[PATCH] nvme: Block ns inventory changes during admin

[keith.busch@intel.com (Keith Busch)]

The driver quiesces IO when the admin command effects say it may alter
namespaces.

A device that supports nvme namespace management may trigger a namespace
scan automatically. If this changes the namespace inventory by adding
more namespace, the driver's unquiesce sequence at the end of sending
the admin command may try to unfreeze a queue that isn't frozen,
breaking the freeze depth for future use.

Fix that by preventing scan work from altering the namespace list while
we are pairing freeze and unfreeze operations.

Reported-by: Wen Xiong <wenxiong at us.ibm.com>
Signed-off-by: Keith Busch <keith.busch at intel.com>
---
 drivers/nvme/host/core.c | 8 +++++++-
 drivers/nvme/host/nvme.h | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 150e49723c15..6a9dd68c0f4f 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1253,6 +1253,7 @@ static u32 nvme_passthru_start(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 	 * effects say only one namespace is affected.
 	 */
 	if (effects & (NVME_CMD_EFFECTS_LBCC | NVME_CMD_EFFECTS_CSE_MASK)) {
+		mutex_lock(&ctrl->scan_lock);
 		nvme_start_freeze(ctrl);
 		nvme_wait_freeze(ctrl);
 	}
@@ -1281,8 +1282,10 @@ static void nvme_passthru_end(struct nvme_ctrl *ctrl, u32 effects)
 	 */
 	if (effects & NVME_CMD_EFFECTS_LBCC)
 		nvme_update_formats(ctrl);
-	if (effects & (NVME_CMD_EFFECTS_LBCC | NVME_CMD_EFFECTS_CSE_MASK))
+	if (effects & (NVME_CMD_EFFECTS_LBCC | NVME_CMD_EFFECTS_CSE_MASK)) {
 		nvme_unfreeze(ctrl);
+		mutex_unlock(&ctrl->scan_lock);
+	}
 	if (effects & NVME_CMD_EFFECTS_CCC)
 		nvme_init_identify(ctrl);
 	if (effects & (NVME_CMD_EFFECTS_NIC | NVME_CMD_EFFECTS_NCC))
@@ -3401,6 +3404,7 @@ static void nvme_scan_work(struct work_struct *work)
 	if (nvme_identify_ctrl(ctrl, &id))
 		return;
 
+	mutex_lock(&ctrl->scan_lock);
 	nn = le32_to_cpu(id->nn);
 	if (ctrl->vs >= NVME_VS(1, 1, 0) &&
 	    !(ctrl->quirks & NVME_QUIRK_IDENTIFY_CNS)) {
@@ -3409,6 +3413,7 @@ static void nvme_scan_work(struct work_struct *work)
 	}
 	nvme_scan_ns_sequential(ctrl, nn);
 out_free_id:
+	mutex_unlock(&ctrl->scan_lock);
 	kfree(id);
 	down_write(&ctrl->namespaces_rwsem);
 	list_sort(NULL, &ctrl->namespaces, ns_cmp);
@@ -3652,6 +3657,7 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
 
 	ctrl->state = NVME_CTRL_NEW;
 	spin_lock_init(&ctrl->lock);
+	mutex_init(&ctrl->scan_lock);
 	INIT_LIST_HEAD(&ctrl->namespaces);
 	init_rwsem(&ctrl->namespaces_rwsem);
 	ctrl->dev = dev;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index ab961bdeea89..c4a1bb41abf0 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -154,6 +154,7 @@ struct nvme_ctrl {
 	enum nvme_ctrl_state state;
 	bool identified;
 	spinlock_t lock;
+	struct mutex scan_lock;
 	const struct nvme_ctrl_ops *ops;
 	struct request_queue *admin_q;
 	struct request_queue *connect_q;
-- 
2.14.4