From: Shyam Prasad N <sprasad@microsoft.com>
Date: Mon, 19 Jul 2021 11:26:24 +0000
Subject: [PATCH] cifs: connect individual channel servers to primary channel
 server
Git-commit: 0f2b305af944973d6fa4acdb97151efe5b64aa55
Patch-mainline: v5.16-rc1
References: bsc#1192606

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>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
---
 fs/cifs/cifs_debug.c |    3 ++-
 fs/cifs/cifsglob.h   |    9 +++++++++
 fs/cifs/cifsproto.h  |    4 +++-
 fs/cifs/connect.c    |   24 ++++++++++++++++++++----
 fs/cifs/sess.c       |    6 +-----
 fs/cifs/smb2pdu.c    |    2 +-
 6 files changed, 36 insertions(+), 12 deletions(-)

--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -271,7 +271,8 @@ static int cifs_debug_data_proc_show(str
 	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++;
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -690,6 +690,15 @@ struct TCP_Server_Info {
 	 */
 	int nr_targets;
 	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;
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -254,7 +254,9 @@ extern void cifs_add_pending_open_locked
 					 struct tcon_link *tlink,
 					 struct cifs_pending_open *open);
 extern void cifs_del_pending_open(struct cifs_pending_open *open);
-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);
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -173,6 +173,7 @@ static void cifs_mark_tcp_ses_conns_for_
 	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_
 	 * 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_con
 		 * 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_I
 	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_I
 }
 
 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;
@@ -1437,6 +1447,10 @@ cifs_get_tcp_session(struct smb3_fs_cont
 	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);
@@ -1558,6 +1572,8 @@ out_err_crypto_release:
 
 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);
@@ -2957,7 +2973,7 @@ static int mount_get_conns(struct mount_
 	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;
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -258,7 +258,7 @@ cifs_ses_add_channel(struct cifs_sb_info
 	       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
 	}
 	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
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -257,7 +257,7 @@ smb2_reconnect(__le16 smb2_command, stru
 	/*
 	 * 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);
 	}