[PATCH] nvme-pci: silence a lockdep complaint

[Sagi Grimberg]

lockdep complains about the timeout handler running concurrently with
the reset work which is syncing the IO request queues (which in turn
flushes the timeout work).

We know it cannot be the case because the ctrl state machine prevents
the timeout handler from disabling the ctrl when the reset work is
running (changing ctrl state to RESETTING will fail, and the state is not
terminal). If this assumption happens to break in the future, we won't
have lockdep to assist, but for the time being we are simply seeing
false-positive complaints from it...

Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki at wdc.com>
Suggested-by: Keith Busch <kbusch at kernel.org>
Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/host/pci.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 710043086dff..4a85b83b78f9 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2718,7 +2718,18 @@ static void nvme_reset_work(struct work_struct *work)
 	 */
 	if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
 		nvme_dev_disable(dev, false);
+	/*
+	 * lockdep complains about the timeout handler running concurrently
+	 * with this call. We know it cannot be the case because the ctrl state
+	 * machine prevents the timeout handler from disabling the ctrl when
+	 * the reset work is running (changing ctrl state to RESETTING will
+	 * fail, and the state is not terminal). If this assumption happens to
+	 * break in the future, we won't have lockdep to assist, but for the
+	 * time being we are simply seeing false-positive complaints from it...
+	 */
+	lockdep_off();
 	nvme_sync_queues(&dev->ctrl);
+	lockdep_on();
 
 	mutex_lock(&dev->shutdown_lock);
 	result = nvme_pci_enable(dev);
-- 
2.40.1