[$] Is it time to remove ZONE_DMA?

The DMA zone (ZONE_DMA) is a memory-management holdover from thedistant past. Once upon a time, many devices (those on the ISA bus inparticular) could only use 24 bits for DMA addresses, and were thuslimited to the bottom 16MB of memory. Such devices are hard to find oncontemporary computers. Luis Rodriguez scheduled the lastmemory-management-track session of the 2018 Linux Storage, Filesystem, andMemory-Management Summit to discuss whether the time has come to removeZONE_DMA altogether.