On Mon, 2017-04-24 at 09:32 +0200, Hannes Reinecke wrote: > On 04/22/2017 01:40 AM, Bart Van Assche wrote: > > --- a/include/linux/blk-mq.h > > +++ b/include/linux/blk-mq.h > > @@ -121,6 +121,12 @@ struct blk_mq_ops { > > softirq_done_fn *complete; > > > > /* > > + * Used by the debugfs implementation to show driver-specific > > + * information about a request. > > + */ > > + void (*show_rq)(struct seq_file *m, struct request *rq); > > + > > + /* > > * Called when the block layer side of a hardware queue has been > > * set up, allowing the driver to allocate/init matching structures. > > * Ditto for exit/teardown. > > > > I don't really like this; what does happen if someone disabled > CONFIG_BLK_DEBUGFS? Won't we end up with a stale callback? Hello Hannes, How about surrounding (*show_rq)() function pointer with #ifdef CONFIG_BLK_DEBUGFS / #endif? Bart.