IB/core: Make ib_dealloc_pd return void

The majority of callers never check the return value, and even if they
did, they can't do anything about a failure.

All possible failure cases represent a bug in the caller, so just
WARN_ON inside the function instead.

This fixes a few random errors:
net/rd/iw.c infinite loops while it fails. (racing with EBUSY?)

This also lays the ground work to get rid of error return from the
drivers. Most drivers do not error, the few that do are broken since
it cannot be handled.

Since uverbs can legitimately make use of EBUSY, open code the
check.

Signed-off-by: Jason Gunthorpe <[e-mail]>
Reviewed-by: Chuck Lever <[e-mail]>
Signed-off-by: Doug Ledford <[e-mail]>

drivers/infiniband/core/uverbs_cmd.c

···
 {
 	struct ib_uverbs_dealloc_pd cmd;
 	struct ib_uobject          *uobj;
+	struct ib_pd		   *pd;
 	int                         ret;
 
 	if (copy_from_user(&cmd, buf, sizeof cmd))
···
 	uobj = idr_write_uobj(&ib_uverbs_pd_idr, cmd.pd_handle, file->ucontext);
 	if (!uobj)
 		return -EINVAL;
+	pd = uobj->object;
 
-	ret = ib_dealloc_pd(uobj->object);
-	if (!ret)
-		uobj->live = 0;
+	if (atomic_read(&pd->usecnt)) {
+		ret = -EBUSY;
+		goto err_put;
+	}
 
-	put_uobj_write(uobj);
-
+	ret = pd->device->dealloc_pd(uobj->object);
+	WARN_ONCE(ret, "Infiniband HW driver failed dealloc_pd");
 	if (ret)
-		return ret;
+		goto err_put;
+
+	uobj->live = 0;
+	put_uobj_write(uobj);
 
 	idr_remove_uobj(&ib_uverbs_pd_idr, uobj);
 
···
 	put_uobj(uobj);
 
 	return in_len;
+
+err_put:
+	put_uobj_write(uobj);
+	return ret;
 }
 
 struct xrcd_table_entry {

drivers/infiniband/core/verbs.c

···
 }
 EXPORT_SYMBOL(ib_alloc_pd);
 
-int ib_dealloc_pd(struct ib_pd *pd)
+/**
+ * ib_dealloc_pd - Deallocates a protection domain.
+ * @pd: The protection domain to deallocate.
+ *
+ * It is an error to call this function while any resources in the pd still
+ * exist.  The caller is responsible to synchronously destroy them and
+ * guarantee no new allocations will happen.
+ */
+void ib_dealloc_pd(struct ib_pd *pd)
 {
+	int ret;
+
 	if (pd->local_mr) {
-		if (ib_dereg_mr(pd->local_mr))
-			return -EBUSY;
+		ret = ib_dereg_mr(pd->local_mr);
+		WARN_ON(ret);
 		pd->local_mr = NULL;
 	}
 
-	if (atomic_read(&pd->usecnt))
-		return -EBUSY;
+	/* uverbs manipulates usecnt with proper locking, while the kabi
+	   requires the caller to guarantee we can't race here. */
+	WARN_ON(atomic_read(&pd->usecnt));
 
-	return pd->device->dealloc_pd(pd);
+	/* Making delalloc_pd a void return is a WIP, no driver should return
+	   an error here. */
+	ret = pd->device->dealloc_pd(pd);
+	WARN_ONCE(ret, "Infiniband HW driver failed dealloc_pd");
 }
 EXPORT_SYMBOL(ib_dealloc_pd);
 

drivers/infiniband/ulp/ipoib/ipoib_verbs.c

···
 		priv->wq = NULL;
 	}
 
-	if (ib_dealloc_pd(priv->pd))
-		ipoib_warn(priv, "ib_dealloc_pd failed\n");
-
+	ib_dealloc_pd(priv->pd);
 }
 
 void ipoib_event(struct ib_event_handler *handler,

drivers/infiniband/ulp/iser/iser_verbs.c

···
 
 	(void)ib_unregister_event_handler(&device->event_handler);
 	(void)ib_dereg_mr(device->mr);
-	(void)ib_dealloc_pd(device->pd);
+	ib_dealloc_pd(device->pd);
 
 	kfree(device->comps);
 	device->comps = NULL;

include/rdma/ib_verbs.h

···
 
 struct ib_pd *ib_alloc_pd(struct ib_device *device);
 
-/**
- * ib_dealloc_pd - Deallocates a protection domain.
- * @pd: The protection domain to deallocate.
- */
-int ib_dealloc_pd(struct ib_pd *pd);
+void ib_dealloc_pd(struct ib_pd *pd);
 
 /**
  * ib_create_ah - Creates an address handle for the given address vector.

net/rds/iw.c

···
 	if (rds_iwdev->mr)
 		ib_dereg_mr(rds_iwdev->mr);
 
-	while (ib_dealloc_pd(rds_iwdev->pd)) {
-		rdsdebug("Failed to dealloc pd %p\n", rds_iwdev->pd);
-		msleep(1);
-	}
+	ib_dealloc_pd(rds_iwdev->pd);
 
 	list_del(&rds_iwdev->list);
 	kfree(rds_iwdev);

net/sunrpc/xprtrdma/verbs.c

···
 
 	/* If the pd is still busy, xprtrdma missed freeing a resource */
 	if (ia->ri_pd && !IS_ERR(ia->ri_pd))
-		WARN_ON(ib_dealloc_pd(ia->ri_pd));
+		ib_dealloc_pd(ia->ri_pd);
 }
 
 /*