linux-kernel - [PATCH] nvme-pci: use NOWAIT flag for nvme_set_host

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Date:   Mon, 29 Jan 2018 11:07:35 +0800
From:   Jianchao Wang <jianchao.w.wang@...cle.com>
To:     keith.busch@...el.com, axboe@...com, hch@....de, sagi@...mberg.me
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] nvme-pci: use NOWAIT flag for nvme_set_host_mem

nvme_set_host_mem will invoke nvme_alloc_request without NOWAIT
flag, it is unsafe for nvme_dev_disable. The adminq driver tags
may have been used up when the previous outstanding adminq requests
cannot be completed due to some hardware error. We have to depend
on the timeout path to complete the previous outstanding adminq
requests and free the tags.
However, nvme_timeout will invoke nvme_dev_disable and try to
get the shutdown_lock which is held by another context who is
sleeping to wait for the tags to be freed by timeout path. A
deadlock comes up.

To fix it, let nvme_set_host_mem use NOWAIT flag.

Signed-off-by: Jianchao Wang <jianchao.w.wang@...cle.com>
---
 drivers/nvme/host/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 6fe7af0..9532529 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1736,7 +1736,8 @@ static int nvme_set_host_mem(struct nvme_dev *dev, u32 bits)
 	c.features.dword14	= cpu_to_le32(upper_32_bits(dma_addr));
 	c.features.dword15	= cpu_to_le32(dev->nr_host_mem_descs);

-	ret = nvme_submit_sync_cmd(dev->ctrl.admin_q, &c, NULL, 0);
+	ret = __nvme_submit_sync_cmd(dev->ctrl.admin_q, &c, NULL, NULL, 0, 0,
+			NVME_QID_ANY, 0, BLK_MQ_REQ_NOWAIT);
 	if (ret) {
 		dev_warn(dev->ctrl.device,
 			 "failed to set host mem (err %d, flags %#x).\n",
-- 
2.7.4