NVMe: Do not cancel command multiple times

Cancelling an already cancelled command does not do anything, so check
the command context before cancelling it, continuing if had already been
cancelled so we do not log the same problem every second if a device
stops responding.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

drivers/block/nvme-core.c

@@ -978,6 +978,8 @@ static void nvme_cancel_ios(struct nvme_queue *nvmeq, bool timeout)
 
 		if (timeout && !time_after(now, info[cmdid].timeout))
 			continue;
+		if (info[cmdid].ctx == CMD_CTX_CANCELLED)
+			continue;
 		dev_warn(nvmeq->q_dmadev, "Cancelling I/O %d\n", cmdid);
 		ctx = cancel_cmdid(nvmeq, cmdid, &fn);
 		fn(nvmeq->dev, ctx, &cqe);