On Wed, 10 Feb 2016 16:55:14 +1100 Stephen Rothwell [off-list ref] wrote:

Hi Andrew,

After merging the akpm-current tree, today's linux-next build (x86_64
allmodconfig) failed like this:

In file included from arch/x86/include/asm/bug.h:35:0,
                 from include/linux/bug.h:4,
                 from include/linux/thread_info.h:11,
                 from arch/x86/include/asm/preempt.h:6,
                 from include/linux/preempt.h:59,
                 from include/linux/radix-tree.h:25,
                 from kernel/memremap.c:13:
kernel/memremap.c: In function 'devm_memremap_pages_release':
kernel/memremap.c:230:54: error: expected ')' before '__func__'
   dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
                                                      ^
include/asm-generic/bug.h:74:69: note: in definition of macro '__WARN_printf'
 #define __WARN_printf(arg...) warn_slowpath_fmt(__FILE__, __LINE__, arg)
                                                                     ^
include/linux/device.h:1312:2: note: in expansion of macro 'WARN'
  WARN(condition, "%s %s: " format,   \
  ^
kernel/memremap.c:230:3: note: in expansion of macro 'dev_WARN'
   dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
   ^
include/linux/device.h:1312:18: warning: format '%s' expects a matching 'char *' argument [-Wformat=]
  WARN(condition, "%s %s: " format,   \
                  ^
include/asm-generic/bug.h:74:69: note: in definition of macro '__WARN_printf'
 #define __WARN_printf(arg...) warn_slowpath_fmt(__FILE__, __LINE__, arg)
                                                                     ^
include/linux/device.h:1312:2: note: in expansion of macro 'WARN'
  WARN(condition, "%s %s: " format,   \
  ^
kernel/memremap.c:230:3: note: in expansion of macro 'dev_WARN'
   dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
   ^

Probably exposed by commit

  27ffb3827ac7 ("mm: CONFIG_NR_ZONES_EXTENDED")

originally caused by commit

  5c2c2587b132 ("mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup")

which was added in v4.5-rc1.

I added the below patch for today but then discovered the waiting patch
in the akpm tree ("kernel/memremap.c: add new arg to dev_WARN") which
should be sent to Linus ASAP (and should have appeared much earlier in
the series).

kernel-memremapc-add-new-arg-to-dev_warn.patch fixes ee49ac85bc24b946
("treewide: let dev_WARN() accept a condition") which is only in
linux-next?