nvme: rename and document nvme_end_request

nvme_end_request is a bit misnamed, as it wraps around the
blk_mq_complete_* API.  It's semantics also are non-trivial, so give it
a more descriptive name and add a comment explaining the semantics.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Documentation/fault-injection/nvme-fault-injection.rst

@@ -3,7 +3,7 @@ NVMe Fault Injection
 Linux's fault injection framework provides a systematic way to support
 error injection via debugfs in the /sys/kernel/debug directory. When
 enabled, the default NVME_SC_INVALID_OPCODE with no retry will be
-injected into the nvme_end_request. Users can change the default status
+injected into the nvme_try_complete_req. Users can change the default status
 code and no retry flag via the debugfs. The list of Generic Command
 Status can be found in include/linux/nvme.h
 

drivers/nvme/host/fc.c

@@ -2035,7 +2035,7 @@ done:
 	}
 
 	__nvme_fc_fcpop_chk_teardowns(ctrl, op, opstate);
-	if (!nvme_end_request(rq, status, result))
+	if (!nvme_try_complete_req(rq, status, result))
 		nvme_fc_complete_rq(rq);
 
 check_error:

drivers/nvme/host/nvme.h

@@ -523,7 +523,13 @@ static inline u32 nvme_bytes_to_numd(size_t len)
 	return (len >> 2) - 1;
 }
 
-static inline bool nvme_end_request(struct request *req, __le16 status,
+/*
+ * Fill in the status and result information from the CQE, and then figure out
+ * if blk-mq will need to use IPI magic to complete the request, and if yes do
+ * so.  If not let the caller complete the request without an indirect function
+ * call.
+ */
+static inline bool nvme_try_complete_req(struct request *req, __le16 status,
 		union nvme_result result)
 {
 	struct nvme_request *rq = nvme_req(req);

drivers/nvme/host/pci.c

@@ -961,7 +961,7 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
 
 	req = blk_mq_tag_to_rq(nvme_queue_tagset(nvmeq), cqe->command_id);
 	trace_nvme_sq(req, cqe->sq_head, nvmeq->sq_tail);
-	if (!nvme_end_request(req, cqe->status, cqe->result))
+	if (!nvme_try_complete_req(req, cqe->status, cqe->result))
 		nvme_pci_complete_rq(req);
 }
 

drivers/nvme/host/rdma.c

@@ -1189,7 +1189,7 @@ static void nvme_rdma_end_request(struct nvme_rdma_request *req)
 
 	if (!refcount_dec_and_test(&req->ref))
 		return;
-	if (!nvme_end_request(rq, req->status, req->result))
+	if (!nvme_try_complete_req(rq, req->status, req->result))
 		nvme_rdma_complete_rq(rq);
 }
 

drivers/nvme/host/tcp.c

@@ -481,7 +481,7 @@ static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
 		return -EINVAL;
 	}
 
-	if (!nvme_end_request(rq, cqe->status, cqe->result))
+	if (!nvme_try_complete_req(rq, cqe->status, cqe->result))
 		nvme_complete_rq(rq);
 	queue->nr_cqe++;
 
@@ -672,7 +672,7 @@ static inline void nvme_tcp_end_request(struct request *rq, u16 status)
 {
 	union nvme_result res = {};
 
-	if (!nvme_end_request(rq, cpu_to_le16(status << 1), res))
+	if (!nvme_try_complete_req(rq, cpu_to_le16(status << 1), res))
 		nvme_complete_rq(rq);
 }
 

drivers/nvme/target/loop.c

@@ -115,7 +115,7 @@ static void nvme_loop_queue_response(struct nvmet_req *req)
 			return;
 		}
 
-		if (!nvme_end_request(rq, cqe->status, cqe->result))
+		if (!nvme_try_complete_req(rq, cqe->status, cqe->result))
 			nvme_loop_complete_rq(rq);
 	}
 }