Hi Ming,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on block/for-next]
[also build test ERROR on hch-configfs/for-next linus/master v5.14-rc4 next-20210805]
[cannot apply to linux/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Ming-Lei/loop-cleanup-charging-io-to-mem-blkcg/20210806-103713
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
config: nios2-randconfig-r032-20210804 (attached as .config)
compiler: nios2-linux-gcc (GCC) 10.3.0
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
        # https://github.com/0day-ci/linux/commit/6688155f28596e93bdb7ced3578e7ada41c09552
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Ming-Lei/loop-cleanup-charging-io-to-mem-blkcg/20210806-103713
        git checkout 6688155f28596e93bdb7ced3578e7ada41c09552
        # save the attached .config to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 make.cross O=build_dir ARCH=nios2 SHELL=/bin/bash drivers/block/

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 >>):

   drivers/block/loop.c: In function 'loop_rq_get_memcg_css':
>> drivers/block/loop.c:1017:35: error: invalid use of undefined type 'struct cgroup_subsys_state'
    1017 |   return memcg_get_e_css(blkcg_css->cgroup);
         |                                   ^~


vim +1017 drivers/block/loop.c

  1012	
  1013	static struct cgroup_subsys_state *loop_rq_get_memcg_css(
  1014			struct cgroup_subsys_state *blkcg_css)
  1015	{
  1016		if (blkcg_css)
> 1017			return memcg_get_e_css(blkcg_css->cgroup);
  1018		return NULL;
  1019	}
  1020	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org