dm log: auto load modules

If the log type is not recognised, attempt to load the module
'dm-log-<type>.ko'.

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

1 files changed, 50 insertions, 1 deletions

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 072ee4353eab..2a74b2142f50 100644
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -41,7 +41,7 @@ int dm_unregister_dirty_log_type(struct dirty_log_type *type)
         return 0;
 }
 
-static struct dirty_log_type *get_type(const char *type_name)
+static struct dirty_log_type *_get_type(const char *type_name)
 {
         struct dirty_log_type *type;
 
@@ -61,6 +61,55 @@ static struct dirty_log_type *get_type(const char *type_name)
         return NULL;
 }
 
+/*
+ * get_type
+ * @type_name
+ *
+ * Attempt to retrieve the 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'.
+ * Modules may contain multiple types.
+ * This function will first try the module "dm-log-<type_name>",
+ * then truncate 'type_name' on the last '-' and try again.
+ *
+ * For example, if type_name was "clustered-disk", it would search
+ * 'dm-log-clustered-disk' then 'dm-log-clustered'.
+ *
+ * Returns: dirty_log_type* on success, NULL on failure
+ */
+static struct dirty_log_type *get_type(const char *type_name)
+{
+        char *p, *type_name_dup;
+        struct dirty_log_type *type;
+
+        type = _get_type(type_name);
+        if (type)
+                return type;
+
+        type_name_dup = kstrdup(type_name, GFP_KERNEL);
+        if (!type_name_dup) {
+                DMWARN("No memory left to attempt log module load for \"%s\"",
+                       type_name);
+                return NULL;
+        }
+
+        while (request_module("dm-log-%s", type_name_dup) ||
+               !(type = _get_type(type_name))) {
+                p = strrchr(type_name_dup, '-');
+                if (!p)
+                        break;
+                p[0] = '\0';
+        }
+
+        if (!type)
+                DMWARN("Module for logging type \"%s\" not found.", type_name);
+
+        kfree(type_name_dup);
+
+        return type;
+}
+
 static void put_type(struct dirty_log_type *type)
 {
         spin_lock(&_lock);