dm log: make module use tracking internal

Remove internal module reference fields from the interface.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

2 files changed, 94 insertions, 31 deletions

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 82df73f67a0d..e6b6a9d5fdd2 100644
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -16,34 +16,51 @@
 
 #define DM_MSG_PREFIX "dirty region log"
 
+struct dm_dirty_log_internal {
+        struct dm_dirty_log_type *type;
+
+        struct list_head list;
+        long use;
+};
+
 static LIST_HEAD(_log_types);
 static DEFINE_SPINLOCK(_lock);
 
-static struct dm_dirty_log_type *_get_type(const char *type_name)
+static struct dm_dirty_log_internal *__find_dirty_log_type(const char *name)
 {
-        struct dm_dirty_log_type *type;
+        struct dm_dirty_log_internal *log_type;
+
+        list_for_each_entry(log_type, &_log_types, list)
+                if (!strcmp(name, log_type->type->name))
+                        return log_type;
+
+        return NULL;
+}
+
+static struct dm_dirty_log_internal *_get_dirty_log_type(const char *name)
+{
+        struct dm_dirty_log_internal *log_type;
 
         spin_lock(&_lock);
-        list_for_each_entry (type, &_log_types, list)
-                if (!strcmp(type_name, type->name)) {
-                        if (!type->use_count && !try_module_get(type->module)){
-                                spin_unlock(&_lock);
-                                return NULL;
-                        }
-                        type->use_count++;
-                        spin_unlock(&_lock);
-                        return type;
-                }
+
+        log_type = __find_dirty_log_type(name);
+        if (log_type) {
+                if (!log_type->use && !try_module_get(log_type->type->module))
+                        log_type = NULL;
+                else
+                        log_type->use++;
+        }
 
         spin_unlock(&_lock);
-        return NULL;
+
+        return log_type;
 }
 
 /*
  * get_type
  * @type_name
  *
- * Attempt to retrieve the dirty_log_type by name.  If not already
+ * Attempt to retrieve the dm_dirty_log_type by name.  If not already
  * available, attempt to load the appropriate module.
  *
  * Log modules are named "dm-log-" followed by the 'type_name'.
@@ -59,11 +76,14 @@ static struct dm_dirty_log_type *_get_type(const char *type_name)
 static struct dm_dirty_log_type *get_type(const char *type_name)
 {
         char *p, *type_name_dup;
-        struct dm_dirty_log_type *type;
+        struct dm_dirty_log_internal *log_type;
 
-        type = _get_type(type_name);
-        if (type)
-                return type;
+        if (!type_name)
+                return NULL;
+
+        log_type = _get_dirty_log_type(type_name);
+        if (log_type)
+                return log_type->type;
 
         type_name_dup = kstrdup(type_name, GFP_KERNEL);
         if (!type_name_dup) {
@@ -73,50 +93,95 @@ static struct dm_dirty_log_type *get_type(const char *type_name)
         }
 
         while (request_module("dm-log-%s", type_name_dup) ||
-               !(type = _get_type(type_name))) {
+               !(log_type = _get_dirty_log_type(type_name))) {
                 p = strrchr(type_name_dup, '-');
                 if (!p)
                         break;
                 p[0] = '\0';
         }
 
-        if (!type)
+        if (!log_type)
                 DMWARN("Module for logging type \"%s\" not found.", type_name);
 
         kfree(type_name_dup);
 
-        return type;
+        return log_type ? log_type->type : NULL;
 }
 
 static void put_type(struct dm_dirty_log_type *type)
 {
+        struct dm_dirty_log_internal *log_type;
+
+        if (!type)
+                return;
+
         spin_lock(&_lock);
-        if (!--type->use_count)
+        log_type = __find_dirty_log_type(type->name);
+        if (!log_type)
+                goto out;
+
+        if (!--log_type->use)
                 module_put(type->module);
+
+        BUG_ON(log_type->use < 0);
+
+out:
         spin_unlock(&_lock);
 }
 
+static struct dm_dirty_log_internal *_alloc_dirty_log_type(struct dm_dirty_log_type *type)
+{
+        struct dm_dirty_log_internal *log_type = kzalloc(sizeof(*log_type),
+                                                         GFP_KERNEL);
+
+        if (log_type)
+                log_type->type = type;
+
+        return log_type;
+}
+
 int dm_dirty_log_type_register(struct dm_dirty_log_type *type)
 {
+        struct dm_dirty_log_internal *log_type = _alloc_dirty_log_type(type);
+        int r = 0;
+
+        if (!log_type)
+                return -ENOMEM;
+
         spin_lock(&_lock);
-        type->use_count = 0;
-        list_add(&type->list, &_log_types);
+        if (!__find_dirty_log_type(type->name))
+                list_add(&log_type->list, &_log_types);
+        else {
+                kfree(log_type);
+                r = -EEXIST;
+        }
         spin_unlock(&_lock);
 
-        return 0;
+        return r;
 }
 EXPORT_SYMBOL(dm_dirty_log_type_register);
 
 int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type)
 {
+        struct dm_dirty_log_internal *log_type;
+
         spin_lock(&_lock);
 
-        if (type->use_count)
-                DMWARN("Attempt to unregister a log type that is still in use");
-        else
-                list_del(&type->list);
+        log_type = __find_dirty_log_type(type->name);
+        if (!log_type) {
+                spin_unlock(&_lock);
+                return -EINVAL;
+        }
+
+        if (log_type->use) {
+                spin_unlock(&_lock);
+                return -ETXTBSY;
+        }
+
+        list_del(&log_type->list);
 
         spin_unlock(&_lock);
+        kfree(log_type);
 
         return 0;
 }
diff --git a/drivers/md/dm-log.h b/drivers/md/dm-log.h
index 2da48a857cb9..600c5fb2daad 100644
--- a/drivers/md/dm-log.h
+++ b/drivers/md/dm-log.h
@@ -25,10 +25,8 @@ struct dm_dirty_log {
 };
 
 struct dm_dirty_log_type {
-        struct list_head list;
         const char *name;
         struct module *module;
-        unsigned use_count;
 
         int (*ctr)(struct dm_dirty_log *log, struct dm_target *ti,
                    unsigned argc, char **argv);