The dma-buf counter is a metric for mapped memory used by it's clients.
It is a shared buffer that is typically used for interprocess communication
or process to hardware communication. In android we used to have ION,. but
it is now replaced with dma-buf. ION had some overview metrics that was similar.
V1
initial version. Add dma-buf counter
V2
Fix build depencendy error suggested by Matthew Wilcox
Extent commit message sugged by Köning
V3
Change variable and function names.
V4
Fix function name in code doc
Reported-by: kernel test robot <l...@intel.com>
V5
Removed EXPORT_SYMBOL_GPL suggested by Muchun Song
V6
Made it a patch set, Adding a addional patch for
printing dma-buf counter in show_mem.
Suggested by Michal Hocko.
