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, 8 insertions, 2 deletions

diff --git a/net/9p/client.c b/net/9p/client.c
index 2ffe40cf2f01..10e320307ec0 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -75,7 +75,6 @@ static int parse_opts(char *opts, struct p9_client *clnt)
         int option;
         int ret = 0;
 
-        clnt->trans_mod = v9fs_default_trans();
         clnt->dotu = 1;
         clnt->msize = 8192;
 
@@ -108,7 +107,7 @@ static int parse_opts(char *opts, struct p9_client *clnt)
                         clnt->msize = option;
                         break;
                 case Opt_trans:
-                        clnt->trans_mod = v9fs_match_trans(&args[0]);
+                        clnt->trans_mod = v9fs_get_trans_by_name(&args[0]);
                         break;
                 case Opt_legacy:
                         clnt->dotu = 0;
@@ -117,6 +116,10 @@ static int parse_opts(char *opts, struct p9_client *clnt)
                         continue;
                 }
         }
+
+        if (!clnt->trans_mod)
+                clnt->trans_mod = v9fs_get_default_trans();
+
         kfree(options);
         return ret;
 }
@@ -150,6 +153,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
         if (!clnt)
                 return ERR_PTR(-ENOMEM);
 
+        clnt->trans_mod = NULL;
         clnt->trans = NULL;
         spin_lock_init(&clnt->lock);
         INIT_LIST_HEAD(&clnt->fidlist);
@@ -235,6 +239,8 @@ void p9_client_destroy(struct p9_client *clnt)
                 clnt->trans = NULL;
         }
 
+        v9fs_put_trans(clnt->trans_mod);
+
         list_for_each_entry_safe(fid, fidptr, &clnt->fidlist, flist)
                 p9_fid_destroy(fid);