blk-mq: Fix poll_stat for new size-based bucketing.

Fixes an issue where the size of the poll_stat array in request_queue
does not match the size expected by the new size based bucketing for
IO completion polling.

Fixes: 720b8cc ("blk-mq: Add a polling specific stats function")
Signed-off-by: Stephen Bates <sbates@raithlin.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq-debugfs.c

@@ -159,14 +159,17 @@ static void print_stat(struct seq_file *m, struct blk_rq_stat *stat)
 static int queue_poll_stat_show(struct seq_file *m, void *v)
 {
 	struct request_queue *q = m->private;
+	int bucket;
 
-	seq_puts(m, "read: ");
-	print_stat(m, &q->poll_stat[READ]);
-	seq_puts(m, "\n");
+	for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS/2; bucket++) {
+		seq_printf(m, "read  (%d Bytes): ", 1 << (9+bucket));
+		print_stat(m, &q->poll_stat[2*bucket]);
+		seq_puts(m, "\n");
 
-	seq_puts(m, "write: ");
-	print_stat(m, &q->poll_stat[WRITE]);
-	seq_puts(m, "\n");
+		seq_printf(m, "write (%d Bytes): ",  1 << (9+bucket));
+		print_stat(m, &q->poll_stat[2*bucket+1]);
+		seq_puts(m, "\n");
+	}
 	return 0;
 }
 

block/blk-mq.c

@@ -42,8 +42,6 @@ static LIST_HEAD(all_q_list);
 static void blk_mq_poll_stats_start(struct request_queue *q);
 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
 
-/* Must be consisitent with function below */
-#define BLK_MQ_POLL_STATS_BKTS 16
 static int blk_mq_poll_stats_bkt(const struct request *rq)
 {
 	int ddir, bytes, bucket;

include/linux/blkdev.h

@@ -46,6 +46,9 @@ struct blk_stat_callback;
 #define BLKDEV_MIN_RQ	4
 #define BLKDEV_MAX_RQ	128	/* Default maximum */
 
+/* Must be consisitent with blk_mq_poll_stats_bkt() */
+#define BLK_MQ_POLL_STATS_BKTS 16
+
 /*
  * Maximum number of blkcg policies allowed to be registered concurrently.
  * Defined here to simplify include dependency.
@@ -517,7 +520,7 @@ struct request_queue {
 	int			poll_nsec;
 
 	struct blk_stat_callback	*poll_cb;
-	struct blk_rq_stat	poll_stat[2];
+	struct blk_rq_stat	poll_stat[BLK_MQ_POLL_STATS_BKTS];
 
 	struct timer_list	timeout;
 	struct work_struct	timeout_work;