[v2,3/7,RFC] nvme: Use BLK_MQ_S_STOPPED instead of QUEUE_FLAG_STOPPED in blk-mq code
diff mbox

Message ID 9faa7607-eb3e-ce41-b09e-1e10492a5f45@sandisk.com
State New
Headers show

Commit Message

Bart Van Assche Sept. 29, 2016, 12:02 a.m. UTC
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. 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(). Untested.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/core.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

Comments

Sagi Grimberg Oct. 5, 2016, 5:43 p.m. UTC | #1
> 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. 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(). Untested.

This looks good to me, but I know keith had all sort of
creative ways to challenge this are so I'd wait for his
input...
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Patch
diff mbox

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 4669c05..d791fba 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);
 	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);
 }
@@ -2080,10 +2080,6 @@  void nvme_stop_queues(struct nvme_ctrl *ctrl)
 
 	mutex_lock(&ctrl->namespaces_mutex);
 	list_for_each_entry(ns, &ctrl->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);
 	}
@@ -2097,7 +2093,6 @@  void nvme_start_queues(struct nvme_ctrl *ctrl)
 
 	mutex_lock(&ctrl->namespaces_mutex);
 	list_for_each_entry(ns, &ctrl->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);
 	}