cifs: try harder to open new channels

Previously we would only loop over the iface list once.
This patch tries to loop over multiple times until all channels are
opened. It will also try to reuse RSS ifaces.
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/sess.c

@@ -76,6 +76,7 @@ int cifs_try_adding_channels(struct cifs_ses *ses)
 	int left = ses->chan_max - ses->chan_count;
 	int i = 0;
 	int rc = 0;
+	int tries = 0;
 
 	if (left <= 0) {
 		cifs_dbg(FYI,
@@ -89,29 +90,40 @@ int cifs_try_adding_channels(struct cifs_ses *ses)
 		return 0;
 	}
 
-	/* ifaces are sorted by speed, try them in order */
-	for (i = 0; left > 0 && i < ses->iface_count; i++) {
+	/*
+	 * Keep connecting to same, fastest, iface for all channels as
+	 * long as its RSS. Try next fastest one if not RSS or channel
+	 * creation fails.
+	 */
+	while (left > 0) {
 		struct cifs_server_iface *iface;
 
+		tries++;
+		if (tries > 3*ses->chan_max) {
+			cifs_dbg(FYI, "too many attempt at opening channels (%d channels left to open)\n",
+				 left);
+			break;
+		}
+
 		iface = &ses->iface_list[i];
-		if (is_ses_using_iface(ses, iface) && !iface->rss_capable)
+		if (is_ses_using_iface(ses, iface) && !iface->rss_capable) {
+			i = (i+1) % ses->iface_count;
 			continue;
+		}
 
 		rc = cifs_ses_add_channel(ses, iface);
 		if (rc) {
-			cifs_dbg(FYI, "failed to open extra channel\n");
+			cifs_dbg(FYI, "failed to open extra channel on iface#%d rc=%d\n",
+				 i, rc);
+			i = (i+1) % ses->iface_count;
 			continue;
 		}
 
-		cifs_dbg(FYI, "successfully opened new channel\n");
+		cifs_dbg(FYI, "successfully opened new channel on iface#%d\n",
+			 i);
 		left--;
 	}
 
-	/*
-	 * TODO: if we still have channels left to open try to connect
-	 * to same RSS-capable iface multiple times
-	 */
-
 	return ses->chan_count - old_chan_count;
 }