ocfs2: Break out stackglue into modules.

We define the ocfs2_stack_plugin structure to represent a stack driver.
The o2cb stack code is split into stack_o2cb.c.  This becomes the
ocfs2_stack_o2cb.ko module.

The stackglue generic functions are similarly split into the
ocfs2_stackglue.ko module.  This module now provides an interface to
register drivers.  The ocfs2_stack_o2cb driver registers itself.  As
part of this interface, ocfs2_stackglue can load drivers on demand.
This is accomplished in ocfs2_cluster_connect().

ocfs2_cluster_disconnect() is now notified when a _hangup() is pending.
If a hangup is pending, it will not release the driver module and will
let _hangup() do that.

Signed-off-by: Joel Becker <joel.becker@oracle.com>

1 files changed, 32 insertions, 4 deletions

diff --git a/fs/ocfs2/stackglue.h b/fs/ocfs2/stackglue.h
index 083632215dc5..c96c8bb76863 100644
--- a/fs/ocfs2/stackglue.h
+++ b/fs/ocfs2/stackglue.h
@@ -119,14 +119,21 @@ struct ocfs2_stack_operations {
          * Once ->disconnect() has returned, the connection structure will
          * be freed.  Thus, a stack must not return from ->disconnect()
          * until it will no longer reference the conn pointer.
+         *
+         * If hangup_pending is zero, ocfs2_cluster_disconnect() will also
+         * be dropping the reference on the module.
          */
-        int (*disconnect)(struct ocfs2_cluster_connection *conn);
+        int (*disconnect)(struct ocfs2_cluster_connection *conn,
+                          int hangup_pending);
 
         /*
          * ocfs2_cluster_hangup() exists for compatibility with older
          * ocfs2 tools.  Only the classic stack really needs it.  As such
          * ->hangup() is not required of all stacks.  See the comment by
          * ocfs2_cluster_hangup() for more details.
+         *
+         * Note that ocfs2_cluster_hangup() can only be called if
+         * hangup_pending was passed to ocfs2_cluster_disconnect().
          */
         void (*hangup)(const char *group, int grouplen);
 
@@ -184,13 +191,32 @@ struct ocfs2_stack_operations {
         void (*dump_lksb)(union ocfs2_dlm_lksb *lksb);
 };
 
+/*
+ * Each stack plugin must describe itself by registering a
+ * ocfs2_stack_plugin structure.  This is only seen by stackglue and the
+ * stack driver.
+ */
+struct ocfs2_stack_plugin {
+        char *sp_name;
+        struct ocfs2_stack_operations *sp_ops;
+        struct module *sp_owner;
+
+        /* These are managed by the stackglue code. */
+        struct list_head sp_list;
+        unsigned int sp_count;
+        struct ocfs2_locking_protocol *sp_proto;
+};
+
+
+/* Used by the filesystem */
 int ocfs2_cluster_connect(const char *group,
                           int grouplen,
                           void (*recovery_handler)(int node_num,
                                                    void *recovery_data),
                           void *recovery_data,
                           struct ocfs2_cluster_connection **conn);
-int ocfs2_cluster_disconnect(struct ocfs2_cluster_connection *conn);
+int ocfs2_cluster_disconnect(struct ocfs2_cluster_connection *conn,
+                             int hangup_pending);
 void ocfs2_cluster_hangup(const char *group, int grouplen);
 int ocfs2_cluster_this_node(unsigned int *node);
 
@@ -212,6 +238,8 @@ void ocfs2_dlm_dump_lksb(union ocfs2_dlm_lksb *lksb);
 
 void ocfs2_stack_glue_set_locking_protocol(struct ocfs2_locking_protocol *proto);
 
-extern struct ocfs2_locking_protocol *stack_glue_lproto;
-extern struct ocfs2_stack_operations o2cb_stack_ops;
+
+/* Used by stack plugins */
+int ocfs2_stack_glue_register(struct ocfs2_stack_plugin *plugin);
+void ocfs2_stack_glue_unregister(struct ocfs2_stack_plugin *plugin);
 #endif  /* STACKGLUE_H */