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authorTejun Heo <tj@kernel.org>2008-09-24 16:22:23 -0500
committerEric Van Hensbergen <ericvh@ericvh-desktop.austin.ibm.com>2008-09-24 16:22:23 -0500
commit72029fe85d8d060b3f966f2dbc36b3c75b5a6532 (patch)
treeef8948240b0aff2a366136a8303afc70e6c84da8 /net/9p/mod.c
parent72d31053f62c4bc464c2783974926969614a8649 (diff)
downloadlinux-72029fe85d8d060b3f966f2dbc36b3c75b5a6532.tar.bz2
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>
Diffstat (limited to 'net/9p/mod.c')
-rw-r--r--net/9p/mod.c92
1 files changed, 67 insertions, 25 deletions
diff --git a/net/9p/mod.c b/net/9p/mod.c
index bdee1fb7cc62..1084feb24cb0 100644
--- a/net/9p/mod.c
+++ b/net/9p/mod.c
@@ -31,6 +31,7 @@
#include <linux/parser.h>
#include <net/9p/transport.h>
#include <linux/list.h>
+#include <linux/spinlock.h>
#ifdef CONFIG_NET_9P_DEBUG
unsigned int p9_debug_level = 0; /* feature-rific global debug level */
@@ -44,8 +45,8 @@ MODULE_PARM_DESC(debug, "9P debugging level");
*
*/
+static DEFINE_SPINLOCK(v9fs_trans_lock);
static LIST_HEAD(v9fs_trans_list);
-static struct p9_trans_module *v9fs_default_transport;
/**
* v9fs_register_trans - register a new transport with 9p
@@ -54,48 +55,87 @@ static struct p9_trans_module *v9fs_default_transport;
*/
void v9fs_register_trans(struct p9_trans_module *m)
{
+ spin_lock(&v9fs_trans_lock);
list_add_tail(&m->list, &v9fs_trans_list);
- if (m->def)
- v9fs_default_transport = m;
+ spin_unlock(&v9fs_trans_lock);
}
EXPORT_SYMBOL(v9fs_register_trans);
/**
- * v9fs_match_trans - match transport versus registered transports
+ * v9fs_unregister_trans - unregister a 9p transport
+ * @m: the transport to remove
+ *
+ */
+void v9fs_unregister_trans(struct p9_trans_module *m)
+{
+ spin_lock(&v9fs_trans_lock);
+ list_del_init(&m->list);
+ spin_unlock(&v9fs_trans_lock);
+}
+EXPORT_SYMBOL(v9fs_unregister_trans);
+
+/**
+ * v9fs_get_trans_by_name - get transport with the matching name
* @name: string identifying transport
*
*/
-struct p9_trans_module *v9fs_match_trans(const substring_t *name)
+struct p9_trans_module *v9fs_get_trans_by_name(const substring_t *name)
{
- struct list_head *p;
- struct p9_trans_module *t = NULL;
-
- list_for_each(p, &v9fs_trans_list) {
- t = list_entry(p, struct p9_trans_module, list);
- if (strncmp(t->name, name->from, name->to-name->from) == 0)
- return t;
- }
- return NULL;
+ struct p9_trans_module *t, *found = NULL;
+
+ spin_lock(&v9fs_trans_lock);
+
+ list_for_each_entry(t, &v9fs_trans_list, list)
+ if (strncmp(t->name, name->from, name->to-name->from) == 0 &&
+ try_module_get(t->owner)) {
+ found = t;
+ break;
+ }
+
+ spin_unlock(&v9fs_trans_lock);
+ return found;
}
-EXPORT_SYMBOL(v9fs_match_trans);
+EXPORT_SYMBOL(v9fs_get_trans_by_name);
/**
- * v9fs_default_trans - returns pointer to default transport
+ * v9fs_get_default_trans - get the default transport
*
*/
-struct p9_trans_module *v9fs_default_trans(void)
+struct p9_trans_module *v9fs_get_default_trans(void)
{
- if (v9fs_default_transport)
- return v9fs_default_transport;
- else if (!list_empty(&v9fs_trans_list))
- return list_first_entry(&v9fs_trans_list,
- struct p9_trans_module, list);
- else
- return NULL;
+ struct p9_trans_module *t, *found = NULL;
+
+ spin_lock(&v9fs_trans_lock);
+
+ list_for_each_entry(t, &v9fs_trans_list, list)
+ if (t->def && try_module_get(t->owner)) {
+ found = t;
+ break;
+ }
+
+ if (!found)
+ list_for_each_entry(t, &v9fs_trans_list, list)
+ if (try_module_get(t->owner)) {
+ found = t;
+ break;
+ }
+
+ spin_unlock(&v9fs_trans_lock);
+ return found;
}
-EXPORT_SYMBOL(v9fs_default_trans);
+EXPORT_SYMBOL(v9fs_get_default_trans);
+/**
+ * v9fs_put_trans - put trans
+ * @m: transport to put
+ *
+ */
+void v9fs_put_trans(struct p9_trans_module *m)
+{
+ if (m)
+ module_put(m->owner);
+}
/**
* v9fs_init - Initialize module
@@ -120,6 +160,8 @@ static int __init init_p9(void)
static void __exit exit_p9(void)
{
printk(KERN_INFO "Unloading 9P2000 support\n");
+
+ p9_trans_fd_exit();
}
module_init(init_p9)