Hi John,

I love your patch! Yet something to improve:

[auto build test ERROR on linux/master]
[also build test ERROR on drm-intel/for-linux-next drm-tip/drm-tip linus/master v5.13 next-20210629]
[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/John-Stultz/Generic-page-pool-deferred-freeing-for-system-dmabuf-hea/20210630-093515
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c54b245d011855ea91c5beff07f1db74143ce614
config: i386-randconfig-a006-20210628 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/79b275adef7ae3f4ace216d9127ed5a082b75d50
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review John-Stultz/Generic-page-pool-deferred-freeing-for-system-dmabuf-hea/20210630-093515
        git checkout 79b275adef7ae3f4ace216d9127ed5a082b75d50
        # save the attached .config to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

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 >>):

   ld: drivers/dma-buf/heaps/system_heap.o: in function `system_heap_create':
>> system_heap.c:(.text+0xb3): undefined reference to `drm_page_pool_init'
>> ld: system_heap.c:(.text+0xc7): undefined reference to `drm_page_pool_init'
   ld: system_heap.c:(.text+0xd8): undefined reference to `drm_page_pool_init'
   ld: drivers/dma-buf/heaps/system_heap.o: in function `system_heap_dma_buf_release':
>> system_heap.c:(.text+0x734): undefined reference to `drm_page_pool_add'
   ld: drivers/dma-buf/heaps/system_heap.o: in function `system_heap_allocate':
>> system_heap.c:(.text+0x81f): undefined reference to `drm_page_pool_remove'

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