linux-kernel - [PATCH for-next 1/1] null_blk: force complete for timeout request

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Date:   Fri, 29 May 2020 10:31:08 -0700
From:   Dongli Zhang <dongli.zhang@...cle.com>
To:     linux-block@...r.kernel.org
Cc:     axboe@...nel.dk, linux-kernel@...r.kernel.org
Subject: [PATCH for-next 1/1] null_blk: force complete for timeout request

The commit 7b11eab041da ("blk-mq: blk-mq: provide forced completion
method") exports new API to force a request to complete without error
injection.

There should be no error injection when completing a request by timeout
handler.

Otherwise, the below would hang because timeout handler is failed.

echo 100 > /sys/kernel/debug/fail_io_timeout/probability
echo 1000 > /sys/kernel/debug/fail_io_timeout/times
echo 1 > /sys/block/nullb0/io-timeout-fail
dd if=/dev/zero of=/dev/nullb0 bs=512 count=1 oflag=direct

With this patch, the timeout handler is able to complete the IO.

Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
---
 drivers/block/null_blk_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 6126f771ae99..87b31f9ca362 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -1423,7 +1423,7 @@ static bool should_requeue_request(struct request *rq)
 static enum blk_eh_timer_return null_timeout_rq(struct request *rq, bool res)
 {
 	pr_info("rq %p timed out\n", rq);
-	blk_mq_complete_request(rq);
+	blk_mq_force_complete_rq(rq);
 	return BLK_EH_DONE;
 }
 
-- 
2.17.1