virtio-mem: Use -ETXTBSY as error code if the device is busy

Let's be able to distinguish if the device or if memory is busy.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20200507140139.17083-15-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_mem.c

@@ -893,7 +893,7 @@ static int virtio_mem_send_plug_request(struct virtio_mem *vm, uint64_t addr,
 	case VIRTIO_MEM_RESP_NACK:
 		return -EAGAIN;
 	case VIRTIO_MEM_RESP_BUSY:
-		return -EBUSY;
+		return -ETXTBSY;
 	case VIRTIO_MEM_RESP_ERROR:
 		return -EINVAL;
 	default:
@@ -919,7 +919,7 @@ static int virtio_mem_send_unplug_request(struct virtio_mem *vm, uint64_t addr,
 		vm->plugged_size -= size;
 		return 0;
 	case VIRTIO_MEM_RESP_BUSY:
-		return -EBUSY;
+		return -ETXTBSY;
 	case VIRTIO_MEM_RESP_ERROR:
 		return -EINVAL;
 	default:
@@ -941,7 +941,7 @@ static int virtio_mem_send_unplug_all_request(struct virtio_mem *vm)
 		atomic_set(&vm->config_changed, 1);
 		return 0;
 	case VIRTIO_MEM_RESP_BUSY:
-		return -EBUSY;
+		return -ETXTBSY;
 	default:
 		return -ENOMEM;
 	}
@@ -1557,11 +1557,15 @@ static void virtio_mem_run_wq(struct work_struct *work)
 		 * or we have too many offline memory blocks.
 		 */
 		break;
-	case -EBUSY:
+	case -ETXTBSY:
 		/*
 		 * The hypervisor cannot process our request right now
-		 * (e.g., out of memory, migrating) or we cannot free up
-		 * any memory to unplug it (all plugged memory is busy).
+		 * (e.g., out of memory, migrating);
+		 */
+	case -EBUSY:
+		/*
+		 * We cannot free up any memory to unplug it (all plugged memory
+		 * is busy).
 		 */
 	case -ENOMEM:
 		/* Out of memory, try again later. */