[PATCH 5.5 123/176] nvme-pci: Hold cq_poll_lock while completing CQEs

[Greg Kroah-Hartman]

From: Bijan Mottahedeh <bijan.mottahedeh@xxxxxxxxxx>

commit 9515743bfb39c61aaf3d4f3219a645c8d1fe9a0e upstream.

Completions need to consumed in the same order the controller submitted
them, otherwise future completion entries may overwrite ones we haven't
handled yet. Hold the nvme queue's poll lock while completing new CQEs to
prevent another thread from freeing command tags for reuse out-of-order.

Fixes: dabcefab45d3 ("nvme: provide optimized poll function for separate poll queues")
Signed-off-by: Bijan Mottahedeh <bijan.mottahedeh@xxxxxxxxxx>
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/nvme/host/pci.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1078,9 +1078,9 @@ static int nvme_poll(struct blk_mq_hw_ct
 
 	spin_lock(&nvmeq->cq_poll_lock);
 	found = nvme_process_cq(nvmeq, &start, &end, -1);
+	nvme_complete_cqes(nvmeq, start, end);
 	spin_unlock(&nvmeq->cq_poll_lock);
 
-	nvme_complete_cqes(nvmeq, start, end);
 	return found;
 }