9p: implement proper trans module refcounting and unregistration

9p trans modules aren't refcounted nor were they unregistered
properly.  Fix it.

* Add 9p_trans_module->owner and reference the module on each trans
  instance creation and put it on destruction.

* Protect v9fs_trans_list with a spinlock.  This isn't strictly
  necessary as the list is manipulated only during module loading /
  unloading but it's a good idea to make the API safe.

* Unregister trans modules when the corresponding module is being
  unloaded.

* While at it, kill unnecessary EXPORT_SYMBOL on p9_trans_fd_init().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index cdf137af7adc..6a32ffdb9429 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -1629,6 +1629,7 @@ static struct p9_trans_module p9_tcp_trans = {
         .maxsize = MAX_SOCK_BUF,
         .def = 1,
         .create = p9_trans_create_tcp,
+        .owner = THIS_MODULE,
 };
 
 static struct p9_trans_module p9_unix_trans = {
@@ -1636,6 +1637,7 @@ static struct p9_trans_module p9_unix_trans = {
         .maxsize = MAX_SOCK_BUF,
         .def = 0,
         .create = p9_trans_create_unix,
+        .owner = THIS_MODULE,
 };
 
 static struct p9_trans_module p9_fd_trans = {
@@ -1643,6 +1645,7 @@ static struct p9_trans_module p9_fd_trans = {
         .maxsize = MAX_SOCK_BUF,
         .def = 0,
         .create = p9_trans_create_fd,
+        .owner = THIS_MODULE,
 };
 
 int p9_trans_fd_init(void)
@@ -1659,4 +1662,10 @@ int p9_trans_fd_init(void)
 
         return 0;
 }
-EXPORT_SYMBOL(p9_trans_fd_init);
+
+void p9_trans_fd_exit(void)
+{
+        v9fs_unregister_trans(&p9_tcp_trans);
+        v9fs_unregister_trans(&p9_unix_trans);
+        v9fs_unregister_trans(&p9_fd_trans);
+}