add nfs v3 support to nfsdist.py (#2902)

add nfs v3 support to nfsdist.py

Co-authored-by: sabbene <sabbene@sabbene.nvidia.com>

tools/nfsdist.py

@@ -137,16 +137,21 @@
 # common file functions
 b.attach_kprobe(event="nfs_file_read", fn_name="trace_entry")
 b.attach_kprobe(event="nfs_file_write", fn_name="trace_entry")
-b.attach_kprobe(event="nfs4_file_open", fn_name="trace_entry")
 b.attach_kprobe(event="nfs_file_open", fn_name="trace_entry")
 b.attach_kprobe(event="nfs_getattr", fn_name="trace_entry")
 
 b.attach_kretprobe(event="nfs_file_read", fn_name="trace_read_return")
 b.attach_kretprobe(event="nfs_file_write", fn_name="trace_write_return")
-b.attach_kretprobe(event="nfs4_file_open", fn_name="trace_open_return")
 b.attach_kretprobe(event="nfs_file_open", fn_name="trace_open_return")
 b.attach_kretprobe(event="nfs_getattr", fn_name="trace_getattr_return")
 
+if BPF.get_kprobe_functions(b'nfs4_file_open'):
+    b.attach_kprobe(event="nfs4_file_open", fn_name="trace_entry")
+    b.attach_kretprobe(event="nfs4_file_open", fn_name="trace_open_return")
+else:
+    b.attach_kprobe(event="nfs_file_open", fn_name="trace_entry")
+    b.attach_kretprobe(event="nfs_file_open", fn_name="trace_open_return")
+
 print("Tracing NFS operation latency... Hit Ctrl-C to end.")
 
 # output