Hi Andrew,

It's probably a bug fix that unveils the link errors.

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   e1e12812e428bcaf19e23f83e09f602d161b8005
commit: c429f45c501ac95383be9e37467d4e6ca08782c1 [4658/4676] daxext2-replace-the-xip-page-fault-handler-with-the-dax-page-fault-handler-fix-3
config: mips-allmodconfig (attached as .config)
reproduce:
  wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
  chmod +x ~/bin/make.cross
  git checkout c429f45c501ac95383be9e37467d4e6ca08782c1
  # save the attached .config to linux build tree
  make.cross ARCH=mips 

All error/warnings:

   fs/built-in.o: In function `dax_fault':
>> (.text+0x5dc6c): undefined reference to `copy_user_page'

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