CIFS: Do not assume one credit for async responses

If we don't receive a response we can't assume that the server
granted one credit. Assume zero credits in such cases.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2pdu.c

@@ -2924,9 +2924,10 @@ smb2_echo_callback(struct mid_q_entry *mid)
 {
 	struct TCP_Server_Info *server = mid->callback_data;
 	struct smb2_echo_rsp *rsp = (struct smb2_echo_rsp *)mid->resp_buf;
-	unsigned int credits_received = 1;
+	unsigned int credits_received = 0;
 
-	if (mid->mid_state == MID_RESPONSE_RECEIVED)
+	if (mid->mid_state == MID_RESPONSE_RECEIVED
+	    || mid->mid_state == MID_RESPONSE_MALFORMED)
 		credits_received = le16_to_cpu(rsp->sync_hdr.CreditRequest);
 
 	DeleteMidQEntry(mid);
@@ -3183,7 +3184,7 @@ smb2_readv_callback(struct mid_q_entry *mid)
 	struct TCP_Server_Info *server = tcon->ses->server;
 	struct smb2_sync_hdr *shdr =
 				(struct smb2_sync_hdr *)rdata->iov[0].iov_base;
-	unsigned int credits_received = 1;
+	unsigned int credits_received = 0;
 	struct smb_rqst rqst = { .rq_iov = rdata->iov,
 				 .rq_nvec = 2,
 				 .rq_pages = rdata->pages,
@@ -3222,6 +3223,9 @@ smb2_readv_callback(struct mid_q_entry *mid)
 		task_io_account_read(rdata->got_bytes);
 		cifs_stats_bytes_read(tcon, rdata->got_bytes);
 		break;
+	case MID_RESPONSE_MALFORMED:
+		credits_received = le16_to_cpu(shdr->CreditRequest);
+		/* fall through */
 	default:
 		if (rdata->result != -ENODATA)
 			rdata->result = -EIO;
@@ -3407,7 +3411,7 @@ smb2_writev_callback(struct mid_q_entry *mid)
 	struct cifs_tcon *tcon = tlink_tcon(wdata->cfile->tlink);
 	unsigned int written;
 	struct smb2_write_rsp *rsp = (struct smb2_write_rsp *)mid->resp_buf;
-	unsigned int credits_received = 1;
+	unsigned int credits_received = 0;
 
 	switch (mid->mid_state) {
 	case MID_RESPONSE_RECEIVED:
@@ -3435,6 +3439,9 @@ smb2_writev_callback(struct mid_q_entry *mid)
 	case MID_RETRY_NEEDED:
 		wdata->result = -EAGAIN;
 		break;
+	case MID_RESPONSE_MALFORMED:
+		credits_received = le16_to_cpu(rsp->sync_hdr.CreditRequest);
+		/* fall through */
 	default:
 		wdata->result = -EIO;
 		break;