Re: [PATCH 1/4] mm, memcontrol: avoid duplicated memcg enable check

[kernel test robot <lkp@intel.com>]

Hi Kairui,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Kairui-Song/mm-memcontrol-avoid-duplicated-memcg-enable-check/20241203-024957
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20241202184154.19321-2-ryncsn%40gmail.com
patch subject: [PATCH 1/4] mm, memcontrol: avoid duplicated memcg enable check
config: arm-randconfig-002-20241203 (https://download.01.org/0day-ci/archive/20241203/202412030915.jyKBIDck-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241203/202412030915.jyKBIDck-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412030915.jyKBIDck-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/memcontrol.c: In function 'mem_cgroup_swapin_uncharge_swap':
>> mm/memcontrol.c:4618:17: error: implicit declaration of function '__mem_cgroup_uncharge_swap'; did you mean 'mem_cgroup_uncharge_swap'? [-Wimplicit-function-declaration]
    4618 |                 __mem_cgroup_uncharge_swap(entry, nr_pages);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~
         |                 mem_cgroup_uncharge_swap


vim +4618 mm/memcontrol.c

  4587	
  4588	/*
  4589	 * mem_cgroup_swapin_uncharge_swap - uncharge swap slot
  4590	 * @entry: the first swap entry for which the pages are charged
  4591	 * @nr_pages: number of pages which will be uncharged
  4592	 *
  4593	 * Call this function after successfully adding the charged page to swapcache.
  4594	 *
  4595	 * Note: This function assumes the page for which swap slot is being uncharged
  4596	 * is order 0 page.
  4597	 */
  4598	void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
  4599	{
  4600		/*
  4601		 * Cgroup1's unified memory+swap counter has been charged with the
  4602		 * new swapcache page, finish the transfer by uncharging the swap
  4603		 * slot. The swap slot would also get uncharged when it dies, but
  4604		 * it can stick around indefinitely and we'd count the page twice
  4605		 * the entire time.
  4606		 *
  4607		 * Cgroup2 has separate resource counters for memory and swap,
  4608		 * so this is a non-issue here. Memory and swap charge lifetimes
  4609		 * correspond 1:1 to page and swap slot lifetimes: we charge the
  4610		 * page to memory here, and uncharge swap when the slot is freed.
  4611		 */
  4612		if (!mem_cgroup_disabled() && do_memsw_account()) {
  4613			/*
  4614			 * The swap entry might not get freed for a long time,
  4615			 * let's not wait for it.  The page already received a
  4616			 * memory+swap charge, drop the swap entry duplicate.
  4617			 */
> 4618			__mem_cgroup_uncharge_swap(entry, nr_pages);
  4619		}
  4620	}
  4621	

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