[PATCH -next 2/2] block, bfq: make bfq_has_work() more accurate

[Yu Kuai]

bfq_has_work() is using busy_queues currently, which is not accurate
because bfq_queue is busy doesn't represent that it has requests. Since
bfqd aready has a counter 'queued' to record how many requests are in
bfq, use it instead of busy_queues.

Noted that bfq_has_work() can be called with 'bfqd->lock' held, thus the
lock can't be held in bfq_has_work() to protect 'bfqd->queued'.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 block/bfq-iosched.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 61750696e87f..1d2f8110c26b 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5063,11 +5063,11 @@ static bool bfq_has_work(struct blk_mq_hw_ctx *hctx)
 	struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
 
 	/*
-	 * Avoiding lock: a race on bfqd->busy_queues should cause at
+	 * Avoiding lock: a race on bfqd->queued should cause at
 	 * most a call to dispatch for nothing
 	 */
 	return !list_empty_careful(&bfqd->dispatch) ||
-		bfq_tot_busy_queues(bfqd) > 0;
+		READ_ONCE(bfqd->queued);
 }
 
 static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
-- 
2.31.1