Hi Lorenz,

I love your patch! Yet something to improve:

[auto build test ERROR on bpf/master]

url:    https://github.com/0day-ci/linux/commits/Lorenz-Bauer/Expose-network-namespace-cookies-to-user-space/20210210-201857
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git master
config: microblaze-randconfig-r003-20210209 (attached as .config)
compiler: microblaze-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/ec096a87ec268b0634a140515fb54b21a2c67036
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Lorenz-Bauer/Expose-network-namespace-cookies-to-user-space/20210210-201857
        git checkout ec096a87ec268b0634a140515fb54b21a2c67036
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=microblaze 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All errors (new ones prefixed by >>):

   microblaze-linux-ld: fs/nsfs.o: in function `ns_ioctl':

quoted

(.text+0x1618): undefined reference to `__net_gen_cookie'

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org