From: Chao Leng <lengchao@xxxxxxxxxx> REQ_FAILFAST_TRANSPORT was designed for SCSI, because the SCSI protocol does not define the local retry mechanism. SCSI implements a fuzzy local retry mechanism, so REQ_FAILFAST_TRANSPORT is needed to allow higher-level multipathing software to perform failover/retry. NVMe is different with SCSI about this. It defines a local retry mechanism and path error codes, so NVMe should retry local for non path error. If path related error, whether to retry and how to retry is still determined by higher-level multipathing's failover. Unlike SCSI, NVMe shouldn't prevent retry if REQ_FAILFAST_TRANSPORT because NVMe's local retry is needed -- as is NVMe specific logic to categorize whether an error is path related. In this way, the mechanism of NVMe multipath or other multipath are now equivalent. The mechanism is: non path related error will be retried locally, path related error is handled by multipath. Signed-off-by: Chao Leng <lengchao@xxxxxxxxxx> [snitzer: edited header for grammar and clarity, also added code comment] Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> --- drivers/nvme/host/core.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 540d6fd8ffef..4134cf3c7e48 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -306,7 +306,14 @@ static inline enum nvme_disposition nvme_decide_disposition(struct request *req) if (likely(nvme_req(req)->status == 0)) return COMPLETE; - if (blk_noretry_request(req) || + /* + * REQ_FAILFAST_TRANSPORT is set by upper layer software that + * handles multipathing. Unlike SCSI, NVMe's error handling was + * specifically designed to handle local retry for non-path errors. + * As such, allow NVMe's local retry mechanism to be used for + * requests marked with REQ_FAILFAST_TRANSPORT. + */ + if ((req->cmd_flags & (REQ_FAILFAST_DEV | REQ_FAILFAST_DRIVER)) || (nvme_req(req)->status & NVME_SC_DNR) || nvme_req(req)->retries >= nvme_max_retries) return COMPLETE; -- 2.15.0
