Hi John,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[cannot apply to v5.4-rc1 next-20191002]
[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/John-Stultz/DMA-BUF-Heaps-destaging-ION/20191003-042849
config: mips-allmodconfig (attached as .config)
compiler: mips-linux-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=mips 

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

All errors (new ones prefixed by >>):

   drivers/dma-buf/heaps/heap-helpers.c: In function 'dma_heap_map_kernel':
>> drivers/dma-buf/heaps/heap-helpers.c:43:10: error: implicit declaration of function 'vmap'; did you mean 'bmap'? [-Werror=implicit-function-declaration]
     vaddr = vmap(buffer->pages, buffer->pagecount, VM_MAP, PAGE_KERNEL);
             ^~~~
             bmap
>> drivers/dma-buf/heaps/heap-helpers.c:43:49: error: 'VM_MAP' undeclared (first use in this function); did you mean 'VM_MPX'?
     vaddr = vmap(buffer->pages, buffer->pagecount, VM_MAP, PAGE_KERNEL);
                                                    ^~~~~~
                                                    VM_MPX
   drivers/dma-buf/heaps/heap-helpers.c:43:49: note: each undeclared identifier is reported only once for each function it appears in
   drivers/dma-buf/heaps/heap-helpers.c: In function 'dma_heap_buffer_destroy':
>> drivers/dma-buf/heaps/heap-helpers.c:54:3: error: implicit declaration of function 'vunmap'; did you mean 'kunmap'? [-Werror=implicit-function-declaration]
      vunmap(buffer->vaddr);
      ^~~~~~
      kunmap
   cc1: some warnings being treated as errors

vim +43 drivers/dma-buf/heaps/heap-helpers.c

    38	
    39	static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer)
    40	{
    41		void *vaddr;
    42	
  > 43		vaddr = vmap(buffer->pages, buffer->pagecount, VM_MAP, PAGE_KERNEL);
    44		if (!vaddr)
    45			return ERR_PTR(-ENOMEM);
    46	
    47		return vaddr;
    48	}
    49	
    50	static void dma_heap_buffer_destroy(struct heap_helper_buffer *buffer)
    51	{
    52		if (buffer->vmap_cnt > 0) {
    53			WARN("%s: buffer still mapped in the kernel\n", __func__);
  > 54			vunmap(buffer->vaddr);
    55		}
    56	
    57		buffer->free(buffer);
    58	}
    59	

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