FM / trace

/sys/devices/virtual/block/loop2/trace

Name	Size	Mode	Actions
act_mask	4096	0644	edit dl rm
enable	4096	0644	edit dl rm
end_lba	4096	0644	edit dl rm
pid	4096	0644	edit dl rm
start_lba	4096	0644	edit dl rm

Edit: /sys/devices/virtual/block/loop2/trace/enable (4096B)

cmd: