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, 1 insertions, 0 deletions

diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index b3d3e27c6299..c3626c0ba9d3 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -596,4 +596,5 @@ int p9_idpool_check(int id, struct p9_idpool *p);
 int p9_error_init(void);
 int p9_errstr2errno(char *, int);
 int p9_trans_fd_init(void);
+void p9_trans_fd_exit(void);
 #endif /* NET_9P_H */