block: add completion handler for fast path

The batched completions only deal with non-partial requests anyway,
and it doesn't deal with any requests that have errors. Add a completion
handler that assumes it's a full request and that it's all being ended
successfully.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -709,6 +709,47 @@ static void blk_print_req_error(struct request *req, blk_status_t status)
 		IOPRIO_PRIO_CLASS(req->ioprio));
 }
 
+/*
+ * Fully end IO on a request. Does not support partial completions, or
+ * errors.
+ */
+static void blk_complete_request(struct request *req)
+{
+	const bool is_flush = (req->rq_flags & RQF_FLUSH_SEQ) != 0;
+	int total_bytes = blk_rq_bytes(req);
+	struct bio *bio = req->bio;
+
+	trace_block_rq_complete(req, BLK_STS_OK, total_bytes);
+
+	if (!bio)
+		return;
+
+#ifdef CONFIG_BLK_DEV_INTEGRITY
+	if (blk_integrity_rq(req) && req_op(req) == REQ_OP_READ)
+		req->q->integrity.profile->complete_fn(req, total_bytes);
+#endif
+
+	blk_account_io_completion(req, total_bytes);
+
+	do {
+		struct bio *next = bio->bi_next;
+
+		/* Completion has already been traced */
+		bio_clear_flag(bio, BIO_TRACE_COMPLETION);
+		if (!is_flush)
+			bio_endio(bio);
+		bio = next;
+	} while (bio);
+
+	/*
+	 * Reset counters so that the request stacking driver
+	 * can find how many bytes remain in the request
+	 * later.
+	 */
+	req->bio = NULL;
+	req->__data_len = 0;
+}
+
 /**
  * blk_update_request - Complete multiple bytes without completing the request
  * @req:      the request being processed
@@ -922,7 +963,7 @@ void blk_mq_end_request_batch(struct io_comp_batch *iob)
 		prefetch(rq->bio);
 		prefetch(rq->rq_next);
 
-		blk_update_request(rq, BLK_STS_OK, blk_rq_bytes(rq));
+		blk_complete_request(rq);
 		if (iob->need_ts)
 			__blk_mq_end_request_acct(rq, now);