smb: client: make sure we call ib_dma_unmap_single() only if we called ib_dma_map_single already

In case of failures either ib_dma_map_single() might not be called yet
or ib_dma_unmap_single() was already called.

We should make sure put_receive_buffer() only calls
ib_dma_unmap_single() if needed.

Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Fixes: f198186 ("CIFS: SMBD: Establish SMB Direct connection")
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: metze-samba

fs/smb/client/smbdirect.c

@@ -1057,6 +1057,7 @@ static int smbd_post_recv(
 	if (rc) {
 		ib_dma_unmap_single(sc->ib.dev, response->sge.addr,
 				    response->sge.length, DMA_FROM_DEVICE);
+		response->sge.length = 0;
 		smbd_disconnect_rdma_connection(info);
 		log_rdma_recv(ERR, "ib_post_recv failed rc=%d\n", rc);
 	}
@@ -1186,8 +1187,13 @@ static void put_receive_buffer(
 	struct smbdirect_socket *sc = &info->socket;
 	unsigned long flags;
 
-	ib_dma_unmap_single(sc->ib.dev, response->sge.addr,
-		response->sge.length, DMA_FROM_DEVICE);
+	if (likely(response->sge.length != 0)) {
+		ib_dma_unmap_single(sc->ib.dev,
+				    response->sge.addr,
+				    response->sge.length,
+				    DMA_FROM_DEVICE);
+		response->sge.length = 0;
+	}
 
 	spin_lock_irqsave(&info->receive_queue_lock, flags);
 	list_add_tail(&response->list, &info->receive_queue);
@@ -1221,6 +1227,7 @@ static int allocate_receive_buffers(struct smbd_connection *info, int num_buf)
 			goto allocate_failed;
 
 		response->info = info;
+		response->sge.length = 0;
 		list_add_tail(&response->list, &info->receive_queue);
 		info->count_receive_queue++;
 	}