linux-kernel - [PATCH 5.6 136/177] Revert "block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ

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Message-Id: <20200601174059.771446528@linuxfoundation.org>
Date:   Mon,  1 Jun 2020 19:54:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Bijan Mottahedeh <bijan.mottahedeh@...cle.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.6 136/177] Revert "block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ_NOWAIT"

From: Jens Axboe <axboe@...nel.dk>

[ Upstream commit b0beb28097fa04177b3769f4bb7a0d0d9c4ae76e ]

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@...r.kernel.org # v5.6
Reported-by: Bijan Mottahedeh <bijan.mottahedeh@...cle.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 60dc9552ef8d..92232907605c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -885,14 +885,11 @@ 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;
-- 
2.25.1