Hi all,

After merging the block tree, today's linux-next build (x86_64
allmodconfig) produced this warning:

In file included from include/trace/events/iocost.h:8,
                 from <command-line>:
include/trace/events/iocost.h:12:57: warning: 'struct ioc_now' declared inside parameter list will not be visible outside of this definition or declaration
  TP_PROTO(struct ioc_gq *iocg, const char *path, struct ioc_now *now,
                                                         ^~~~~~~
include/linux/tracepoint.h:233:34: note: in definition of macro '__DECLARE_TRACE'
  static inline void trace_##name(proto)    \
                                  ^~~~~
include/linux/tracepoint.h:396:24: note: in expansion of macro 'PARAMS'
  __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),  \
                        ^~~~~~
include/linux/tracepoint.h:532:2: note: in expansion of macro 'DECLARE_TRACE'
  DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
  ^~~~~~~~~~~~~
include/linux/tracepoint.h:532:22: note: in expansion of macro 'PARAMS'
  DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
                      ^~~~~~
include/trace/events/iocost.h:10:1: note: in expansion of macro 'TRACE_EVENT'
 TRACE_EVENT(iocost_iocg_activate,
 ^~~~~~~~~~~
include/trace/events/iocost.h:12:2: note: in expansion of macro 'TP_PROTO'
  TP_PROTO(struct ioc_gq *iocg, const char *path, struct ioc_now *now,
  ^~~~~~~~
include/trace/events/iocost.h:12:18: warning: 'struct ioc_gq' declared inside parameter list will not be visible outside of this definition or declaration
  TP_PROTO(struct ioc_gq *iocg, const char *path, struct ioc_now *now,
                  ^~~~~~
include/linux/tracepoint.h:233:34: note: in definition of macro '__DECLARE_TRACE'
  static inline void trace_##name(proto)    \
                                  ^~~~~
include/linux/tracepoint.h:396:24: note: in expansion of macro 'PARAMS'
  __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),  \
                        ^~~~~~
include/linux/tracepoint.h:532:2: note: in expansion of macro 'DECLARE_TRACE'
  DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
  ^~~~~~~~~~~~~
include/linux/tracepoint.h:532:22: note: in expansion of macro 'PARAMS'
  DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
                      ^~~~~~
include/trace/events/iocost.h:10:1: note: in expansion of macro 'TRACE_EVENT'
 TRACE_EVENT(iocost_iocg_activate,
 ^~~~~~~~~~~
include/trace/events/iocost.h:12:2: note: in expansion of macro 'TP_PROTO'
  TP_PROTO(struct ioc_gq *iocg, const char *path, struct ioc_now *now,
  ^~~~~~~~

(and many more)

Introduced by commit

  7caa47151ab2 ("blkcg: implement blk-iocost")

To get these warnings you need to build with CONFIG_HEADER_TEST and
CONFIG_KERNEL_HEADER_TEST (and maybe CONFIG_UAPI_HEADER_TEST).
allmodconfig does that.

-- 
Cheers,
Stephen Rothwell