afs: Trace the initiation and completion of client calls

Add tracepoints to trace the initiation and completion of client calls
within the kafs filesystem.

The afs_make_vl_call tracepoint watches calls to the volume location
database server.

The afs_make_fs_call tracepoint watches calls to the file server.

The afs_call_done tracepoint watches for call completion.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 767317b..aad1254 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -124,6 +124,7 @@ struct afs_call {
 
 struct afs_call_type {
 	const char *name;
+	unsigned int op; /* Really enum afs_fs_operation */
 
 	/* deliver request or reply data to an call
 	 * - returning an error will cause the call to be aborted