mainline build failure due to 9c66dc94b62a ("bpf: Introduce css_task open-coded iterator kfuncs")

["Sudip Mukherjee (Codethink)" <sudipm.mukherjee@gmail.com>]

Hi All,

The latest mainline kernel branch fails to build mips decstation_64_defconfig,
decstation_defconfig and decstation_r4k_defconfig with the error:

kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_new':
kernel/bpf/task_iter.c:917:14: error: 'CSS_TASK_ITER_PROCS' undeclared (first use in this function)
  917 |         case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
      |              ^~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c:917:14: note: each undeclared identifier is reported only once for each function it appears in
kernel/bpf/task_iter.c:917:36: error: 'CSS_TASK_ITER_THREADED' undeclared (first use in this function)
  917 |         case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
      |                                    ^~~~~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c:925:60: error: invalid application of 'sizeof' to incomplete type 'struct css_task_iter'
  925 |         kit->css_it = bpf_mem_alloc(&bpf_global_ma, sizeof(struct css_task_iter));
      |                                                            ^~~~~~
kernel/bpf/task_iter.c:928:9: error: implicit declaration of function 'css_task_iter_start'; did you mean 'task_seq_start'? [-Werror=implicit-function-declaration]
  928 |         css_task_iter_start(css, flags, kit->css_it);
      |         ^~~~~~~~~~~~~~~~~~~
      |         task_seq_start
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_next':
kernel/bpf/task_iter.c:938:16: error: implicit declaration of function 'css_task_iter_next'; did you mean 'class_dev_iter_next'? [-Werror=implicit-function-declaration]
  938 |         return css_task_iter_next(kit->css_it);
      |                ^~~~~~~~~~~~~~~~~~
      |                class_dev_iter_next
kernel/bpf/task_iter.c:938:16: warning: returning 'int' from a function with return type 'struct task_struct *' makes pointer from integer without a cast [-Wint-conversion]
  938 |         return css_task_iter_next(kit->css_it);
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_destroy':
kernel/bpf/task_iter.c:947:9: error: implicit declaration of function 'css_task_iter_end' [-Werror=implicit-function-declaration]
  947 |         css_task_iter_end(kit->css_it);
      |         ^~~~~~~~~~~~~~~~~

git bisect pointed to 9c66dc94b62a ("bpf: Introduce css_task open-coded iterator kfuncs")

I will be happy to test any patch or provide any extra log if needed.

#regzbot introduced: 9c66dc94b62aef23300f05f63404afb8990920b4

-- 
Regards
Sudip