[PATCH 3/5] block: allow end_io based requests in the completion batch handling

[Jens Axboe <axboe@kernel.dk>]

With end_io handlers now being able to potentially pass ownership of
the request upon completion, we can allow requests with end_io handlers
in the batch completion handling.

Co-developed-by: Stefan Roesch <shr@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/blk-mq.c         | 13 +++++++++++--
 include/linux/blk-mq.h |  3 ++-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a4e018c82b7c..523a201b9acf 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -823,8 +823,10 @@ static void blk_complete_request(struct request *req)
 	 * can find how many bytes remain in the request
 	 * later.
 	 */
-	req->bio = NULL;
-	req->__data_len = 0;
+	if (!req->end_io) {
+		req->bio = NULL;
+		req->__data_len = 0;
+	};
 }
 
 /**
@@ -1055,6 +1057,13 @@ void blk_mq_end_request_batch(struct io_comp_batch *iob)
 
 		rq_qos_done(rq->q, rq);
 
+		/*
+		 * If end_io handler returns NONE, then it still has
+		 * ownership of the request.
+		 */
+		if (rq->end_io && rq->end_io(rq, 0) == RQ_END_IO_NONE)
+			continue;
+
 		WRITE_ONCE(rq->state, MQ_RQ_IDLE);
 		if (!req_ref_put_and_test(rq))
 			continue;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e6fa49dd6196..50811d0fb143 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -853,8 +853,9 @@ static inline bool blk_mq_add_to_batch(struct request *req,
 				       struct io_comp_batch *iob, int ioerror,
 				       void (*complete)(struct io_comp_batch *))
 {
-	if (!iob || (req->rq_flags & RQF_ELV) || req->end_io || ioerror)
+	if (!iob || (req->rq_flags & RQF_ELV) || ioerror)
 		return false;
+
 	if (!iob->complete)
 		iob->complete = complete;
 	else if (iob->complete != complete)
-- 
2.35.1