blk-mq-debugfs: Show zone locking information

When debugging the ZBC code in the mq-deadline scheduler it is very
important to know which zones are locked and which zones are not
locked. Hence this patch that exports the zone locking information
through debugfs.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq-debugfs.c

@@ -206,11 +206,27 @@ static ssize_t queue_write_hint_store(void *data, const char __user *buf,
 	return count;
 }
 
+static int queue_zone_wlock_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	unsigned int i;
+
+	if (!q->seq_zones_wlock)
+		return 0;
+
+	for (i = 0; i < blk_queue_nr_zones(q); i++)
+		if (test_bit(i, q->seq_zones_wlock))
+			seq_printf(m, "%u\n", i);
+
+	return 0;
+}
+
 static const struct blk_mq_debugfs_attr blk_mq_debugfs_queue_attrs[] = {
 	{ "poll_stat", 0400, queue_poll_stat_show },
 	{ "requeue_list", 0400, .seq_ops = &queue_requeue_list_seq_ops },
 	{ "state", 0600, queue_state_show, queue_state_write },
 	{ "write_hints", 0600, queue_write_hint_show, queue_write_hint_store },
+	{ "zone_wlock", 0400, queue_zone_wlock_show, NULL },
 	{ },
 };