Re: [PATCH 3/5] nvme: don't abort completed request in nvme_cancel_request

[Bart Van Assche <bvanassche@acm.org>]

On 7/21/19 10:39 PM, Ming Lei wrote:
> Before aborting in-flight requests, all IO queues have been shutdown.
> However, request's completion fn may not be done yet because it may
> be scheduled to run via IPI.
> 
> So don't abort one request if it is marked as completed, otherwise
> we may abort one normal completed request.
> 
> Cc: Max Gurtovoy <maxg@mellanox.com>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Cc: Keith Busch <keith.busch@intel.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   drivers/nvme/host/core.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index cc09b81fc7f4..cb8007cce4d1 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -285,6 +285,10 @@ EXPORT_SYMBOL_GPL(nvme_complete_rq);
>   
>   bool nvme_cancel_request(struct request *req, void *data, bool reserved)
>   {
> +	/* don't abort one completed request */
> +	if (blk_mq_request_completed(req))
> +		return;
> +
>   	dev_dbg_ratelimited(((struct nvme_ctrl *) data)->device,
>   				"Cancelling I/O %d", req->tag);

Something I probably already asked before: what prevents that 
nvme_cancel_request() is executed concurrently with the completion 
handler of the same request?

Thanks,

Bart.