From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 28 May 2020 13:19:29 -0600
Subject: [PATCH] Revert "block: end bio with BLK_STS_AGAIN in case of non-mq
 devs and REQ_NOWAIT"
References: bsc#1175995,jsc#SLE-15608
Git-commit: b0beb28097fa04177b3769f4bb7a0d0d9c4ae76e
Patch-mainline: v5.7

This reverts commit c58c1f83436b501d45d4050fd1296d71a9760bcb.

io_uring does do the right thing for this case, and we're still returning
-EAGAIN to userspace for the cases we don't support. Revert this change
to avoid doing endless spins of resubmits.

Cc: stable@vger.kernel.org # v5.6
Reported-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 block/blk-core.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 8fc42e1e6cc9..a63df58b745d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -931,14 +931,11 @@ generic_make_request_checks(struct bio *bio)
 	}
 
 	/*
-	 * Non-mq queues do not honor REQ_NOWAIT, so complete a bio
-	 * with BLK_STS_AGAIN status in order to catch -EAGAIN and
-	 * to give a chance to the caller to repeat request gracefully.
+	 * For a REQ_NOWAIT based request, return -EOPNOTSUPP
+	 * if queue is not a request based queue.
 	 */
-	if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q)) {
-		status = BLK_STS_AGAIN;
-		goto end_io;
-	}
+	if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q))
+		goto not_supported;
 
 	if (should_fail_bio(bio))
 		goto end_io;
-- 
2.16.4