Hi Andrii,

I love your patch! Yet something to improve:

[auto build test ERROR on bpf-next/master]
[cannot apply to bpf/master cgroup/for-next v5.6-rc6 next-20200320]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Andrii-Nakryiko/Add-support-for-cgroup-bpf_link/20200321-045848
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: mips-64r6el_defconfig (attached as .config)
compiler: mips64el-linux-gcc (GCC) 5.5.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=5.5.0 make.cross ARCH=mips 

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

All errors (new ones prefixed by >>):

   In file included from include/linux/kernel.h:11:0,
                    from include/linux/list.h:9,
                    from include/linux/timer.h:5,
                    from include/linux/workqueue.h:9,
                    from include/linux/bpf.h:9,
                    from kernel/bpf/syscall.c:4:
   kernel/bpf/syscall.c: In function 'link_update':
   include/linux/kernel.h:994:51: error: dereferencing pointer to incomplete type 'struct bpf_cgroup_link'
     BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
                                                      ^
   include/linux/compiler.h:330:9: note: in definition of macro '__compiletime_assert'
      if (!(condition))     \
            ^
   include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
     ^
   include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                        ^
   include/linux/kernel.h:994:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
     BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
     ^
   include/linux/kernel.h:994:20: note: in expansion of macro '__same_type'
     BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
                       ^
   kernel/bpf/syscall.c:3612:13: note: in expansion of macro 'container_of'
      cg_link = container_of(link, struct bpf_cgroup_link, link);
                ^
   In file included from <command-line>:0:0:
>> kernel/bpf/syscall.c:3612:39: error: invalid use of undefined type 'struct bpf_cgroup_link'
      cg_link = container_of(link, struct bpf_cgroup_link, link);
                                          ^
   include/linux/compiler_types.h:129:54: note: in definition of macro '__compiler_offsetof'
    #define __compiler_offsetof(a, b) __builtin_offsetof(a, b)
                                                         ^
   include/linux/kernel.h:997:21: note: in expansion of macro 'offsetof'
     ((type *)(__mptr - offsetof(type, member))); })
                        ^
   kernel/bpf/syscall.c:3612:13: note: in expansion of macro 'container_of'
      cg_link = container_of(link, struct bpf_cgroup_link, link);
                ^
>> kernel/bpf/syscall.c:3618:9: error: implicit declaration of function 'cgroup_bpf_replace' [-Werror=implicit-function-declaration]
      ret = cgroup_bpf_replace(cg_link->cgroup, cg_link,
            ^
   cc1: some warnings being treated as errors

vim +3612 kernel/bpf/syscall.c

  3576	
  3577	static int link_update(union bpf_attr *attr)
  3578	{
  3579		struct bpf_prog *old_prog = NULL, *new_prog;
  3580		enum bpf_prog_type ptype;
  3581		struct bpf_link *link;
  3582		u32 flags;
  3583		int ret;
  3584	
  3585		if (CHECK_ATTR(BPF_LINK_UPDATE))
  3586			return -EINVAL;
  3587	
  3588		flags = attr->link_update.flags;
  3589		if (flags & ~BPF_F_REPLACE)
  3590			return -EINVAL;
  3591	
  3592		link = bpf_link_get_from_fd(attr->link_update.link_fd);
  3593		if (IS_ERR(link))
  3594			return PTR_ERR(link);
  3595	
  3596		new_prog = bpf_prog_get(attr->link_update.new_prog_fd);
  3597		if (IS_ERR(new_prog))
  3598			return PTR_ERR(new_prog);
  3599	
  3600		if (flags & BPF_F_REPLACE) {
  3601			old_prog = bpf_prog_get(attr->link_update.old_prog_fd);
  3602			if (IS_ERR(old_prog)) {
  3603				ret = PTR_ERR(old_prog);
  3604				old_prog = NULL;
  3605				goto out_put_progs;
  3606			}
  3607		}
  3608	
  3609		if (link->ops == &bpf_cgroup_link_lops) {
  3610			struct bpf_cgroup_link *cg_link;
  3611	
> 3612			cg_link = container_of(link, struct bpf_cgroup_link, link);
  3613			ptype = attach_type_to_prog_type(cg_link->type);
  3614			if (ptype != new_prog->type) {
  3615				ret = -EINVAL;
  3616				goto out_put_progs;
  3617			}
> 3618			ret = cgroup_bpf_replace(cg_link->cgroup, cg_link,
  3619						 old_prog, new_prog);
  3620		} else {
  3621			ret = -EINVAL;
  3622		}
  3623	
  3624	out_put_progs:
  3625		if (old_prog)
  3626			bpf_prog_put(old_prog);
  3627		if (ret)
  3628			bpf_prog_put(new_prog);
  3629		return ret;
  3630	}
  3631	

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