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author | Tejun Heo <tj@kernel.org> | 2008-09-24 16:22:23 -0500 |
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committer | Eric Van Hensbergen <ericvh@ericvh-desktop.austin.ibm.com> | 2008-09-24 16:22:23 -0500 |
commit | 72029fe85d8d060b3f966f2dbc36b3c75b5a6532 (patch) | |
tree | ef8948240b0aff2a366136a8303afc70e6c84da8 /net/9p/mod.c | |
parent | 72d31053f62c4bc464c2783974926969614a8649 (diff) | |
download | lwn-72029fe85d8d060b3f966f2dbc36b3c75b5a6532.tar.gz lwn-72029fe85d8d060b3f966f2dbc36b3c75b5a6532.zip |
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.c | 92 |
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) |