The pernicious USB-stick stall problem

As a "good" and not "perfect" solution, why not make dirty_background_ratio and dirty_ratio a percentage of some fixed value, and allow arbitrarily large* percentages?

* - dirty_background_ratio is a signed 32-bit value. If our "fixed value" were 1MiB, you could specify up to 2TiB of buffer space in the future. When we get to 128-bit architectures, we might want to increase the size of dirty_background_ratio to accommodate larger buffers.