xen/xenbus: let xenbus_map_ring_valloc() return errno values only

Today xenbus_map_ring_valloc() can return either a negative errno
value (-ENOMEM or -EINVAL) or a grant status value. This is a mess as
e.g -ENOMEM and GNTST_eagain have the same numeric value.

Fix that by turning all grant mapping errors into -ENOENT. This is
no problem as all callers of xenbus_map_ring_valloc() only use the
return value to print an error message, and in case of mapping errors
the grant status value has already been printed by __xenbus_map_ring()
before.

Signed-off-by: Juergen Gross <[e-mail]>
Reviewed-by: Boris Ostrovsky <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Boris Ostrovsky <[e-mail]>

drivers/xen/xenbus/xenbus_client.c

···
  * Map @nr_grefs pages of memory into this domain from another
  * domain's grant table.  xenbus_map_ring_valloc allocates @nr_grefs
  * pages of virtual address space, maps the pages to that address, and
- * sets *vaddr to that address.  Returns 0 on success, and GNTST_*
- * (see xen/include/interface/grant_table.h) or -ENOMEM / -EINVAL on
+ * sets *vaddr to that address.  Returns 0 on success, and -errno on
  * error. If an error is returned, device will switch to
  * XenbusStateClosing and the error message will be saved in XenStore.
  */
···
 		return -ENOMEM;
 
 	info->node = kzalloc(sizeof(*info->node), GFP_KERNEL);
-	if (!info->node) {
+	if (!info->node)
 		err = -ENOMEM;
-		goto out;
-	}
+	else
+		err = ring_ops->map(dev, info, gnt_refs, nr_grefs, vaddr);
 
-	err = ring_ops->map(dev, info, gnt_refs, nr_grefs, vaddr);
-
-	/* Some hypervisors are buggy and can return 1. */
-	if (err > 0)
-		err = GNTST_general_error;
-
- out:
 	kfree(info->node);
 	kfree(info);
 	return err;
···
 			     bool *leaked)
 {
 	int i, j;
-	int err = GNTST_okay;
 
 	if (nr_grefs > XENBUS_MAX_RING_GRANTS)
 		return -EINVAL;
···
 
 	for (i = 0; i < nr_grefs; i++) {
 		if (info->map[i].status != GNTST_okay) {
-			err = info->map[i].status;
 			xenbus_dev_fatal(dev, info->map[i].status,
 					 "mapping in shared page %d from domain %d",
 					 gnt_refs[i], dev->otherend_id);
···
 			handles[i] = info->map[i].handle;
 	}
 
-	return GNTST_okay;
+	return 0;
 
  fail:
 	for (i = j = 0; i < nr_grefs; i++) {
···
 		}
 	}
 
-	return err;
+	return -ENOENT;
 }
 
 /**