Re: [PATCH v2] nvme: prevent warning triggered by nvme_stop_keep_alive

[Keith Busch <kbusch@kernel.org>]

On Mon, Feb 10, 2020 at 04:01:45PM -0800, James Smart wrote:
> Delayed keep alive work is queued on system workqueue and may be cancelled
> via nvme_stop_keep_alive from nvme_reset_wq, nvme_fc_wq or nvme_wq.
> 
> Check_flush_dependency detects mismatched attributes between the work-queue
> context used to cancel the keep alive work and system-wq. Specifically
> system-wq does not have the WQ_MEM_RECLAIM flag, whereas the contexts used
> to cancel keep alive work have WQ_MEM_RECLAIM flag.
> 
> Example warning:
> 
>   workqueue: WQ_MEM_RECLAIM nvme-reset-wq:nvme_fc_reset_ctrl_work [nvme_fc]
> 	is flushing !WQ_MEM_RECLAIM events:nvme_keep_alive_work [nvme_core]
> 
> To avoid the flags mismatch, delayed keep alive work is queued on nvme_wq.
> 
> However this creates a secondary concern where work and a request to cancel
> that work may be in the same work queue - namely err_work in the rdma and
> tcp transports, which will want to flush/cancel the keep alive work which
> will now be on nvme_wq.
> 
> After reviewing the transports, it looks like err_work can be moved to
> nvme_reset_wq. In fact that aligns them better with transition into
> RESETTING and performing related reset work in nvme_reset_wq.
> 
> Change nvme-rdma and nvme-tcp to perform err_work in nvme_reset_wq.
> 
> Signed-off-by: Nigel Kirkland <nigel.kirkland@broadcom.com>
> Signed-off-by: James Smart <jsmart2021@gmail.com>
> Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks James, applied to nvme-5.6-rc.

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