cifs: avoid parallel session setups on same channel

After allowing channels to reconnect in parallel, it now
becomes important to take care that multiple processes do not
call negotiate/session setup in parallel on the same channel.

This change avoids that by marking a channel as "in_reconnect".
During session setup if the channel in question has this flag
set, we return immediately.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifs_debug.c

@@ -419,6 +419,8 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 			spin_lock(&ses->chan_lock);
 			if (CIFS_CHAN_NEEDS_RECONNECT(ses, 0))
 				seq_puts(m, "\tPrimary channel: DISCONNECTED ");
+			if (CIFS_CHAN_IN_RECONNECT(ses, 0))
+				seq_puts(m, "\t[RECONNECTING] ");
 
 			if (ses->chan_count > 1) {
 				seq_printf(m, "\n\n\tExtra Channels: %zu ",
@@ -427,6 +429,8 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 					cifs_dump_channel(m, j, &ses->chans[j]);
 					if (CIFS_CHAN_NEEDS_RECONNECT(ses, j))
 						seq_puts(m, "\tDISCONNECTED ");
+					if (CIFS_CHAN_IN_RECONNECT(ses, j))
+						seq_puts(m, "\t[RECONNECTING] ");
 				}
 			}
 			spin_unlock(&ses->chan_lock);

fs/cifs/cifsglob.h

@@ -922,6 +922,7 @@ struct cifs_server_iface {
 };
 
 struct cifs_chan {
+	unsigned int in_reconnect : 1; /* if session setup in progress for this channel */
 	struct TCP_Server_Info *server;
 	__u8 signkey[SMB3_SIGN_KEY_SIZE];
 };
@@ -984,12 +985,16 @@ struct cifs_ses {
 #define CIFS_MAX_CHANNELS 16
 #define CIFS_ALL_CHANNELS_SET(ses)	\
 	((1UL << (ses)->chan_count) - 1)
+#define CIFS_ALL_CHANS_GOOD(ses)		\
+	(!(ses)->chans_need_reconnect)
 #define CIFS_ALL_CHANS_NEED_RECONNECT(ses)	\
 	((ses)->chans_need_reconnect == CIFS_ALL_CHANNELS_SET(ses))
 #define CIFS_SET_ALL_CHANS_NEED_RECONNECT(ses)	\
 	((ses)->chans_need_reconnect = CIFS_ALL_CHANNELS_SET(ses))
 #define CIFS_CHAN_NEEDS_RECONNECT(ses, index)	\
 	test_bit((index), &(ses)->chans_need_reconnect)
+#define CIFS_CHAN_IN_RECONNECT(ses, index)	\
+	((ses)->chans[(index)].in_reconnect)
 
 	struct cifs_chan chans[CIFS_MAX_CHANNELS];
 	size_t chan_count;

fs/cifs/cifsproto.h

@@ -619,6 +619,15 @@ unsigned int
 cifs_ses_get_chan_index(struct cifs_ses *ses,
 			struct TCP_Server_Info *server);
 void
+cifs_chan_set_in_reconnect(struct cifs_ses *ses,
+			     struct TCP_Server_Info *server);
+void
+cifs_chan_clear_in_reconnect(struct cifs_ses *ses,
+			       struct TCP_Server_Info *server);
+bool
+cifs_chan_in_reconnect(struct cifs_ses *ses,
+			  struct TCP_Server_Info *server);
+void
 cifs_chan_set_need_reconnect(struct cifs_ses *ses,
 			     struct TCP_Server_Info *server);
 void

fs/cifs/connect.c

@@ -3995,17 +3995,27 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 	int rc = -ENOSYS;
 	bool is_binding = false;
 
-	/* only send once per connect */
-	spin_lock(&ses->chan_lock);
-	is_binding = !CIFS_ALL_CHANS_NEED_RECONNECT(ses);
-	spin_unlock(&ses->chan_lock);
 
 	spin_lock(&cifs_tcp_ses_lock);
-	if (ses->ses_status == SES_EXITING) {
+	if (ses->ses_status != SES_GOOD &&
+	    ses->ses_status != SES_NEW &&
+	    ses->ses_status != SES_NEED_RECON) {
 		spin_unlock(&cifs_tcp_ses_lock);
 		return 0;
 	}
 
+	/* only send once per connect */
+	spin_lock(&ses->chan_lock);
+	if (CIFS_ALL_CHANS_GOOD(ses) ||
+	    cifs_chan_in_reconnect(ses, server)) {
+		spin_unlock(&ses->chan_lock);
+		spin_unlock(&cifs_tcp_ses_lock);
+		return 0;
+	}
+	is_binding = !CIFS_ALL_CHANS_NEED_RECONNECT(ses);
+	cifs_chan_set_in_reconnect(ses, server);
+	spin_unlock(&ses->chan_lock);
+
 	if (!is_binding)
 		ses->ses_status = SES_IN_SETUP;
 	spin_unlock(&cifs_tcp_ses_lock);
@@ -4035,16 +4045,19 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 		spin_lock(&cifs_tcp_ses_lock);
 		if (ses->ses_status == SES_IN_SETUP)
 			ses->ses_status = SES_NEED_RECON;
+		spin_lock(&ses->chan_lock);
+		cifs_chan_clear_in_reconnect(ses, server);
+		spin_unlock(&ses->chan_lock);
 		spin_unlock(&cifs_tcp_ses_lock);
 	} else {
 		spin_lock(&cifs_tcp_ses_lock);
 		if (ses->ses_status == SES_IN_SETUP)
 			ses->ses_status = SES_GOOD;
-		spin_unlock(&cifs_tcp_ses_lock);
-
 		spin_lock(&ses->chan_lock);
+		cifs_chan_clear_in_reconnect(ses, server);
 		cifs_chan_clear_need_reconnect(ses, server);
 		spin_unlock(&ses->chan_lock);
+		spin_unlock(&cifs_tcp_ses_lock);
 	}
 
 	return rc;

fs/cifs/sess.c

@@ -85,6 +85,33 @@ cifs_ses_get_chan_index(struct cifs_ses *ses,
 	return 0;
 }
 
+void
+cifs_chan_set_in_reconnect(struct cifs_ses *ses,
+			     struct TCP_Server_Info *server)
+{
+	unsigned int chan_index = cifs_ses_get_chan_index(ses, server);
+
+	ses->chans[chan_index].in_reconnect = true;
+}
+
+void
+cifs_chan_clear_in_reconnect(struct cifs_ses *ses,
+			     struct TCP_Server_Info *server)
+{
+	unsigned int chan_index = cifs_ses_get_chan_index(ses, server);
+
+	ses->chans[chan_index].in_reconnect = false;
+}
+
+bool
+cifs_chan_in_reconnect(struct cifs_ses *ses,
+			  struct TCP_Server_Info *server)
+{
+	unsigned int chan_index = cifs_ses_get_chan_index(ses, server);
+
+	return CIFS_CHAN_IN_RECONNECT(ses, chan_index);
+}
+
 void
 cifs_chan_set_need_reconnect(struct cifs_ses *ses,
 			     struct TCP_Server_Info *server)