Re: [PATCH 11/12] nvme: Use BLK_MQ_S_STOPPED instead of QUEUE_FLAG_STOPPED in blk-mq code

[Sagi Grimberg]

Looks good,

Reviewed-by: Sagi Grimberg 
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[PATCH 11/12] nvme: Use BLK_MQ_S_STOPPED instead of QUEUE_FLAG_STOPPED in blk-mq code

[Bart Van Assche]

Make nvme_requeue_req() check BLK_MQ_S_STOPPED instead of
QUEUE_FLAG_STOPPED. Remove the QUEUE_FLAG_STOPPED manipulations
that became superfluous because of this change. Change
blk_queue_stopped() tests into blk_mq_queue_stopped().

This patch fixes a race condition: using queue_flag_clear_unlocked()
is not safe if any other function that manipulates the queue flags
can be called concurrently, e.g. blk_cleanup_queue().

Signed-off-by: Bart Van Assche 
Reviewed-by: Christoph Hellwig 
Cc: Keith Busch 
Cc: Christoph Hellwig 
Cc: Sagi Grimberg 
---
 drivers/nvme/host/core.c | 7 +--
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 7bb73ba..b662416 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -205,7 +205,7 @@ void nvme_requeue_req(struct request *req)
 
blk_mq_requeue_request(req, false);
spin_lock_irqsave(req->q->queue_lock, flags);
-   if (!blk_queue_stopped(req->q))
+   if (!blk_mq_queue_stopped(req->q))
blk_mq_kick_requeue_list(req->q);
spin_unlock_irqrestore(req->q->queue_lock, flags);
 }
@@ -2079,10 +2079,6 @@ void nvme_stop_queues(struct nvme_ctrl *ctrl)
 
mutex_lock(>namespaces_mutex);
list_for_each_entry(ns, >namespaces, list) {
-   spin_lock_irq(ns->queue->queue_lock);
-   queue_flag_set(QUEUE_FLAG_STOPPED, ns->queue);
-   spin_unlock_irq(ns->queue->queue_lock);
-
blk_mq_cancel_requeue_work(ns->queue);
blk_mq_stop_hw_queues(ns->queue);
}
@@ -2096,7 +2092,6 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
 
mutex_lock(>namespaces_mutex);
list_for_each_entry(ns, >namespaces, list) {
-   queue_flag_clear_unlocked(QUEUE_FLAG_STOPPED, ns->queue);
blk_mq_start_stopped_hw_queues(ns->queue, true);
blk_mq_kick_requeue_list(ns->queue);
}
-- 
2.10.1

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