[PATCH v3 01/12] net: qrtr: support getting new endpoint ids externally

[Juha-Matti Tilli]

This is originally based on a patch by Mihai Moldovan, that allowed
registering endpoint-specific data and getting endpoint ids by the
endpoint-specific data. Unfortunately, the old API did not support
freeing the ids, creating a memory leak if someone repeatedly unloads
and reloads kernel modules. Also, the old API had O(N) complexity where
N was the amount of leaked memory. Because the patch has been
extensively changed, I reset authorship.

So, the new patch version only supports getting ids externally, with the
idea being that MHI controller would know about its endpoint id.

I made sure getting new data ids is permissible while holding a
spinlock, since multiple threads may race to get the same id.

Originally-by: Mihai Moldovan <ionic at ionic.de>
Signed-off-by: Mihai Moldovan <ionic at ionic.de>
Signed-off-by: Juha-Matti Tilli <juha-matti.tilli at iki.fi>
---
 MAINTAINERS        |  1 +
 include/net/qrtr.h | 10 ++++++++++
 net/qrtr/af_qrtr.c | 42 ++++++++++++++++++++++++++++++++++++------
 net/qrtr/qrtr.h    |  5 +++++
 4 files changed, 52 insertions(+), 6 deletions(-)
 create mode 100644 include/net/qrtr.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 0b42e898f4d8e..491f09cb7939c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22506,6 +22506,7 @@ QUALCOMM IPC ROUTER (QRTR) DRIVER
 M:	Manivannan Sadhasivam <mani at kernel.org>
 L:	linux-arm-msm at vger.kernel.org
 S:	Maintained
+F:	include/net/qrtr.h
 F:	include/trace/events/qrtr.h
 F:	include/uapi/linux/qrtr.h
 F:	net/qrtr/
diff --git a/include/net/qrtr.h b/include/net/qrtr.h
new file mode 100644
index 0000000000000..762d60b03012e
--- /dev/null
+++ b/include/net/qrtr.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __NET_QRTR_H
+#define __NET_QRTR_H
+
+#include <linux/types.h>
+
+int qrtr_endpoint_get_data_id(u32 *endpoint_id);
+void qrtr_endpoint_free_data_id(u32 endpoint_id);
+
+#endif	/* __NET_QRTR_H */
diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
index 7c50d32b11015..86a92e95e270f 100644
--- a/net/qrtr/af_qrtr.c
+++ b/net/qrtr/af_qrtr.c
@@ -11,6 +11,7 @@
 #include <linux/wait.h>
 
 #include <net/sock.h>
+#include <net/qrtr.h>
 
 #include "qrtr.h"
 
@@ -753,8 +754,8 @@ static struct sk_buff *qrtr_alloc_ctrl_packet(struct qrtr_ctrl_pkt **pkt,
 int qrtr_endpoint_register(struct qrtr_endpoint *ep, unsigned int nid)
 {
 	struct qrtr_node *node;
-	u32 endpoint_id;
-	int rc;
+	u32 endpoint_id = 0;
+	int rc = 0;
 
 	if (!ep || !ep->xmit)
 		return -EINVAL;
@@ -763,9 +764,18 @@ int qrtr_endpoint_register(struct qrtr_endpoint *ep, unsigned int nid)
 	if (!node)
 		return -ENOMEM;
 
-	rc = xa_alloc_cyclic(&qrtr_endpoints, &endpoint_id, NULL,
-			     QRTR_ENDPOINT_RANGE, &next_endpoint_id,
-			     GFP_KERNEL);
+	if (ep->endpoint_data_id)
+		endpoint_id = ep->endpoint_data_id;
+
+	/*
+	 * If we're registering an endpoint into smd or tun based qrtr,
+	 * we don't have endpoint_data_id. Thus, allocate a new one.
+	 */
+	if (!endpoint_id) {
+		rc = xa_alloc_cyclic(&qrtr_endpoints, &endpoint_id, NULL,
+				     QRTR_ENDPOINT_RANGE, &next_endpoint_id,
+				     GFP_KERNEL);
+	}
 
 	if (rc < 0)
 		goto free_node;
@@ -857,13 +867,33 @@ void qrtr_endpoint_unregister(struct qrtr_endpoint *ep)
 
 	qrtr_node_release(node);
 
-	xa_erase(&qrtr_endpoints, endpoint_id);
+	if (ep->endpoint_data_id != endpoint_id)
+		xa_erase(&qrtr_endpoints, endpoint_id); // did allocate
 
 	ep->id = 0;
 	ep->node = NULL;
 }
 EXPORT_SYMBOL_GPL(qrtr_endpoint_unregister);
 
+int qrtr_endpoint_get_data_id(u32 *endpoint_id)
+{
+	int rc;
+
+	*endpoint_id = 0;
+	// GFP_ATOMIC to allow while holding spinlock
+	rc = xa_alloc_cyclic(&qrtr_endpoints, endpoint_id, NULL,
+			     QRTR_ENDPOINT_RANGE, &next_endpoint_id,
+			     GFP_ATOMIC);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(qrtr_endpoint_get_data_id);
+
+void qrtr_endpoint_free_data_id(u32 endpoint_id)
+{
+	xa_erase(&qrtr_endpoints, endpoint_id);
+}
+EXPORT_SYMBOL_GPL(qrtr_endpoint_free_data_id);
+
 /* Lookup socket by port.
  *
  * Callers must release with qrtr_port_put()
diff --git a/net/qrtr/qrtr.h b/net/qrtr/qrtr.h
index affc24f426c64..86c9b4e724d7e 100644
--- a/net/qrtr/qrtr.h
+++ b/net/qrtr/qrtr.h
@@ -21,6 +21,7 @@ struct qrtr_node_lookup_helper {
 /**
  * struct qrtr_endpoint - endpoint handle
  * @xmit: Callback for outgoing packets
+ * @endpoint_data_id: an already allocated id to be used instead of new alloc
  *
  * The socket buffer passed to the xmit function becomes owned by the endpoint
  * driver.  As such, when the driver is done with the buffer, it should
@@ -32,6 +33,7 @@ struct qrtr_endpoint {
 	struct qrtr_node *node;
 	struct qrtr_node_lookup_helper helper;
 	u32 id;
+	u32 endpoint_data_id;
 };
 
 int qrtr_endpoint_register(struct qrtr_endpoint *ep, unsigned int nid);
@@ -47,4 +49,7 @@ void qrtr_ns_remove(void);
 int qrtr_msg_get_endpoint(struct msghdr *msg, u32 *out_endpoint_id);
 void qrtr_sock_set_report_endpoint(struct sock *sk);
 
+int qrtr_endpoint_get_data_id(u32 *endpoint_id);
+void qrtr_endpoint_free_data_id(u32 endpoint_id);
+
 #endif
-- 
2.34.1