Re: [PATCH v2 2/2] rdma: Autoload netlink client modules

If a message comes in and we do not have the client in the table, then
try to load the module supplying that client using MODULE_ALIAS to find
it.

This duplicates the scheme seen in other netlink muxes (eg nfnetlink).

Signed-off-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
---
 drivers/infiniband/core/cma.c     |  2 ++
 drivers/infiniband/core/device.c  |  2 ++
 drivers/infiniband/core/iwcm.c    |  2 ++
 drivers/infiniband/core/netlink.c |  9 +++++++++
 drivers/infiniband/core/nldev.c   |  3 +++
 include/rdma/rdma_netlink.h       | 12 ++++++++++++
 6 files changed, 30 insertions(+)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index d8edd8b11561ae..b76de2e2b20950 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c

@@ -4537,5 +4537,7 @@ static void __exit cma_cleanup(void)
 	destroy_workqueue(cma_wq);
 }

+MODULE_ALIAS_RDMA_NETLINK(RDMA_NL_RDMA_CM, 1);
+
 module_init(cma_init);
 module_exit(cma_cleanup);

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index fbc92c649be85d..5f9d4ae5eda8eb 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c

@@ -1251,5 +1251,7 @@ static void __exit ib_core_cleanup(void)
 	destroy_workqueue(ib_wq);
 }

+MODULE_ALIAS_RDMA_NETLINK(RDMA_NL_LS, 4);
+
 module_init(ib_core_init);
 module_exit(ib_core_cleanup);

diff --git a/drivers/infiniband/core/iwcm.c b/drivers/infiniband/core/iwcm.c
index 452a3115e3e6ba..af6015a7a8f361 100644
--- a/drivers/infiniband/core/iwcm.c
+++ b/drivers/infiniband/core/iwcm.c

@@ -1200,5 +1200,7 @@ static void __exit iw_cm_cleanup(void)
 	iwpm_exit(RDMA_NL_IWCM);
 }

+MODULE_ALIAS_RDMA_NETLINK(RDMA_NL_IWCM, 2);
+
 module_init(iw_cm_init);
 module_exit(iw_cm_cleanup);

diff --git a/drivers/infiniband/core/netlink.c b/drivers/infiniband/core/netlink.c
index f782697cf4d819..e685148dd3e6c2 100644
--- a/drivers/infiniband/core/netlink.c
+++ b/drivers/infiniband/core/netlink.c

@@ -84,6 +84,15 @@ static bool is_nl_valid(unsigned int type, unsigned int op)
 		return false;

 	cb_table = rdma_nl_types[type].cb_table;
+#ifdef CONFIG_MODULES
+	if (!cb_table) {
+		mutex_unlock(&rdma_nl_mutex);
+		request_module("rdma-netlink-subsys-%d", type);
+		mutex_lock(&rdma_nl_mutex);
+		cb_table = rdma_nl_types[type].cb_table;
+	}
+#endif
+
 	if (!cb_table || (!cb_table[op].dump && !cb_table[op].doit))
 		return false;
 	return true;

diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
index 474022274e09cd..3ba24c428c3bda 100644
--- a/drivers/infiniband/core/nldev.c
+++ b/drivers/infiniband/core/nldev.c

@@ -30,6 +30,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */

+#include <linux/module.h>
 #include <net/netlink.h>
 #include <rdma/rdma_netlink.h>

@@ -320,3 +321,5 @@ void __exit nldev_exit(void)
 {
 	rdma_nl_unregister(RDMA_NL_NLDEV);
 }
+
+MODULE_ALIAS_RDMA_NETLINK(RDMA_NL_NLDEV, 5);

diff --git a/include/rdma/rdma_netlink.h b/include/rdma/rdma_netlink.h
index e25bf1988846df..2d878596b1e07a 100644
--- a/include/rdma/rdma_netlink.h
+++ b/include/rdma/rdma_netlink.h

@@ -17,6 +17,18 @@ enum rdma_nl_flags {
 	RDMA_NL_ADMIN_PERM	= 1 << 0,
 };

+/* Define this module as providing netlink services for NETLINK_RDMA, with
+ * index _index.  Since the client indexes were setup in a uapi header as an
+ * enum and we do no want to change that, the user must supply the expanded
+ * constant as well and the compiler checks they are the same.
+ */
+#define MODULE_ALIAS_RDMA_NETLINK(_index, _val)                                \
+	static inline void __chk_##_index(void)                                \
+	{                                                                      \
+		BUILD_BUG_ON(_index != _val);                                  \
+	}                                                                      \
+	MODULE_ALIAS("rdma-netlink-subsys-" __stringify(_val))
+