smb3: add dynamic tracepoint for timeout waiting for credits

To help debug credit starvation problems where we timeout
waiting for server to grant the client credits.
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/trace.h

@@ -713,6 +713,7 @@ DEFINE_EVENT(smb3_credit_class, smb3_##name,  \
 	TP_ARGS(currmid, hostname, credits))
 
 DEFINE_SMB3_CREDIT_EVENT(reconnect_with_invalid_credits);
+DEFINE_SMB3_CREDIT_EVENT(credit_timeout);
 
 #endif /* _CIFS_TRACE_H */
 

fs/cifs/transport.c

@@ -527,6 +527,8 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 				has_credits(server, credits, num_credits), t);
 			cifs_num_waiters_dec(server);
 			if (!rc) {
+				trace_smb3_credit_timeout(server->CurrentMid,
+					server->hostname, num_credits);
 				cifs_dbg(VFS, "wait timed out after %d ms\n",
 					 timeout);
 				return -ENOTSUPP;
@@ -565,6 +567,9 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 					t);
 				cifs_num_waiters_dec(server);
 				if (!rc) {
+					trace_smb3_credit_timeout(
+						server->CurrentMid,
+						server->hostname, num_credits);
 					cifs_dbg(VFS, "wait timed out after %d ms\n",
 						 timeout);
 					return -ENOTSUPP;