[PATCH] IB/cm: drop REQ when out of memory

[Michael S. Tsirkin]

Hello Andrew!
Could you please drop the following in -mm and on to Linus?

---

If a user of the IB CM returns -ENOMEM from their connection callback,
simply drop the incoming REQ - do not attempt to send a reject. This should
allow the sender to retry the request.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxxxxxx>
Signed-off-by: Sean Hefty <sean.hefty@xxxxxxxxx>

Index: l/drivers/infiniband/core/cm.c
===================================================================
--- l/drivers/infiniband/core/cm.c	(revision 8224)
+++ l/drivers/infiniband/core/cm.c	(working copy)
@@ -702,7 +702,7 @@ static void cm_reset_to_idle(struct cm_i
 	}
 }
 
-void ib_destroy_cm_id(struct ib_cm_id *cm_id)
+static void cm_destroy_id(struct ib_cm_id *cm_id, int err)
 {
 	struct cm_id_private *cm_id_priv;
 	struct cm_work *work;
@@ -736,12 +736,22 @@ retest:
 			       sizeof cm_id_priv->av.port->cm_dev->ca_guid,
 			       NULL, 0);
 		break;
+	case IB_CM_REQ_RCVD:
+		if (err == -ENOMEM) {
+			/* Do not reject to allow future retries. */
+			cm_reset_to_idle(cm_id_priv);
+			spin_unlock_irqrestore(&cm_id_priv->lock, flags);
+		} else {
+			spin_unlock_irqrestore(&cm_id_priv->lock, flags);
+			ib_send_cm_rej(cm_id, IB_CM_REJ_CONSUMER_DEFINED,
+				       NULL, 0, NULL, 0);
+		}
+		break;
 	case IB_CM_MRA_REQ_RCVD:
 	case IB_CM_REP_SENT:
 	case IB_CM_MRA_REP_RCVD:
 		ib_cancel_mad(cm_id_priv->av.port->mad_agent, cm_id_priv->msg);
 		/* Fall through */
-	case IB_CM_REQ_RCVD:
 	case IB_CM_MRA_REQ_SENT:
 	case IB_CM_REP_RCVD:
 	case IB_CM_MRA_REP_SENT:
@@ -776,6 +786,11 @@ retest:
 	kfree(cm_id_priv->private_data);
 	kfree(cm_id_priv);
 }
+
+void ib_destroy_cm_id(struct ib_cm_id *cm_id)
+{
+	cm_destroy_id(cm_id, 0);
+}
 EXPORT_SYMBOL(ib_destroy_cm_id);
 
 int ib_cm_listen(struct ib_cm_id *cm_id, __be64 service_id, __be64 service_mask,
@@ -1164,7 +1179,7 @@ static void cm_process_work(struct cm_id
 	}
 	cm_deref_id(cm_id_priv);
 	if (ret)
-		ib_destroy_cm_id(&cm_id_priv->id);
+		cm_destroy_id(&cm_id_priv->id, ret);
 }
 
 static void cm_format_mra(struct cm_mra_msg *mra_msg,

-- 
MST

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-- 
MST
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