nvmet: Don't queue fatal error work if csts.cfs is set

In the transport, in case of an interal queue error like
error completion in rdma we trigger a fatal error. However,
multiple queues in the same controller can serr error completions
and we don't want to trigger fatal error work more than once.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/target/core.c

@@ -838,9 +838,13 @@ static void nvmet_fatal_error_handler(struct work_struct *work)
 
 void nvmet_ctrl_fatal_error(struct nvmet_ctrl *ctrl)
 {
+	mutex_lock(&ctrl->lock);
+	if (!(ctrl->csts & NVME_CSTS_CFS)) {
 		ctrl->csts |= NVME_CSTS_CFS;
 		INIT_WORK(&ctrl->fatal_err_work, nvmet_fatal_error_handler);
 		schedule_work(&ctrl->fatal_err_work);
+	}
+	mutex_unlock(&ctrl->lock);
 }
 EXPORT_SYMBOL_GPL(nvmet_ctrl_fatal_error);