block: only allocate poll_stats if there's a user of them

This is essentially never used, yet it's about 1/3rd of the total
queue size. Allocate it when needed, and don't embed it in the queue.

Kill the queue flag for this while at it, since we can just check the
assigned pointer now.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 18 insertions, 0 deletions

diff --git a/block/blk-stat.c b/block/blk-stat.c
index ae3dd1fb8e61..efb2a80db906 100644
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -219,3 +219,21 @@ void blk_free_queue_stats(struct blk_queue_stats *stats)
 
 	kfree(stats);
 }
+
+bool blk_stats_alloc_enable(struct request_queue *q)
+{
+	struct blk_rq_stat *poll_stat;
+
+	poll_stat = kcalloc(BLK_MQ_POLL_STATS_BKTS, sizeof(*poll_stat),
+				GFP_ATOMIC);
+	if (!poll_stat)
+		return false;
+
+	if (cmpxchg(&q->poll_stat, NULL, poll_stat) != NULL) {
+		kfree(poll_stat);
+		return true;
+	}
+
+	blk_stat_add_callback(q, q->poll_cb);
+	return false;
+}