cifs: connect individual channel servers to primary channel server

Today, we don't have any way to get the smb session for any
of the secondary channels. Introducing a pointer to the primary
server from server struct of any secondary channel. The value will
be NULL for the server of the primary channel. This will enable us
to get the smb session for any channel.

This will be needed for some of the changes that I'm planning
to make soon.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifs_debug.c

@@ -271,7 +271,8 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 	c = 0;
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(server, &cifs_tcp_ses_list, tcp_ses_list) {
-		if (server->is_channel)
+		/* channel info will be printed as a part of sessions below */
+		if (CIFS_SERVER_IS_CHAN(server))
 			continue;
 
 		c++;

fs/cifs/cifsglob.h

@@ -690,7 +690,15 @@ struct TCP_Server_Info {
 	 */
 	int nr_targets;
 	bool noblockcnt; /* use non-blocking connect() */
-	bool is_channel; /* if a session channel */
+
+	/*
+	 * If this is a session channel,
+	 * primary_server holds the ref-counted
+	 * pointer to primary channel connection for the session.
+	 */
+#define CIFS_SERVER_IS_CHAN(server)	(!!(server)->primary_server)
+	struct TCP_Server_Info *primary_server;
+
 #ifdef CONFIG_CIFS_SWN_UPCALL
 	bool use_swn_dstaddr;
 	struct sockaddr_storage swn_dstaddr;

fs/cifs/cifsproto.h

@@ -269,8 +269,9 @@ extern void cifs_close_all_deferred_files(struct cifs_tcon *cifs_tcon);
 
 extern void cifs_close_deferred_file_under_dentry(struct cifs_tcon *cifs_tcon,
 				const char *path);
-
-extern struct TCP_Server_Info *cifs_get_tcp_session(struct smb3_fs_context *ctx);
+extern struct TCP_Server_Info *
+cifs_get_tcp_session(struct smb3_fs_context *ctx,
+		     struct TCP_Server_Info *primary_server);
 extern void cifs_put_tcp_session(struct TCP_Server_Info *server,
 				 int from_reconnect);
 extern void cifs_put_tcon(struct cifs_tcon *tcon);

fs/cifs/connect.c

@@ -173,6 +173,7 @@ static void cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server
 	struct cifs_tcon *tcon;
 	struct mid_q_entry *mid, *nmid;
 	struct list_head retry_list;
+	struct TCP_Server_Info *pserver;
 
 	server->maxBuf = 0;
 	server->max_read = 0;
@@ -184,8 +185,12 @@ static void cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server
 	 * are not used until reconnected.
 	 */
 	cifs_dbg(FYI, "%s: marking sessions and tcons for reconnect\n", __func__);
+
+	/* If server is a channel, select the primary channel */
+	pserver = CIFS_SERVER_IS_CHAN(server) ? server->primary_server : server;
+
 	spin_lock(&cifs_tcp_ses_lock);
-	list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
+	list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
 		ses->need_reconnect = true;
 		list_for_each_entry(tcon, &ses->tcon_list, tcon_list)
 			tcon->need_reconnect = true;
@@ -1338,7 +1343,7 @@ cifs_find_tcp_session(struct smb3_fs_context *ctx)
 		 * Skip ses channels since they're only handled in lower layers
 		 * (e.g. cifs_send_recv).
 		 */
-		if (server->is_channel || !match_server(server, ctx))
+		if (CIFS_SERVER_IS_CHAN(server) || !match_server(server, ctx))
 			continue;
 
 		++server->srv_count;
@@ -1369,6 +1374,10 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 	list_del_init(&server->tcp_ses_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 
+	/* For secondary channels, we pick up ref-count on the primary server */
+	if (CIFS_SERVER_IS_CHAN(server))
+		cifs_put_tcp_session(server->primary_server, from_reconnect);
+
 	cancel_delayed_work_sync(&server->echo);
 	cancel_delayed_work_sync(&server->resolve);
 
@@ -1401,7 +1410,8 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 }
 
 struct TCP_Server_Info *
-cifs_get_tcp_session(struct smb3_fs_context *ctx)
+cifs_get_tcp_session(struct smb3_fs_context *ctx,
+		     struct TCP_Server_Info *primary_server)
 {
 	struct TCP_Server_Info *tcp_ses = NULL;
 	int rc;
@@ -1438,6 +1448,10 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 	tcp_ses->in_flight = 0;
 	tcp_ses->max_in_flight = 0;
 	tcp_ses->credits = 1;
+	if (primary_server) {
+		++primary_server->srv_count;
+		tcp_ses->primary_server = primary_server;
+	}
 	init_waitqueue_head(&tcp_ses->response_q);
 	init_waitqueue_head(&tcp_ses->request_q);
 	INIT_LIST_HEAD(&tcp_ses->pending_mid_q);
@@ -1559,6 +1573,8 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 
 out_err:
 	if (tcp_ses) {
+		if (CIFS_SERVER_IS_CHAN(tcp_ses))
+			cifs_put_tcp_session(tcp_ses->primary_server, false);
 		kfree(tcp_ses->hostname);
 		if (tcp_ses->ssocket)
 			sock_release(tcp_ses->ssocket);
@@ -2960,7 +2976,7 @@ static int mount_get_conns(struct mount_ctx *mnt_ctx)
 	xid = get_xid();
 
 	/* get a reference to a tcp session */
-	server = cifs_get_tcp_session(ctx);
+	server = cifs_get_tcp_session(ctx, NULL);
 	if (IS_ERR(server)) {
 		rc = PTR_ERR(server);
 		server = NULL;

fs/cifs/sess.c

@@ -258,7 +258,7 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 	       SMB2_CLIENT_GUID_SIZE);
 	ctx.use_client_guid = true;
 
-	chan_server = cifs_get_tcp_session(&ctx);
+	chan_server = cifs_get_tcp_session(&ctx, ses->server);
 
 	mutex_lock(&ses->session_mutex);
 	spin_lock(&ses->chan_lock);
@@ -272,10 +272,6 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 	}
 	spin_unlock(&ses->chan_lock);
 
-	spin_lock(&cifs_tcp_ses_lock);
-	chan->server->is_channel = true;
-	spin_unlock(&cifs_tcp_ses_lock);
-
 	/*
 	 * We need to allocate the server crypto now as we will need
 	 * to sign packets before we generate the channel signing key

fs/cifs/smb2pdu.c

@@ -257,7 +257,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
 	/*
 	 * If we are reconnecting an extra channel, bind
 	 */
-	if (server->is_channel) {
+	if (CIFS_SERVER_IS_CHAN(server)) {
 		ses->binding = true;
 		ses->binding_chan = cifs_ses_find_chan(ses, server);
 	}