RDMA/core: Export ib_open_qp() to share XRC TGT QPs

XRC TGT QPs are shared resources among multiple processes.  Since the
creating process may exit, allow other processes which share the same
XRC domain to open an existing QP.  This allows us to transfer
ownership of an XRC TGT QP to another process.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 24 insertions, 6 deletions

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index dfd9b87b7ffd..8705539bce75 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -605,6 +605,13 @@ struct ib_qp_init_attr {
         u8                      port_num; /* special QP types only */
 };
 
+struct ib_qp_open_attr {
+        void                  (*event_handler)(struct ib_event *, void *);
+        void                   *qp_context;
+        u32                     qp_num;
+        enum ib_qp_type         qp_type;
+};
+
 enum ib_rnr_timeout {
         IB_RNR_TIMER_655_36 =  0,
         IB_RNR_TIMER_000_01 =  1,
@@ -932,6 +939,9 @@ struct ib_qp {
         struct ib_srq          *srq;
         struct ib_xrcd         *xrcd; /* XRC TGT QPs only */
         struct list_head        xrcd_list;
+        atomic_t                usecnt; /* count times opened */
+        struct list_head        open_list;
+        struct ib_qp           *real_qp;
         struct ib_uobject      *uobject;
         void                  (*event_handler)(struct ib_event *, void *);
         void                   *qp_context;
@@ -1488,15 +1498,23 @@ int ib_query_qp(struct ib_qp *qp,
 int ib_destroy_qp(struct ib_qp *qp);
 
 /**
- * ib_release_qp - Release an external reference to a QP.
+ * ib_open_qp - Obtain a reference to an existing sharable QP.
+ * @xrcd - XRC domain
+ * @qp_open_attr: Attributes identifying the QP to open.
+ *
+ * Returns a reference to a sharable QP.
+ */
+struct ib_qp *ib_open_qp(struct ib_xrcd *xrcd,
+                         struct ib_qp_open_attr *qp_open_attr);
+
+/**
+ * ib_close_qp - Release an external reference to a QP.
  * @qp: The QP handle to release
  *
- * The specified QP handle is released by the caller.  If the QP is
- * referenced internally, it is not destroyed until all internal
- * references are released.  After releasing the qp, the caller
- * can no longer access it and all events on the QP are discarded.
+ * The opened QP handle is released by the caller.  The underlying
+ * shared QP is not destroyed until all internal references are released.
  */
-int ib_release_qp(struct ib_qp *qp);
+int ib_close_qp(struct ib_qp *qp);
 
 /**
  * ib_post_send - Posts a list of work requests to the send queue of