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>
diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index b3d3e27..c3626c0 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -596,4 +596,5 @@
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 */
diff --git a/include/net/9p/transport.h b/include/net/9p/transport.h
index 0db3a40..3ca7371 100644
--- a/include/net/9p/transport.h
+++ b/include/net/9p/transport.h
@@ -26,6 +26,8 @@
#ifndef NET_9P_TRANSPORT_H
#define NET_9P_TRANSPORT_H
+#include <linux/module.h>
+
/**
* enum p9_trans_status - different states of underlying transports
* @Connected: transport is connected and healthy
@@ -91,9 +93,12 @@
int maxsize; /* max message size of transport */
int def; /* this transport should be default */
struct p9_trans * (*create)(const char *, char *, int, unsigned char);
+ struct module *owner;
};
void v9fs_register_trans(struct p9_trans_module *m);
-struct p9_trans_module *v9fs_match_trans(const substring_t *name);
-struct p9_trans_module *v9fs_default_trans(void);
+void v9fs_unregister_trans(struct p9_trans_module *m);
+struct p9_trans_module *v9fs_get_trans_by_name(const substring_t *name);
+struct p9_trans_module *v9fs_get_default_trans(void);
+void v9fs_put_trans(struct p9_trans_module *m);
#endif /* NET_9P_TRANSPORT_H */
diff --git a/net/9p/client.c b/net/9p/client.c
index 2ffe40c..10e3203 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -75,7 +75,6 @@
int option;
int ret = 0;
- clnt->trans_mod = v9fs_default_trans();
clnt->dotu = 1;
clnt->msize = 8192;
@@ -108,7 +107,7 @@
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 @@
continue;
}
}
+
+ if (!clnt->trans_mod)
+ clnt->trans_mod = v9fs_get_default_trans();
+
kfree(options);
return ret;
}
@@ -150,6 +153,7 @@
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 @@
clnt->trans = NULL;
}
+ v9fs_put_trans(clnt->trans_mod);
+
list_for_each_entry_safe(fid, fidptr, &clnt->fidlist, flist)
p9_fid_destroy(fid);
diff --git a/net/9p/mod.c b/net/9p/mod.c
index bdee1fb..1084feb 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 @@
*
*/
+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 @@
*/
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 void __exit exit_p9(void)
{
printk(KERN_INFO "Unloading 9P2000 support\n");
+
+ p9_trans_fd_exit();
}
module_init(init_p9)
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index cdf137a..6a32ffd 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -1629,6 +1629,7 @@
.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 @@
.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 @@
.maxsize = MAX_SOCK_BUF,
.def = 0,
.create = p9_trans_create_fd,
+ .owner = THIS_MODULE,
};
int p9_trans_fd_init(void)
@@ -1659,4 +1662,10 @@
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);
+}
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 42adc05..94912e0 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -528,6 +528,7 @@
.create = p9_virtio_create,
.maxsize = PAGE_SIZE*16,
.def = 0,
+ .owner = THIS_MODULE,
};
/* The standard init function */
@@ -545,6 +546,7 @@
static void __exit p9_virtio_cleanup(void)
{
unregister_virtio_driver(&p9_virtio_drv);
+ v9fs_unregister_trans(&p9_virtio_trans);
}
module_init(p9_virtio_init);
