IB/rdmavt: Correct qp_priv_alloc() return value test

The current drivers return errors from this calldown
wrapped in an ERR_PTR().

The rdmavt code incorrectly tests for NULL.

The code is fixed to use IS_ERR() and change ret according
to the driver return value.

Cc: Stable <stable@vger.kernel.org> # 4.6+
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/sw/rdmavt/qp.c

@@ -699,8 +699,10 @@ struct ib_qp *rvt_create_qp(struct ib_pd *ibpd,
 		 * initialization that is needed.
 		 */
 		priv = rdi->driver_f.qp_priv_alloc(rdi, qp, gfp);
-		if (!priv)
+		if (IS_ERR(priv)) {
+			ret = priv;
 			goto bail_qp;
+		}
 		qp->priv = priv;
 		qp->timeout_jiffies =
 			usecs_to_jiffies((4096UL * (1UL << qp->timeout)) /

include/rdma/rdma_vt.h

@@ -203,7 +203,9 @@ struct rvt_driver_provided {
 
 	/*
 	 * Allocate a private queue pair data structure for driver specific
-	 * information which is opaque to rdmavt.
+	 * information which is opaque to rdmavt.  Errors are returned via
+	 * ERR_PTR(err).  The driver is free to return NULL or a valid
+	 * pointer.
 	 */
 	void * (*qp_priv_alloc)(struct rvt_dev_info *rdi, struct rvt_qp *qp,
 				gfp_t gfp);