smb: client: port and use the wait_for_credits logic used by server

This simplifies the logic and prepares the use of
smbdirect_send_batch in order to make sure
all messages in a multi fragment send are grouped
together.

We'll add the smbdirect_send_batch processin
in a later patch.

Cc: <stable@vger.kernel.org> # 6.18.x
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: metze-samba

fs/smb/client/smbdirect.c

@@ -1137,6 +1137,44 @@ static int smbd_post_send(struct smbdirect_socket *sc,
 	return rc;
 }
 
+static int wait_for_credits(struct smbdirect_socket *sc,
+			    wait_queue_head_t *waitq, atomic_t *total_credits,
+			    int needed)
+{
+	int ret;
+
+	do {
+		if (atomic_sub_return(needed, total_credits) >= 0)
+			return 0;
+
+		atomic_add(needed, total_credits);
+		ret = wait_event_interruptible(*waitq,
+					       atomic_read(total_credits) >= needed ||
+					       sc->status != SMBDIRECT_SOCKET_CONNECTED);
+
+		if (sc->status != SMBDIRECT_SOCKET_CONNECTED)
+			return -ENOTCONN;
+		else if (ret < 0)
+			return ret;
+	} while (true);
+}
+
+static int wait_for_send_lcredit(struct smbdirect_socket *sc)
+{
+	return wait_for_credits(sc,
+				&sc->send_io.lcredits.wait_queue,
+				&sc->send_io.lcredits.count,
+				1);
+}
+
+static int wait_for_send_credits(struct smbdirect_socket *sc)
+{
+	return wait_for_credits(sc,
+				&sc->send_io.credits.wait_queue,
+				&sc->send_io.credits.count,
+				1);
+}
+
 static int smbd_post_send_iter(struct smbdirect_socket *sc,
 			       struct iov_iter *iter,
 			       int *_remaining_data_length)
@@ -1149,41 +1187,19 @@ static int smbd_post_send_iter(struct smbdirect_socket *sc,
 	struct smbdirect_data_transfer *packet;
 	int new_credits = 0;
 
-wait_lcredit:
-	/* Wait for local send credits */
-	rc = wait_event_interruptible(sc->send_io.lcredits.wait_queue,
-		atomic_read(&sc->send_io.lcredits.count) > 0 ||
-		sc->status != SMBDIRECT_SOCKET_CONNECTED);
-	if (rc)
-		goto err_wait_lcredit;
-
-	if (sc->status != SMBDIRECT_SOCKET_CONNECTED) {
-		log_outgoing(ERR, "disconnected not sending on wait_credit\n");
+	rc = wait_for_send_lcredit(sc);
+	if (rc) {
+		log_outgoing(ERR, "disconnected not sending on wait_lcredit\n");
 		rc = -EAGAIN;
 		goto err_wait_lcredit;
 	}
-	if (unlikely(atomic_dec_return(&sc->send_io.lcredits.count) < 0)) {
-		atomic_inc(&sc->send_io.lcredits.count);
-		goto wait_lcredit;
-	}
 
-wait_credit:
-	/* Wait for send credits. A SMBD packet needs one credit */
-	rc = wait_event_interruptible(sc->send_io.credits.wait_queue,
-		atomic_read(&sc->send_io.credits.count) > 0 ||
-		sc->status != SMBDIRECT_SOCKET_CONNECTED);
-	if (rc)
-		goto err_wait_credit;
-
-	if (sc->status != SMBDIRECT_SOCKET_CONNECTED) {
+	rc = wait_for_send_credits(sc);
+	if (rc) {
 		log_outgoing(ERR, "disconnected not sending on wait_credit\n");
 		rc = -EAGAIN;
 		goto err_wait_credit;
 	}
-	if (unlikely(atomic_dec_return(&sc->send_io.credits.count) < 0)) {
-		atomic_inc(&sc->send_io.credits.count);
-		goto wait_credit;
-	}
 
 	request = mempool_alloc(sc->send_io.mem.pool, GFP_KERNEL);
 	if (!request) {