nvmet-tcp: fix incomplete data digest send

Current nvmet_try_send_ddgst() code does not check whether
all data digest bytes are transmitted, fix this by returning
-EAGAIN if all data digest bytes are not transmitted.

Fixes: 872d26a ("nvmet-tcp: add NVMe over TCP target driver")
Signed-off-by: Varun Prakash <varun@chelsio.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/tcp.c

@@ -711,10 +711,11 @@ static int nvmet_try_send_r2t(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
 static int nvmet_try_send_ddgst(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
 {
 	struct nvmet_tcp_queue *queue = cmd->queue;
+	int left = NVME_TCP_DIGEST_LENGTH - cmd->offset;
 	struct msghdr msg = { .msg_flags = MSG_DONTWAIT };
 	struct kvec iov = {
 		.iov_base = (u8 *)&cmd->exp_ddgst + cmd->offset,
-		.iov_len = NVME_TCP_DIGEST_LENGTH - cmd->offset
+		.iov_len = left
 	};
 	int ret;
 
@@ -728,6 +729,10 @@ static int nvmet_try_send_ddgst(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
 		return ret;
 
 	cmd->offset += ret;
+	left -= ret;
+
+	if (left)
+		return -EAGAIN;
 
 	if (queue->nvme_sq.sqhd_disabled) {
 		cmd->queue->snd_cmd = NULL;