nvme: fix misaccounting of nvme-mpath inflight I/O

Procedures for nvme-mpath IO accounting:

 1) initialize nvme_request and clear flags;
 2) set NVME_MPATH_IO_STATS and increase inflight counter when IO
    started;
 3) check NVME_MPATH_IO_STATS and decrease inflight counter when IO is
    done;

However, for the case nvme_fail_nonready_command(), both step 1) and 2)
are skipped, and if old nvme_request set NVME_MPATH_IO_STATS and then
request is reused, step 3) will still be executed, causing inflight I/O
counter to be negative.

Fix the problem by clearing nvme_request in nvme_fail_nonready_command().

Fixes: ea5e5f4 ("nvme-fabrics: avoid double completions in nvmf_fail_nonready_command")
Reported-by: Yi Zhang <[email protected]>
Closes: https://lore.kernel.org/all/CAHj4cs_+dauobyYyP805t33WMJVzOWj=7+51p4_j9rA63D9sog@mail.gmail.com/
Signed-off-by: Yu Kuai <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>

Author: YuKuai-huawei

drivers/nvme/host/core.c

@@ -764,6 +764,10 @@ blk_status_t nvme_fail_nonready_command(struct nvme_ctrl *ctrl,
 	    !test_bit(NVME_CTRL_FAILFAST_EXPIRED, &ctrl->flags) &&
 	    !blk_noretry_request(rq) && !(rq->cmd_flags & REQ_NVME_MPATH))
 		return BLK_STS_RESOURCE;
+
+	if (!(rq->rq_flags & RQF_DONTPREP))
+		nvme_clear_nvme_request(rq);
+
 	return nvme_host_path_error(rq);
 }
 EXPORT_SYMBOL_GPL(nvme_fail_nonready_command);