xrcd *xrcd;
+			struct ib_cq   *cq;
+			u32		srq_num;
+		} xrc;
+	} ext;
 };
 
 struct ib_qp {