device-mapper: fix mirror log type module ref count

[Alasdair G Kergon]

Fix module reference counting for mirror log type.

Signed-Off-By: Alasdair G Kergon <[EMAIL PROTECTED]>
--- diff/drivers/md/dm-log.c    2005-01-12 15:21:22.000000000 +0000
+++ source/drivers/md/dm-log.c  2005-01-12 18:55:17.000000000 +0000
@@ -17,9 +17,6 @@
 
 int dm_register_dirty_log_type(struct dirty_log_type *type)
 {
-       if (!try_module_get(type->module))
-               return -EINVAL;
-
        spin_lock(&_lock);
        type->use_count = 0;
        list_add(&type->list, &_log_types);
@@ -34,10 +31,8 @@
 
        if (type->use_count)
                DMWARN("Attempt to unregister a log type that is still in use");
-       else {
+       else
                list_del(&type->list);
-               module_put(type->module);
-       }
 
        spin_unlock(&_lock);
 
@@ -51,6 +46,10 @@
        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;
@@ -63,7 +62,8 @@
 static void put_type(struct dirty_log_type *type)
 {
        spin_lock(&_lock);
-       type->use_count--;
+       if (!--type->use_count)
+               module_put(type->module);
        spin_unlock(&_lock);
 }
 
-
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