[PATCH AUTOSEL 4.19 02/26] nvme-pci: Fix a race in controller removal

Sasha Levin
2019-10-09T17:31:16Z

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 ae0b01059fc6d..5d0f99bcc987f 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -111,10 +111,13 @@ 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