linux-kernel - [PATCH AUTOSEL 6.11 29/30] nvme-loop: flush off pending I/O while shutting down loop controller

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Message-ID: <20241023143012.2980728-29-sashal@kernel.org>
Date: Wed, 23 Oct 2024 10:29:54 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Nilay Shroff <nilay@...ux.ibm.com>,
	Christoph Hellwig <hch@....de>,
	Keith Busch <kbusch@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	sagi@...mberg.me,
	kch@...dia.com,
	linux-nvme@...ts.infradead.org
Subject: [PATCH AUTOSEL 6.11 29/30] nvme-loop: flush off pending I/O while shutting down loop controller

From: Nilay Shroff <nilay@...ux.ibm.com>

[ Upstream commit c199fac88fe7c749f88a0653e9f621b9f5a71cf1 ]

While shutting down loop controller, we first quiesce the admin/IO queue,
delete the admin/IO tag-set and then at last destroy the admin/IO queue.
However it's quite possible that during the window between quiescing and
destroying of the admin/IO queue, some admin/IO request might sneak in
and if that happens then we could potentially encounter a hung task
because shutdown operation can't forward progress until any pending I/O
is flushed off.

This commit helps ensure that before destroying the admin/IO queue, we
unquiesce the admin/IO queue so that any outstanding requests, which are
added after the admin/IO queue is quiesced, are now flushed to its
completion.

Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Nilay Shroff <nilay@...ux.ibm.com>
Signed-off-by: Keith Busch <kbusch@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/nvme/target/loop.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
index e32790d8fc260..a9d112d34d4f4 100644
--- a/drivers/nvme/target/loop.c
+++ b/drivers/nvme/target/loop.c
@@ -265,6 +265,13 @@ static void nvme_loop_destroy_admin_queue(struct nvme_loop_ctrl *ctrl)
 {
 	if (!test_and_clear_bit(NVME_LOOP_Q_LIVE, &ctrl->queues[0].flags))
 		return;
+	/*
+	 * It's possible that some requests might have been added
+	 * after admin queue is stopped/quiesced. So now start the
+	 * queue to flush these requests to the completion.
+	 */
+	nvme_unquiesce_admin_queue(&ctrl->ctrl);
+
 	nvmet_sq_destroy(&ctrl->queues[0].nvme_sq);
 	nvme_remove_admin_tag_set(&ctrl->ctrl);
 }
@@ -297,6 +304,12 @@ static void nvme_loop_destroy_io_queues(struct nvme_loop_ctrl *ctrl)
 		nvmet_sq_destroy(&ctrl->queues[i].nvme_sq);
 	}
 	ctrl->ctrl.queue_count = 1;
+	/*
+	 * It's possible that some requests might have been added
+	 * after io queue is stopped/quiesced. So now start the
+	 * queue to flush these requests to the completion.
+	 */
+	nvme_unquiesce_io_queues(&ctrl->ctrl);
 }
 
 static int nvme_loop_init_io_queues(struct nvme_loop_ctrl *ctrl)
-- 
2.43.0