nvmet-rdma: Correctly handle RDMA device hot removal
When configuring a device attached listener, we may
see device removal events. In this case we return a
non-zero return code from the cm event handler which
implicitly destroys the cm_id. It is possible that in
the future the user will remove this listener and by
that trigger a second call to rdma_destroy_id on an
already destroyed cm_id -> BUG.
In addition, when a queue bound (active session) cm_id
generates a DEVICE_REMOVAL event we must guarantee all
resources are cleaned up by the time we return from the
event handler.
Introduce nvmet_rdma_device_removal which addresses
(or at least attempts to) both scenarios.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index e06d504..48c8118 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -77,6 +77,7 @@
NVMET_RDMA_Q_CONNECTING,
NVMET_RDMA_Q_LIVE,
NVMET_RDMA_Q_DISCONNECTING,
+ NVMET_RDMA_IN_DEVICE_REMOVAL,
};
struct nvmet_rdma_queue {
@@ -984,7 +985,10 @@
struct nvmet_rdma_device *dev = queue->dev;
nvmet_rdma_free_queue(queue);
- rdma_destroy_id(cm_id);
+
+ if (queue->state != NVMET_RDMA_IN_DEVICE_REMOVAL)
+ rdma_destroy_id(cm_id);
+
kref_put(&dev->ref, nvmet_rdma_free_dev);
}
@@ -1233,8 +1237,9 @@
switch (queue->state) {
case NVMET_RDMA_Q_CONNECTING:
case NVMET_RDMA_Q_LIVE:
- disconnect = true;
queue->state = NVMET_RDMA_Q_DISCONNECTING;
+ case NVMET_RDMA_IN_DEVICE_REMOVAL:
+ disconnect = true;
break;
case NVMET_RDMA_Q_DISCONNECTING:
break;
@@ -1272,6 +1277,62 @@
schedule_work(&queue->release_work);
}
+/**
+ * nvme_rdma_device_removal() - Handle RDMA device removal
+ * @queue: nvmet rdma queue (cm id qp_context)
+ * @addr: nvmet address (cm_id context)
+ *
+ * DEVICE_REMOVAL event notifies us that the RDMA device is about
+ * to unplug so we should take care of destroying our RDMA resources.
+ * This event will be generated for each allocated cm_id.
+ *
+ * Note that this event can be generated on a normal queue cm_id
+ * and/or a device bound listener cm_id (where in this case
+ * queue will be null).
+ *
+ * we claim ownership on destroying the cm_id. For queues we move
+ * the queue state to NVMET_RDMA_IN_DEVICE_REMOVAL and for port
+ * we nullify the priv to prevent double cm_id destruction and destroying
+ * the cm_id implicitely by returning a non-zero rc to the callout.
+ */
+static int nvmet_rdma_device_removal(struct rdma_cm_id *cm_id,
+ struct nvmet_rdma_queue *queue)
+{
+ unsigned long flags;
+
+ if (!queue) {
+ struct nvmet_port *port = cm_id->context;
+
+ /*
+ * This is a listener cm_id. Make sure that
+ * future remove_port won't invoke a double
+ * cm_id destroy. use atomic xchg to make sure
+ * we don't compete with remove_port.
+ */
+ if (xchg(&port->priv, NULL) != cm_id)
+ return 0;
+ } else {
+ /*
+ * This is a queue cm_id. Make sure that
+ * release queue will not destroy the cm_id
+ * and schedule all ctrl queues removal (only
+ * if the queue is not disconnecting already).
+ */
+ spin_lock_irqsave(&queue->state_lock, flags);
+ if (queue->state != NVMET_RDMA_Q_DISCONNECTING)
+ queue->state = NVMET_RDMA_IN_DEVICE_REMOVAL;
+ spin_unlock_irqrestore(&queue->state_lock, flags);
+ nvmet_rdma_queue_disconnect(queue);
+ flush_scheduled_work();
+ }
+
+ /*
+ * We need to return 1 so that the core will destroy
+ * it's own ID. What a great API design..
+ */
+ return 1;
+}
+
static int nvmet_rdma_cm_handler(struct rdma_cm_id *cm_id,
struct rdma_cm_event *event)
{
@@ -1294,20 +1355,11 @@
break;
case RDMA_CM_EVENT_ADDR_CHANGE:
case RDMA_CM_EVENT_DISCONNECTED:
- case RDMA_CM_EVENT_DEVICE_REMOVAL:
case RDMA_CM_EVENT_TIMEWAIT_EXIT:
- /*
- * We can get the device removal callback even for a
- * CM ID that we aren't actually using. In that case
- * the context pointer is NULL, so we shouldn't try
- * to disconnect a non-existing queue. But we also
- * need to return 1 so that the core will destroy
- * it's own ID. What a great API design..
- */
- if (queue)
- nvmet_rdma_queue_disconnect(queue);
- else
- ret = 1;
+ nvmet_rdma_queue_disconnect(queue);
+ break;
+ case RDMA_CM_EVENT_DEVICE_REMOVAL:
+ ret = nvmet_rdma_device_removal(cm_id, queue);
break;
case RDMA_CM_EVENT_REJECTED:
case RDMA_CM_EVENT_UNREACHABLE:
@@ -1396,9 +1448,10 @@
static void nvmet_rdma_remove_port(struct nvmet_port *port)
{
- struct rdma_cm_id *cm_id = port->priv;
+ struct rdma_cm_id *cm_id = xchg(&port->priv, NULL);
- rdma_destroy_id(cm_id);
+ if (cm_id)
+ rdma_destroy_id(cm_id);
}
static struct nvmet_fabrics_ops nvmet_rdma_ops = {