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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Ming Lei <ming.lei@redhat.com>, Wen Xiong <wenxiong@us.ibm.com>,
        Jens Axboe <axboe@kernel.dk>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.14 091/110] block: drain queue before waiting
 for q_usage_counter becoming zero
Thread-Topic: [PATCH AUTOSEL for 4.14 091/110] block: drain queue before
 waiting for q_usage_counter becoming zero
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Date:   Sat, 3 Feb 2018 18:01:26 +0000
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From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 454be724f6f99cc7e7bbf15067128be9868186c6 ]

Now we track legacy requests with .q_usage_counter in commit 055f6e18e08f
("block: Make q_usage_counter also track legacy requests"), but that
commit never runs and drains legacy queue before waiting for this counter
becoming zero, then IO hang is caused in the test of pulling disk during IO=
.

This patch fixes the issue by draining requests before waiting for
q_usage_counter becoming zero, both Mauricio and chenxiang reported this
issue, and observed that it can be fixed by this patch.

Link: https://marc.info/?l=3Dlinux-block&m=3D151192424731797&w=3D2
Fixes: 055f6e18e08f("block: Make q_usage_counter also track legacy requests=
")
Cc: Wen Xiong <wenxiong@us.ibm.com>
Tested-by: "chenxiang (M)" <chenxiang66@hisilicon.com>
Tested-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 block/blk-core.c | 9 +++++++--
 block/blk-mq.c   | 2 ++
 block/blk.h      | 2 ++
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 7b30bf10b1d4..1aec210405ff 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -531,6 +531,13 @@ static void __blk_drain_queue(struct request_queue *q,=
 bool drain_all)
 	}
 }
=20
+void blk_drain_queue(struct request_queue *q)
+{
+	spin_lock_irq(q->queue_lock);
+	__blk_drain_queue(q, true);
+	spin_unlock_irq(q->queue_lock);
+}
+
 /**
  * blk_queue_bypass_start - enter queue bypass mode
  * @q: queue of interest
@@ -655,8 +662,6 @@ void blk_cleanup_queue(struct request_queue *q)
 	 */
 	blk_freeze_queue(q);
 	spin_lock_irq(lock);
-	if (!q->mq_ops)
-		__blk_drain_queue(q, true);
 	queue_flag_set(QUEUE_FLAG_DEAD, q);
 	spin_unlock_irq(lock);
=20
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 98a18609755e..b60798a30ea2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -159,6 +159,8 @@ void blk_freeze_queue(struct request_queue *q)
 	 * exported to drivers as the only user for unfreeze is blk_mq.
 	 */
 	blk_freeze_queue_start(q);
+	if (!q->mq_ops)
+		blk_drain_queue(q);
 	blk_mq_freeze_queue_wait(q);
 }
=20
diff --git a/block/blk.h b/block/blk.h
index 85be8b232b37..b2c287c2c6a3 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -362,4 +362,6 @@ static inline void blk_queue_bounce(struct request_queu=
e *q, struct bio **bio)
 }
 #endif /* CONFIG_BOUNCE */
=20
+extern void blk_drain_queue(struct request_queue *q);
+
 #endif /* BLK_INTERNAL_H */
--=20
2.11.0