cifs: Identify a connection by a conn_id.

Introduced a new field conn_id in TCP_Server_Info structure.
This is a non-persistent unique identifier maintained by the client
for a connection to a file server. For this, a global counter named
tcpSesNextId is maintained. On allocating a new TCP_Server_Info,
this counter is incremented and assigned.

Changed the dynamic tracepoints related to reconnects and
crediting to be more informative (with conn_id printed).
Debugging a crediting issue helped me understand the
important things to print here.

Always call dynamic tracepoints outside the scope of spinlocks.
To do this, copy out the credits and in_flight fields of the
server struct before dropping the lock.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsfs.c

@@ -1525,6 +1525,7 @@ init_cifs(void)
  */
 	atomic_set(&sesInfoAllocCount, 0);
 	atomic_set(&tconInfoAllocCount, 0);
+	atomic_set(&tcpSesNextId, 0);
 	atomic_set(&tcpSesAllocCount, 0);
 	atomic_set(&tcpSesReconnectCount, 0);
 	atomic_set(&tconInfoReconnectCount, 0);

fs/cifs/cifsglob.h

@@ -577,6 +577,7 @@ inc_rfc1001_len(void *buf, int count)
 struct TCP_Server_Info {
 	struct list_head tcp_ses_list;
 	struct list_head smb_ses_list;
+	__u64 conn_id; /* connection identifier (useful for debugging) */
 	int srv_count; /* reference counter */
 	/* 15 character server name + 0x20 16th byte indicating type = srv */
 	char server_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
@@ -1846,6 +1847,7 @@ GLOBAL_EXTERN spinlock_t GlobalMid_Lock;  /* protects above & list operations */
  */
 GLOBAL_EXTERN atomic_t sesInfoAllocCount;
 GLOBAL_EXTERN atomic_t tconInfoAllocCount;
+GLOBAL_EXTERN atomic_t tcpSesNextId;
 GLOBAL_EXTERN atomic_t tcpSesAllocCount;
 GLOBAL_EXTERN atomic_t tcpSesReconnectCount;
 GLOBAL_EXTERN atomic_t tconInfoReconnectCount;

fs/cifs/connect.c

@@ -242,7 +242,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 	server->max_read = 0;
 
 	cifs_dbg(FYI, "Mark tcp session as need reconnect\n");
-	trace_smb3_reconnect(server->CurrentMid, server->hostname);
+	trace_smb3_reconnect(server->CurrentMid, server->conn_id, server->hostname);
 
 	/* before reconnecting the tcp session, mark the smb session (uid)
 		and the tid bad so they are not used until reconnected */
@@ -846,7 +846,7 @@ static void
 smb2_add_credits_from_hdr(char *buffer, struct TCP_Server_Info *server)
 {
 	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buffer;
-	int scredits = server->credits;
+	int scredits, in_flight;
 
 	/*
 	 * SMB1 does not use credits.
@@ -857,12 +857,14 @@ smb2_add_credits_from_hdr(char *buffer, struct TCP_Server_Info *server)
 	if (shdr->CreditRequest) {
 		spin_lock(&server->req_lock);
 		server->credits += le16_to_cpu(shdr->CreditRequest);
+		scredits = server->credits;
+		in_flight = server->in_flight;
 		spin_unlock(&server->req_lock);
 		wake_up(&server->request_q);
 
 		trace_smb3_add_credits(server->CurrentMid,
-				server->hostname, scredits,
-				le16_to_cpu(shdr->CreditRequest));
+				server->conn_id, server->hostname, scredits,
+				le16_to_cpu(shdr->CreditRequest), in_flight);
 		cifs_server_dbg(FYI, "%s: added %u credits total=%d\n",
 				__func__, le16_to_cpu(shdr->CreditRequest),
 				scredits);
@@ -1317,6 +1319,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 		goto out_err_crypto_release;
 	}
 
+	tcp_ses->conn_id = atomic_inc_return(&tcpSesNextId);
 	tcp_ses->noblockcnt = ctx->rootfs;
 	tcp_ses->noblocksnd = ctx->noblocksnd || ctx->rootfs;
 	tcp_ses->noautotune = ctx->noautotune;

fs/cifs/smb2ops.c

@@ -63,17 +63,19 @@ smb2_add_credits(struct TCP_Server_Info *server,
 		 const struct cifs_credits *credits, const int optype)
 {
 	int *val, rc = -1;
+	int scredits, in_flight;
 	unsigned int add = credits->value;
 	unsigned int instance = credits->instance;
 	bool reconnect_detected = false;
+	bool reconnect_with_invalid_credits = false;
 
 	spin_lock(&server->req_lock);
 	val = server->ops->get_credits_field(server, optype);
 
 	/* eg found case where write overlapping reconnect messed up credits */
 	if (((optype & CIFS_OP_MASK) == CIFS_NEG_OP) && (*val != 0))
-		trace_smb3_reconnect_with_invalid_credits(server->CurrentMid,
-			server->hostname, *val, add);
+		reconnect_with_invalid_credits = true;
+
 	if ((instance == 0) || (instance == server->reconnect_instance))
 		*val += add;
 	else
@@ -99,14 +101,26 @@ smb2_add_credits(struct TCP_Server_Info *server,
 			server->oplock_credits++;
 		}
 	}
+	scredits = *val;
+	in_flight = server->in_flight;
 	spin_unlock(&server->req_lock);
 	wake_up(&server->request_q);
 
 	if (reconnect_detected) {
+		trace_smb3_reconnect_detected(server->CurrentMid,
+			server->conn_id, server->hostname, scredits, add, in_flight);
+
 		cifs_dbg(FYI, "trying to put %d credits from the old server instance %d\n",
 			 add, instance);
 	}
 
+	if (reconnect_with_invalid_credits) {
+		trace_smb3_reconnect_with_invalid_credits(server->CurrentMid,
+			server->conn_id, server->hostname, scredits, add, in_flight);
+		cifs_dbg(FYI, "Negotiate operation when server credits is non-zero. Optype: %d, server credits: %d, credits added: %d\n",
+			 optype, scredits, add);
+	}
+
 	if (server->tcpStatus == CifsNeedReconnect
 	    || server->tcpStatus == CifsExiting)
 		return;
@@ -125,23 +139,30 @@ smb2_add_credits(struct TCP_Server_Info *server,
 		cifs_dbg(FYI, "disabling oplocks\n");
 		break;
 	default:
-		trace_smb3_add_credits(server->CurrentMid,
-			server->hostname, rc, add);
-		cifs_dbg(FYI, "%s: added %u credits total=%d\n", __func__, add, rc);
+		/* change_conf rebalanced credits for different types */
+		break;
 	}
+
+	trace_smb3_add_credits(server->CurrentMid,
+			server->conn_id, server->hostname, scredits, add, in_flight);
+	cifs_dbg(FYI, "%s: added %u credits total=%d\n", __func__, add, scredits);
 }
 
 static void
 smb2_set_credits(struct TCP_Server_Info *server, const int val)
 {
+	int scredits, in_flight;
+
 	spin_lock(&server->req_lock);
 	server->credits = val;
 	if (val == 1)
 		server->reconnect_instance++;
+	scredits = server->credits;
+	in_flight = server->in_flight;
 	spin_unlock(&server->req_lock);
 
 	trace_smb3_set_credits(server->CurrentMid,
-			server->hostname, val, val);
+			server->conn_id, server->hostname, scredits, val, in_flight);
 	cifs_dbg(FYI, "%s: set %u credits\n", __func__, val);
 
 	/* don't log while holding the lock */
@@ -173,7 +194,7 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
 		      unsigned int *num, struct cifs_credits *credits)
 {
 	int rc = 0;
-	unsigned int scredits;
+	unsigned int scredits, in_flight;
 
 	spin_lock(&server->req_lock);
 	while (1) {
@@ -210,17 +231,18 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
 				DIV_ROUND_UP(*num, SMB2_MAX_BUFFER_SIZE);
 			credits->instance = server->reconnect_instance;
 			server->credits -= credits->value;
-			scredits = server->credits;
 			server->in_flight++;
 			if (server->in_flight > server->max_in_flight)
 				server->max_in_flight = server->in_flight;
 			break;
 		}
 	}
+	scredits = server->credits;
+	in_flight = server->in_flight;
 	spin_unlock(&server->req_lock);
 
 	trace_smb3_add_credits(server->CurrentMid,
-			server->hostname, scredits, -(credits->value));
+			server->conn_id, server->hostname, scredits, -(credits->value), in_flight);
 	cifs_dbg(FYI, "%s: removed %u credits total=%d\n",
 			__func__, credits->value, scredits);
 
@@ -233,14 +255,14 @@ smb2_adjust_credits(struct TCP_Server_Info *server,
 		    const unsigned int payload_size)
 {
 	int new_val = DIV_ROUND_UP(payload_size, SMB2_MAX_BUFFER_SIZE);
-	int scredits;
+	int scredits, in_flight;
 
 	if (!credits->value || credits->value == new_val)
 		return 0;
 
 	if (credits->value < new_val) {
 		trace_smb3_too_many_credits(server->CurrentMid,
-				server->hostname, 0, credits->value - new_val);
+				server->conn_id, server->hostname, 0, credits->value - new_val, 0);
 		cifs_server_dbg(VFS, "request has less credits (%d) than required (%d)",
 				credits->value, new_val);
 
@@ -250,9 +272,13 @@ smb2_adjust_credits(struct TCP_Server_Info *server,
 	spin_lock(&server->req_lock);
 
 	if (server->reconnect_instance != credits->instance) {
+		scredits = server->credits;
+		in_flight = server->in_flight;
 		spin_unlock(&server->req_lock);
+
 		trace_smb3_reconnect_detected(server->CurrentMid,
-			server->hostname, 0, 0);
+			server->conn_id, server->hostname, scredits,
+			credits->value - new_val, in_flight);
 		cifs_server_dbg(VFS, "trying to return %d credits to old session\n",
 			 credits->value - new_val);
 		return -EAGAIN;
@@ -260,15 +286,18 @@ smb2_adjust_credits(struct TCP_Server_Info *server,
 
 	server->credits += credits->value - new_val;
 	scredits = server->credits;
+	in_flight = server->in_flight;
 	spin_unlock(&server->req_lock);
 	wake_up(&server->request_q);
-	credits->value = new_val;
 
 	trace_smb3_add_credits(server->CurrentMid,
-			server->hostname, scredits, credits->value - new_val);
+			server->conn_id, server->hostname, scredits,
+			credits->value - new_val, in_flight);
 	cifs_dbg(FYI, "%s: adjust added %u credits total=%d\n",
 			__func__, credits->value - new_val, scredits);
 
+	credits->value = new_val;
+
 	return 0;
 }
 
@@ -2371,7 +2400,7 @@ static bool
 smb2_is_status_pending(char *buf, struct TCP_Server_Info *server)
 {
 	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buf;
-	int scredits;
+	int scredits, in_flight;
 
 	if (shdr->Status != STATUS_PENDING)
 		return false;
@@ -2380,11 +2409,13 @@ smb2_is_status_pending(char *buf, struct TCP_Server_Info *server)
 		spin_lock(&server->req_lock);
 		server->credits += le16_to_cpu(shdr->CreditRequest);
 		scredits = server->credits;
+		in_flight = server->in_flight;
 		spin_unlock(&server->req_lock);
 		wake_up(&server->request_q);
 
 		trace_smb3_add_credits(server->CurrentMid,
-				server->hostname, scredits, le16_to_cpu(shdr->CreditRequest));
+				server->conn_id, server->hostname, scredits,
+				le16_to_cpu(shdr->CreditRequest), in_flight);
 		cifs_dbg(FYI, "%s: status pending add %u credits total=%d\n",
 				__func__, le16_to_cpu(shdr->CreditRequest), scredits);
 	}

fs/cifs/trace.h

@@ -851,17 +851,21 @@ DEFINE_SMB3_LEASE_ERR_EVENT(lease_err);
 
 DECLARE_EVENT_CLASS(smb3_reconnect_class,
 	TP_PROTO(__u64	currmid,
+		__u64 conn_id,
 		char *hostname),
-	TP_ARGS(currmid, hostname),
+	TP_ARGS(currmid, conn_id, hostname),
 	TP_STRUCT__entry(
 		__field(__u64, currmid)
+		__field(__u64, conn_id)
 		__field(char *, hostname)
 	),
 	TP_fast_assign(
 		__entry->currmid = currmid;
+		__entry->conn_id = conn_id;
 		__entry->hostname = hostname;
 	),
-	TP_printk("server=%s current_mid=0x%llx",
+	TP_printk("conn_id=0x%llx server=%s current_mid=%llu",
+		__entry->conn_id,
 		__entry->hostname,
 		__entry->currmid)
 )
@@ -869,44 +873,56 @@ DECLARE_EVENT_CLASS(smb3_reconnect_class,
 #define DEFINE_SMB3_RECONNECT_EVENT(name)        \
 DEFINE_EVENT(smb3_reconnect_class, smb3_##name,  \
 	TP_PROTO(__u64	currmid,		\
-		char *hostname),		\
-	TP_ARGS(currmid, hostname))
+		__u64 conn_id,			\
+		char *hostname),				\
+	TP_ARGS(currmid, conn_id, hostname))
 
 DEFINE_SMB3_RECONNECT_EVENT(reconnect);
 DEFINE_SMB3_RECONNECT_EVENT(partial_send_reconnect);
 
 DECLARE_EVENT_CLASS(smb3_credit_class,
 	TP_PROTO(__u64	currmid,
+		__u64 conn_id,
 		char *hostname,
 		int credits,
-		int credits_to_add),
-	TP_ARGS(currmid, hostname, credits, credits_to_add),
+		int credits_to_add,
+		int in_flight),
+	TP_ARGS(currmid, conn_id, hostname, credits, credits_to_add, in_flight),
 	TP_STRUCT__entry(
 		__field(__u64, currmid)
+		__field(__u64, conn_id)
 		__field(char *, hostname)
 		__field(int, credits)
 		__field(int, credits_to_add)
+		__field(int, in_flight)
 	),
 	TP_fast_assign(
 		__entry->currmid = currmid;
+		__entry->conn_id = conn_id;
 		__entry->hostname = hostname;
 		__entry->credits = credits;
 		__entry->credits_to_add = credits_to_add;
+		__entry->in_flight = in_flight;
 	),
-	TP_printk("server=%s current_mid=0x%llx credits=%d credits_to_add=%d",
+	TP_printk("conn_id=0x%llx server=%s current_mid=%llu "
+			"credits=%d credit_change=%d in_flight=%d",
+		__entry->conn_id,
 		__entry->hostname,
 		__entry->currmid,
 		__entry->credits,
-		__entry->credits_to_add)
+		__entry->credits_to_add,
+		__entry->in_flight)
 )
 
 #define DEFINE_SMB3_CREDIT_EVENT(name)        \
 DEFINE_EVENT(smb3_credit_class, smb3_##name,  \
 	TP_PROTO(__u64	currmid,		\
+		__u64 conn_id,			\
 		char *hostname,			\
 		int  credits,			\
-		int  credits_to_add),		\
-	TP_ARGS(currmid, hostname, credits, credits_to_add))
+		int  credits_to_add,	\
+		int in_flight),			\
+	TP_ARGS(currmid, conn_id, hostname, credits, credits_to_add, in_flight))
 
 DEFINE_SMB3_CREDIT_EVENT(reconnect_with_invalid_credits);
 DEFINE_SMB3_CREDIT_EVENT(reconnect_detected);

fs/cifs/transport.c

@@ -445,7 +445,7 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
 		 */
 		server->tcpStatus = CifsNeedReconnect;
 		trace_smb3_partial_send_reconnect(server->CurrentMid,
-						  server->hostname);
+						  server->conn_id, server->hostname);
 	}
 smbd_done:
 	if (rc < 0 && rc != -EINTR)
@@ -527,7 +527,7 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 	int *credits;
 	int optype;
 	long int t;
-	int scredits = server->credits;
+	int scredits, in_flight;
 
 	if (timeout < 0)
 		t = MAX_JIFFY_OFFSET;
@@ -551,22 +551,38 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 			server->max_in_flight = server->in_flight;
 		*credits -= 1;
 		*instance = server->reconnect_instance;
+		scredits = *credits;
+		in_flight = server->in_flight;
 		spin_unlock(&server->req_lock);
+
+		trace_smb3_add_credits(server->CurrentMid,
+				server->conn_id, server->hostname, scredits, -1, in_flight);
+		cifs_dbg(FYI, "%s: remove %u credits total=%d\n",
+				__func__, 1, scredits);
+
 		return 0;
 	}
 
 	while (1) {
 		if (*credits < num_credits) {
+			scredits = *credits;
 			spin_unlock(&server->req_lock);
+
 			cifs_num_waiters_inc(server);
 			rc = wait_event_killable_timeout(server->request_q,
 				has_credits(server, credits, num_credits), t);
 			cifs_num_waiters_dec(server);
 			if (!rc) {
+				spin_lock(&server->req_lock);
+				scredits = *credits;
+				in_flight = server->in_flight;
+				spin_unlock(&server->req_lock);
+
 				trace_smb3_credit_timeout(server->CurrentMid,
-					server->hostname, num_credits, 0);
+						server->conn_id, server->hostname, scredits,
+						num_credits, in_flight);
 				cifs_server_dbg(VFS, "wait timed out after %d ms\n",
-					 timeout);
+						timeout);
 				return -EBUSY;
 			}
 			if (rc == -ERESTARTSYS)
@@ -595,6 +611,7 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 			    server->in_flight > 2 * MAX_COMPOUND &&
 			    *credits <= MAX_COMPOUND) {
 				spin_unlock(&server->req_lock);
+
 				cifs_num_waiters_inc(server);
 				rc = wait_event_killable_timeout(
 					server->request_q,
@@ -603,12 +620,17 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 					t);
 				cifs_num_waiters_dec(server);
 				if (!rc) {
+					spin_lock(&server->req_lock);
+					scredits = *credits;
+					in_flight = server->in_flight;
+					spin_unlock(&server->req_lock);
+
 					trace_smb3_credit_timeout(
-						server->CurrentMid,
-						server->hostname, num_credits,
-						0);
+							server->CurrentMid,
+							server->conn_id, server->hostname,
+							scredits, num_credits, in_flight);
 					cifs_server_dbg(VFS, "wait timed out after %d ms\n",
-						 timeout);
+							timeout);
 					return -EBUSY;
 				}
 				if (rc == -ERESTARTSYS)
@@ -625,16 +647,18 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 			/* update # of requests on the wire to server */
 			if ((flags & CIFS_TIMEOUT_MASK) != CIFS_BLOCKING_OP) {
 				*credits -= num_credits;
-				scredits = *credits;
 				server->in_flight += num_credits;
 				if (server->in_flight > server->max_in_flight)
 					server->max_in_flight = server->in_flight;
 				*instance = server->reconnect_instance;
 			}
+			scredits = *credits;
+			in_flight = server->in_flight;
 			spin_unlock(&server->req_lock);
 
 			trace_smb3_add_credits(server->CurrentMid,
-					server->hostname, scredits, -(num_credits));
+					server->conn_id, server->hostname, scredits,
+					-(num_credits), in_flight);
 			cifs_dbg(FYI, "%s: remove %u credits total=%d\n",
 					__func__, num_credits, scredits);
 			break;
@@ -656,13 +680,13 @@ wait_for_compound_request(struct TCP_Server_Info *server, int num,
 			  const int flags, unsigned int *instance)
 {
 	int *credits;
-	int scredits, sin_flight;
+	int scredits, in_flight;
 
 	credits = server->ops->get_credits_field(server, flags & CIFS_OP_MASK);
 
 	spin_lock(&server->req_lock);
 	scredits = *credits;
-	sin_flight = server->in_flight;
+	in_flight = server->in_flight;
 
 	if (*credits < num) {
 		/*
@@ -684,9 +708,10 @@ wait_for_compound_request(struct TCP_Server_Info *server, int num,
 		if (server->in_flight == 0) {
 			spin_unlock(&server->req_lock);
 			trace_smb3_insufficient_credits(server->CurrentMid,
-					server->hostname, scredits, sin_flight);
+					server->conn_id, server->hostname, scredits,
+					num, in_flight);
 			cifs_dbg(FYI, "%s: %d requests in flight, needed %d total=%d\n",
-					__func__, sin_flight, num, scredits);
+					__func__, in_flight, num, scredits);
 			return -EDEADLK;
 		}
 	}