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

[ming.lei@redhat.com (Ming Lei)]

On Mon, Jul 22, 2019@08:27:32AM -0700, Bart Van Assche wrote:
> 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 at mellanox.com>
> > Cc: Sagi Grimberg <sagi at grimberg.me>
> > Cc: Keith Busch <keith.busch at intel.com>
> > Cc: Christoph Hellwig <hch at lst.de>
> > Signed-off-by: Ming Lei <ming.lei at 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?

The commit log did mention the point:

	Before aborting in-flight requests, all IO queues have been shutdown.

which implies that no concurrent normal completion.

Thanks,
Ming