To avoid an error recovery deadlock where the keep alive work is waiting
for a request and thus can't be flushed to make progress for tearing down
the controller.  Also print the error code returned from
blk_mq_alloc_request to help debugging any future issues in this code.

Based on an earlier patch from Hannes Reinecke [off-list ref].

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
  drivers/nvme/host/core.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index bdeb3feae61899..8a4a9fe96cdf83 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c

@@ -1241,10 +1241,10 @@ static void nvme_keep_alive_work(struct work_struct *work)
  	}
  
  	rq = nvme_alloc_request(ctrl->admin_q, &ctrl->ka_cmd,
-				BLK_MQ_REQ_RESERVED);
+				BLK_MQ_REQ_RESERVED | BLK_MQ_REQ_NOWAIT);
  	if (IS_ERR(rq)) {
  		/* allocation failure, reset the controller */
-		dev_err(ctrl->device, "keep-alive failed\n");
+		dev_err(ctrl->device, "keep-alive failed: %ld\n", PTR_ERR(rq));
  		nvme_reset_ctrl(ctrl);
  		return;
  	}