Hi Hillf,

[FYI, it's a private test report for your RFC patch.]
[auto build test ERROR on linus/master]
[cannot apply to v5.4-rc4 next-20191021]
[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/Hillf-Danton/memcg-add-memcg-lru-for-page-reclaiming/20191022-082625
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 7d194c2100ad2a6dded545887d02754948ca5241
config: x86_64-lkp (attached as .config)
compiler: gcc-7 (Debian 7.4.0-14) 7.4.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

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

All errors (new ones prefixed by >>):

   mm/memcontrol.c: In function 'reclaim_high':
   mm/memcontrol.c:2385:8: error: 'start' undeclared (first use in this function); did you mean 'stat'?
       if (start != memcg) {
           ^~~~~
           stat
   mm/memcontrol.c:2385:8: note: each undeclared identifier is reported only once for each function it appears in
>> mm/memcontrol.c:2386:5: error: implicit declaration of function 'memcg_add_lru'; did you mean 'numa_add_cpu'? [-Werror=implicit-function-declaration]
        memcg_add_lru(memcg);
        ^~~~~~~~~~~~~
        numa_add_cpu
   mm/memcontrol.c: In function 'mem_cgroup_soft_limit_reclaim':
   mm/memcontrol.c:3202:30: error: implicit declaration of function 'memcg_pick_lru'; did you mean 'lock_page_lru'? [-Werror=implicit-function-declaration]
      struct mem_cgroup *memcg = memcg_pick_lru();
                                 ^~~~~~~~~~~~~~
                                 lock_page_lru
   mm/memcontrol.c:3202:30: warning: initialization makes pointer from integer without a cast [-Wint-conversion]
   mm/memcontrol.c: In function 'mem_cgroup_alloc':
   mm/memcontrol.c:5119:26: error: 'struct mem_cgroup' has no member named 'lru_node'; did you mean 'scan_nodes'?
      INIT_LIST_HEAD(&memcg->lru_node);
                             ^~~~~~~~
                             scan_nodes
   cc1: some warnings being treated as errors

vim +2386 mm/memcontrol.c

  2372	
  2373	static void reclaim_high(struct mem_cgroup *memcg,
  2374				 unsigned int nr_pages,
  2375				 gfp_t gfp_mask)
  2376	{
  2377	#ifdef CONFIG_MEMCG_LRU
  2378		struct mem_cgroup *start = memcg;
  2379	#endif
  2380		do {
  2381			if (page_counter_read(&memcg->memory) <= memcg->high)
  2382				continue;
  2383			memcg_memory_event(memcg, MEMCG_HIGH);
  2384			if (IS_ENABLED(CONFIG_MEMCG_LRU))
> 2385				if (start != memcg) {
> 2386					memcg_add_lru(memcg);
  2387					return;
  2388				}
  2389			try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
  2390		} while ((memcg = parent_mem_cgroup(memcg)));
  2391	}
  2392	

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