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9p: implement proper trans module refcounting and unregistration

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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>
This commit is contained in:
Tejun Heo 2008-09-24 16:22:23 -05:00 • committed by Eric Van Hensbergen
parent 72d31053f6
commit 72029fe85d
6 changed files with 95 additions and 30 deletions
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92
net/9p/mod.c
View file

@ -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;
struct p9_trans_module *t, *found = 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;
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;
}
EXPORT_SYMBOL(v9fs_default_trans);
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_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)