Comment 820 for bug 500069

Per device dirty bytes configuration. Patch is not ideal, i'm make it for smoothly flash drive wriring by passing smaller value of dirty byte per removeable device.

>> Path
# ls /sys/block/sdc/bdi/
dirty_background_bytes dirty_background_ratio dirty_bytes dirty_ratio max_ratio min_pages_to_flush min_ratio power read_ahead_kb stable_pages_required subsystem uevent

>> udev Rule for removeables device
# cat /etc/udev/rules.d/90-dirty-flash.rules
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{removable}=="1", ATTR{bdi/dirty_bytes}="4194304"