Re: [PATCH v3 3/5] nvme-fabrics: avoid double request completion for nvmf_fail_nonready_command

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On 1/21/21 8:03 AM, Chao Leng wrote:
When reconnect, the request may be completed with NVME_SC_HOST_PATH_ERROR
in nvmf_fail_nonready_command. The state of request will be changed to
MQ_RQ_IN_FLIGHT before call nvme_complete_rq. If free the request
asynchronously such as in nvme_submit_user_cmd, in extreme scenario
the request may be completed again in tear down process.
nvmf_fail_nonready_command do not need calling blk_mq_start_request
before complete the request. nvmf_fail_nonready_command should set
the state of request to MQ_RQ_COMPLETE before complete the request.


So what you are saying is that there is a race condition between
blk_mq_start_request()
and
nvme_complete_request()

Signed-off-by: Chao Leng <lengchao@xxxxxxxxxx>
---
  drivers/nvme/host/fabrics.c | 4 +---
  1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 72ac00173500..874e4320e214 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -553,9 +553,7 @@ blk_status_t nvmf_fail_nonready_command(struct nvme_ctrl *ctrl,
  	    !blk_noretry_request(rq) && !(rq->cmd_flags & REQ_NVME_MPATH))
  		return BLK_STS_RESOURCE;
- nvme_req(rq)->status = NVME_SC_HOST_PATH_ERROR;
-	blk_mq_start_request(rq);
-	nvme_complete_rq(rq);
+	nvme_complete_failed_req(rq);
  	return BLK_STS_OK;
  }
  EXPORT_SYMBOL_GPL(nvmf_fail_nonready_command);
I'd rather have 'nvme_complete_failed_req()' accept the status as
argument, like

nvme_complete_failed_request(rq, NVME_SC_HOST_PATH_ERROR)

that way it's obvious what is happening, and the status isn't hidden in the function.

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
hare@xxxxxxx                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer



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