IB/iser: Simplify connection management
iSER relies on refcounting to manage iser connections establishment
and teardown.
Following commit 39ff05dbbbdb ("IB/iser: Enhance disconnection logic
for multi-pathing"), iser connection maintain 3 references:
- iscsi_endpoint (at creation stage)
- cma_id (at connection request stage)
- iscsi_conn (at bind stage)
We can avoid taking explicit refcounts by correctly serializing iser
teardown flows (graceful and non-graceful).
Our approach is to trigger a scheduled work to handle ordered teardown
by gracefully waiting for 2 cleanup stages to complete:
1. Cleanup of live pending tasks indicated by iscsi_conn_stop completion
2. Flush errors processing
Each completed stage will notify a waiting worker thread when it is
done to allow teardwon continuation.
Since iSCSI connection establishment may trigger endpoint disconnect
without a successful endpoint connect, we rely on the iscsi <-> iser
binding (.conn_bind) to learn about the teardown policy we should take
wrt cleanup stages.
Since all cleanup worker threads are scheduled (release_wq) in
.ep_disconnect it is safe to assume that when module_exit is called,
all cleanup workers are already scheduled. Thus proper module unload
shall flush all scheduled works before allowing safe exit, to
guarantee no resources got left behind.
Signed-off-by: Ariel Nahum <arieln@mellanox.com>
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.c b/drivers/infiniband/ulp/iser/iscsi_iser.c
index 25f195e..f217488 100644
--- a/drivers/infiniband/ulp/iser/iscsi_iser.c
+++ b/drivers/infiniband/ulp/iser/iscsi_iser.c
@@ -99,6 +99,7 @@
module_param_named(pi_guard, iser_pi_guard, int, 0644);
MODULE_PARM_DESC(pi_guard, "T10-PI guard_type, 0:CRC|1:IP_CSUM (default:CRC)");
+static struct workqueue_struct *release_wq;
struct iser_global ig;
void
@@ -337,24 +338,6 @@
return cls_conn;
}
-static void
-iscsi_iser_conn_destroy(struct iscsi_cls_conn *cls_conn)
-{
- struct iscsi_conn *conn = cls_conn->dd_data;
- struct iser_conn *ib_conn = conn->dd_data;
-
- iscsi_conn_teardown(cls_conn);
- /*
- * Userspace will normally call the stop callback and
- * already have freed the ib_conn, but if it goofed up then
- * we free it here.
- */
- if (ib_conn) {
- ib_conn->iscsi_conn = NULL;
- iser_conn_put(ib_conn, 1); /* deref iscsi/ib conn unbinding */
- }
-}
-
static int
iscsi_iser_conn_bind(struct iscsi_cls_session *cls_session,
struct iscsi_cls_conn *cls_conn, uint64_t transport_eph,
@@ -392,29 +375,39 @@
conn->dd_data = ib_conn;
ib_conn->iscsi_conn = conn;
- iser_conn_get(ib_conn); /* ref iscsi/ib conn binding */
return 0;
}
+static int
+iscsi_iser_conn_start(struct iscsi_cls_conn *cls_conn)
+{
+ struct iscsi_conn *iscsi_conn;
+ struct iser_conn *ib_conn;
+
+ iscsi_conn = cls_conn->dd_data;
+ ib_conn = iscsi_conn->dd_data;
+ reinit_completion(&ib_conn->stop_completion);
+
+ return iscsi_conn_start(cls_conn);
+}
+
static void
iscsi_iser_conn_stop(struct iscsi_cls_conn *cls_conn, int flag)
{
struct iscsi_conn *conn = cls_conn->dd_data;
struct iser_conn *ib_conn = conn->dd_data;
+ iser_dbg("stopping iscsi_conn: %p, ib_conn: %p\n", conn, ib_conn);
+ iscsi_conn_stop(cls_conn, flag);
+
/*
* Userspace may have goofed up and not bound the connection or
* might have only partially setup the connection.
*/
if (ib_conn) {
- iscsi_conn_stop(cls_conn, flag);
- /*
- * There is no unbind event so the stop callback
- * must release the ref from the bind.
- */
- iser_conn_put(ib_conn, 1); /* deref iscsi/ib conn unbinding */
+ conn->dd_data = NULL;
+ complete(&ib_conn->stop_completion);
}
- conn->dd_data = NULL;
}
static void iscsi_iser_session_destroy(struct iscsi_cls_session *cls_session)
@@ -652,19 +645,20 @@
struct iser_conn *ib_conn;
ib_conn = ep->dd_data;
- if (ib_conn->iscsi_conn)
- /*
- * Must suspend xmit path if the ep is bound to the
- * iscsi_conn, so we know we are not accessing the ib_conn
- * when we free it.
- *
- * This may not be bound if the ep poll failed.
- */
- iscsi_suspend_tx(ib_conn->iscsi_conn);
-
-
- iser_info("ib conn %p state %d\n", ib_conn, ib_conn->state);
+ iser_info("ep %p ib conn %p state %d\n", ep, ib_conn, ib_conn->state);
iser_conn_terminate(ib_conn);
+
+ /*
+ * if iser_conn and iscsi_conn are bound, we must wait iscsi_conn_stop
+ * call and ISER_CONN_DOWN state before freeing the iser resources.
+ * otherwise we are safe to free resources immediately.
+ */
+ if (ib_conn->iscsi_conn) {
+ INIT_WORK(&ib_conn->release_work, iser_release_work);
+ queue_work(release_wq, &ib_conn->release_work);
+ } else {
+ iser_conn_release(ib_conn);
+ }
}
static umode_t iser_attr_is_visible(int param_type, int param)
@@ -748,13 +742,13 @@
/* connection management */
.create_conn = iscsi_iser_conn_create,
.bind_conn = iscsi_iser_conn_bind,
- .destroy_conn = iscsi_iser_conn_destroy,
+ .destroy_conn = iscsi_conn_teardown,
.attr_is_visible = iser_attr_is_visible,
.set_param = iscsi_iser_set_param,
.get_conn_param = iscsi_conn_get_param,
.get_ep_param = iscsi_iser_get_ep_param,
.get_session_param = iscsi_session_get_param,
- .start_conn = iscsi_conn_start,
+ .start_conn = iscsi_iser_conn_start,
.stop_conn = iscsi_iser_conn_stop,
/* iscsi host params */
.get_host_param = iscsi_host_get_param,
@@ -801,6 +795,12 @@
mutex_init(&ig.connlist_mutex);
INIT_LIST_HEAD(&ig.connlist);
+ release_wq = alloc_workqueue("release workqueue", 0, 0);
+ if (!release_wq) {
+ iser_err("failed to allocate release workqueue\n");
+ return -ENOMEM;
+ }
+
iscsi_iser_scsi_transport = iscsi_register_transport(
&iscsi_iser_transport);
if (!iscsi_iser_scsi_transport) {
@@ -819,7 +819,24 @@
static void __exit iser_exit(void)
{
+ struct iser_conn *ib_conn, *n;
+ int connlist_empty;
+
iser_dbg("Removing iSER datamover...\n");
+ destroy_workqueue(release_wq);
+
+ mutex_lock(&ig.connlist_mutex);
+ connlist_empty = list_empty(&ig.connlist);
+ mutex_unlock(&ig.connlist_mutex);
+
+ if (!connlist_empty) {
+ iser_err("Error cleanup stage completed but we still have iser "
+ "connections, destroying them anyway.\n");
+ list_for_each_entry_safe(ib_conn, n, &ig.connlist, conn_list) {
+ iser_conn_release(ib_conn);
+ }
+ }
+
iscsi_unregister_transport(&iscsi_iser_transport);
kmem_cache_destroy(ig.desc_cache);
}