net: qrtr: Add backup skb pool

Add a pool of SKBs that can be used when the system is in low memory
conditions. This pool will be shared between all nodes and replenished
by a worker function.

Change-Id: I639a9ac76db726dc8ad46b12d3b3d560c674939c
Signed-off-by: Chris Lew <clew@codeaurora.org>
Signed-off-by: Vivek Golani <vgolani@codeaurora.org>

net/qrtr/qrtr.c

@@ -135,6 +135,15 @@ static DECLARE_RWSEM(qrtr_node_lock);
 static DEFINE_IDR(qrtr_ports);
 static DEFINE_MUTEX(qrtr_port_lock);
 
+/* backup buffers */
+#define QRTR_BACKUP_HI_NUM	5
+#define QRTR_BACKUP_HI_SIZE	SZ_16K
+#define QRTR_BACKUP_LO_NUM	20
+#define QRTR_BACKUP_LO_SIZE	SZ_1K
+static struct sk_buff_head qrtr_backup_lo;
+static struct sk_buff_head qrtr_backup_hi;
+static struct work_struct qrtr_backup_work;
+
 /**
  * struct qrtr_node - endpoint node
  * @ep_lock: lock for endpoint management and callbacks
@@ -694,6 +703,54 @@ int qrtr_peek_pkt_size(const void *data)
 }
 EXPORT_SYMBOL(qrtr_peek_pkt_size);
 
+static void qrtr_alloc_backup(struct work_struct *work)
+{
+	struct sk_buff *skb;
+
+	while (skb_queue_len(&qrtr_backup_lo) < QRTR_BACKUP_LO_NUM) {
+		skb = alloc_skb(QRTR_BACKUP_LO_SIZE, GFP_KERNEL);
+		if (!skb)
+			break;
+		skb_queue_tail(&qrtr_backup_lo, skb);
+	}
+	while (skb_queue_len(&qrtr_backup_hi) < QRTR_BACKUP_HI_NUM) {
+		skb = alloc_skb(QRTR_BACKUP_HI_SIZE, GFP_KERNEL);
+		if (!skb)
+			break;
+		skb_queue_tail(&qrtr_backup_hi, skb);
+	}
+}
+
+static struct sk_buff *qrtr_get_backup(size_t len)
+{
+	struct sk_buff *skb = NULL;
+
+	if (len < QRTR_BACKUP_LO_SIZE)
+		skb = skb_dequeue(&qrtr_backup_lo);
+	else if (len < QRTR_BACKUP_HI_SIZE)
+		skb = skb_dequeue(&qrtr_backup_hi);
+
+	if (skb)
+		queue_work(system_unbound_wq, &qrtr_backup_work);
+
+	return skb;
+}
+
+static void qrtr_backup_init(void)
+{
+	skb_queue_head_init(&qrtr_backup_lo);
+	skb_queue_head_init(&qrtr_backup_hi);
+	INIT_WORK(&qrtr_backup_work, qrtr_alloc_backup);
+	queue_work(system_unbound_wq, &qrtr_backup_work);
+}
+
+static void qrtr_backup_deinit(void)
+{
+	cancel_work_sync(&qrtr_backup_work);
+	skb_queue_purge(&qrtr_backup_lo);
+	skb_queue_purge(&qrtr_backup_hi);
+}
+
 /**
  * qrtr_endpoint_post() - post incoming data
  * @ep: endpoint handle
@@ -718,8 +775,13 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)
 		return -EINVAL;
 
 	skb = alloc_skb_with_frags(sizeof(*v1), len, 0, &errcode, GFP_ATOMIC);
-	if (!skb)
-		return -ENOMEM;
+	if (!skb) {
+		skb = qrtr_get_backup(len);
+		if (!skb) {
+			pr_err("qrtr: Unable to get skb with len:%lu\n", len);
+			return -ENOMEM;
+		}
+	}
 
 	skb_reserve(skb, sizeof(*v1));
 	cb = (struct qrtr_cb *)skb->cb;
@@ -1951,7 +2013,10 @@ static int __init qrtr_proto_init(void)
 
 	rtnl_register(PF_QIPCRTR, RTM_NEWADDR, qrtr_addr_doit, NULL, 0);
 
+	qrtr_backup_init();
+
 	return 0;
+
 }
 postcore_initcall(qrtr_proto_init);
 
@@ -1960,6 +2025,8 @@ static void __exit qrtr_proto_fini(void)
 	rtnl_unregister(PF_QIPCRTR, RTM_NEWADDR);
 	sock_unregister(qrtr_family.family);
 	proto_unregister(&qrtr_proto);
+
+	qrtr_backup_deinit();
 }
 module_exit(qrtr_proto_fini);