This provides the infrastructure for schedulers to expose their internal
state through debugfs. We add a list of queue attributes and a list of
hctx attributes to struct elevator_type and wire them up when switching
schedulers.
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>

Add missing seq_file.h header in blk-mq-debugfs.h
Signed-off-by: NJens Axboe <axboe@fb.com>