Hi Andrii,

I love your patch! Yet something to improve:

[auto build test ERROR on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Andrii-Nakryiko/BPF-XDP-link/20200714-120909
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: x86_64-defconfig (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 02946de3802d3bc65bc9f2eb9b8d4969b5a7add8)
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
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> net/core/dev.c:8717:18: error: field has incomplete type 'struct bpf_link'
           struct bpf_link link;
                           ^
   include/net/netns/bpf.h:15:9: note: forward declaration of 'struct bpf_link'
           struct bpf_link *links[MAX_NETNS_BPF_ATTACH_TYPE];
                  ^
>> net/core/dev.c:8992:34: error: variable has incomplete type 'const struct bpf_link_ops'
   static const struct bpf_link_ops bpf_xdp_link_lops = {
                                    ^
   net/core/dev.c:8992:21: note: forward declaration of 'struct bpf_link_ops'
   static const struct bpf_link_ops bpf_xdp_link_lops = {
                       ^
>> net/core/dev.c:9000:25: error: variable has incomplete type 'struct bpf_link_primer'
           struct bpf_link_primer link_primer;
                                  ^
   net/core/dev.c:9000:9: note: forward declaration of 'struct bpf_link_primer'
           struct bpf_link_primer link_primer;
                  ^
>> net/core/dev.c:9015:2: error: implicit declaration of function 'bpf_link_init' [-Werror,-Wimplicit-function-declaration]
           bpf_link_init(&link->link, BPF_LINK_TYPE_XDP, &bpf_xdp_link_lops, prog);
           ^
   net/core/dev.c:9015:2: note: did you mean 'bio_list_init'?
   include/linux/bio.h:575:20: note: 'bio_list_init' declared here
   static inline void bio_list_init(struct bio_list *bl)
                      ^
>> net/core/dev.c:9019:8: error: implicit declaration of function 'bpf_link_prime' [-Werror,-Wimplicit-function-declaration]
           err = bpf_link_prime(&link->link, &link_primer);
                 ^
   net/core/dev.c:9019:8: note: did you mean 'bpf_link_init'?
   net/core/dev.c:9015:2: note: 'bpf_link_init' declared here
           bpf_link_init(&link->link, BPF_LINK_TYPE_XDP, &bpf_xdp_link_lops, prog);
           ^
>> net/core/dev.c:9030:3: error: implicit declaration of function 'bpf_link_cleanup' [-Werror,-Wimplicit-function-declaration]
                   bpf_link_cleanup(&link_primer);
                   ^
   net/core/dev.c:9030:3: note: did you mean 'tcf_idr_cleanup'?
   include/net/act_api.h:171:6: note: 'tcf_idr_cleanup' declared here
   void tcf_idr_cleanup(struct tc_action_net *tn, u32 index);
        ^
>> net/core/dev.c:9034:7: error: implicit declaration of function 'bpf_link_settle' [-Werror,-Wimplicit-function-declaration]
           fd = bpf_link_settle(&link_primer);
                ^
   7 errors generated.

vim +8717 net/core/dev.c

  8715	
  8716	struct bpf_xdp_link {
> 8717		struct bpf_link link;
  8718		struct net_device *dev; /* protected by rtnl_lock, no refcnt held */
  8719		int flags;
  8720	};
  8721	

---
0-DAY CI Kernel Test Service, Intel Corporation
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