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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Balbir Singh <sblbir@amzn.com>,
        Keith Busch <kbusch@kernel.org>,
        Sagi Grimberg <sagi@grimberg.me>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.3 005/197] nvme-pci: Fix a race in controller removal
Date:   Sun, 27 Oct 2019 21:58:43 +0100
Message-Id: <20191027203351.981022129@linuxfoundation.org>
In-Reply-To: <20191027203351.684916567@linuxfoundation.org>
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From: Balbir Singh <sblbir@amzn.com>

[ Upstream commit b224726de5e496dbf78147a66755c3d81e28bdd2 ]

User space programs like udevd may try to read to partitions at the
same time the driver detects a namespace is unusable, and may deadlock
if revalidate_disk() is called while such a process is waiting to
enter the frozen queue. On detecting a dead namespace, move the disk
revalidate after unblocking dispatchers that may be holding bd_butex.

changelog Suggested-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Balbir Singh <sblbir@amzn.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/nvme/host/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index d3d6b7bd69033..28217cee5e762 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -103,10 +103,13 @@ static void nvme_set_queue_dying(struct nvme_ns *ns)
 	 */
 	if (!ns->disk || test_and_set_bit(NVME_NS_DEAD, &ns->flags))
 		return;
-	revalidate_disk(ns->disk);
 	blk_set_queue_dying(ns->queue);
 	/* Forcibly unquiesce queues to avoid blocking dispatch */
 	blk_mq_unquiesce_queue(ns->queue);
+	/*
+	 * Revalidate after unblocking dispatchers that may be holding bd_butex
+	 */
+	revalidate_disk(ns->disk);
 }
 
 static void nvme_queue_scan(struct nvme_ctrl *ctrl)
-- 
2.20.1