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, 214 insertions, 24 deletions

diff --git a/fs/ocfs2/stackglue.c b/fs/ocfs2/stackglue.c
index e197367b6bd6..1978c9cff0e9 100644
--- a/fs/ocfs2/stackglue.c
+++ b/fs/ocfs2/stackglue.c
@@ -18,17 +18,176 @@
  * General Public License for more details.
  */
 
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/kmod.h>
 
-/* Needed for AOP_TRUNCATED_PAGE in mlog_errno() */
-#include <linux/fs.h>
+#include "stackglue.h"
 
-#include "cluster/masklog.h"
+static struct ocfs2_locking_protocol *lproto;
+static DEFINE_SPINLOCK(ocfs2_stack_lock);
+static LIST_HEAD(ocfs2_stack_list);
 
-#include "stackglue.h"
+/*
+ * The stack currently in use.  If not null, active_stack->sp_count > 0,
+ * the module is pinned, and the locking protocol cannot be changed.
+ */
+static struct ocfs2_stack_plugin *active_stack;
+
+static struct ocfs2_stack_plugin *ocfs2_stack_lookup(const char *name)
+{
+        struct ocfs2_stack_plugin *p;
+
+        assert_spin_locked(&ocfs2_stack_lock);
+
+        list_for_each_entry(p, &ocfs2_stack_list, sp_list) {
+                if (!strcmp(p->sp_name, name))
+                        return p;
+        }
+
+        return NULL;
+}
+
+static int ocfs2_stack_driver_request(const char *name)
+{
+        int rc;
+        struct ocfs2_stack_plugin *p;
+
+        spin_lock(&ocfs2_stack_lock);
+
+        if (active_stack) {
+                /*
+                 * If the active stack isn't the one we want, it cannot
+                 * be selected right now.
+                 */
+                if (!strcmp(active_stack->sp_name, name))
+                        rc = 0;
+                else
+                        rc = -EBUSY;
+                goto out;
+        }
+
+        p = ocfs2_stack_lookup(name);
+        if (!p || !try_module_get(p->sp_owner)) {
+                rc = -ENOENT;
+                goto out;
+        }
+
+        /* Ok, the stack is pinned */
+        p->sp_count++;
+        active_stack = p;
+
+        rc = 0;
+
+out:
+        spin_unlock(&ocfs2_stack_lock);
+        return rc;
+}
+
+/*
+ * This function looks up the appropriate stack and makes it active.  If
+ * there is no stack, it tries to load it.  It will fail if the stack still
+ * cannot be found.  It will also fail if a different stack is in use.
+ */
+static int ocfs2_stack_driver_get(const char *name)
+{
+        int rc;
+
+        rc = ocfs2_stack_driver_request(name);
+        if (rc == -ENOENT) {
+                request_module("ocfs2_stack_%s", name);
+                rc = ocfs2_stack_driver_request(name);
+        }
+
+        if (rc == -ENOENT) {
+                printk(KERN_ERR
+                       "ocfs2: Cluster stack driver \"%s\" cannot be found\n",
+                       name);
+        } else if (rc == -EBUSY) {
+                printk(KERN_ERR
+                       "ocfs2: A different cluster stack driver is in use\n");
+        }
+
+        return rc;
+}
 
-struct ocfs2_locking_protocol *stack_glue_lproto;
+static void ocfs2_stack_driver_put(void)
+{
+        spin_lock(&ocfs2_stack_lock);
+        BUG_ON(active_stack == NULL);
+        BUG_ON(active_stack->sp_count == 0);
+
+        active_stack->sp_count--;
+        if (!active_stack->sp_count) {
+                module_put(active_stack->sp_owner);
+                active_stack = NULL;
+        }
+        spin_unlock(&ocfs2_stack_lock);
+}
+
+int ocfs2_stack_glue_register(struct ocfs2_stack_plugin *plugin)
+{
+        int rc;
+
+        spin_lock(&ocfs2_stack_lock);
+        if (!ocfs2_stack_lookup(plugin->sp_name)) {
+                plugin->sp_count = 0;
+                plugin->sp_proto = lproto;
+                list_add(&plugin->sp_list, &ocfs2_stack_list);
+                printk(KERN_INFO "ocfs2: Registered cluster interface %s\n",
+                       plugin->sp_name);
+                rc = 0;
+        } else {
+                printk(KERN_ERR "ocfs2: Stack \"%s\" already registered\n",
+                       plugin->sp_name);
+                rc = -EEXIST;
+        }
+        spin_unlock(&ocfs2_stack_lock);
+
+        return rc;
+}
+EXPORT_SYMBOL_GPL(ocfs2_stack_glue_register);
+
+void ocfs2_stack_glue_unregister(struct ocfs2_stack_plugin *plugin)
+{
+        struct ocfs2_stack_plugin *p;
+
+        spin_lock(&ocfs2_stack_lock);
+        p = ocfs2_stack_lookup(plugin->sp_name);
+        if (p) {
+                BUG_ON(p != plugin);
+                BUG_ON(plugin == active_stack);
+                BUG_ON(plugin->sp_count != 0);
+                list_del_init(&plugin->sp_list);
+                printk(KERN_INFO "ocfs2: Unregistered cluster interface %s\n",
+                       plugin->sp_name);
+        } else {
+                printk(KERN_ERR "Stack \"%s\" is not registered\n",
+                       plugin->sp_name);
+        }
+        spin_unlock(&ocfs2_stack_lock);
+}
+EXPORT_SYMBOL_GPL(ocfs2_stack_glue_unregister);
+
+void ocfs2_stack_glue_set_locking_protocol(struct ocfs2_locking_protocol *proto)
+{
+        struct ocfs2_stack_plugin *p;
+
+        BUG_ON(proto == NULL);
+
+        spin_lock(&ocfs2_stack_lock);
+        BUG_ON(active_stack != NULL);
+
+        lproto = proto;
+        list_for_each_entry(p, &ocfs2_stack_list, sp_list) {
+                p->sp_proto = lproto;
+        }
+
+        spin_unlock(&ocfs2_stack_lock);
+}
+EXPORT_SYMBOL_GPL(ocfs2_stack_glue_set_locking_protocol);
 
 
 int ocfs2_dlm_lock(struct ocfs2_cluster_connection *conn,
@@ -39,26 +198,29 @@ int ocfs2_dlm_lock(struct ocfs2_cluster_connection *conn,
                    unsigned int namelen,
                    void *astarg)
 {
-        BUG_ON(stack_glue_lproto == NULL);
+        BUG_ON(lproto == NULL);
 
-        return o2cb_stack_ops.dlm_lock(conn, mode, lksb, flags,
-                                       name, namelen, astarg);
+        return active_stack->sp_ops->dlm_lock(conn, mode, lksb, flags,
+                                              name, namelen, astarg);
 }
+EXPORT_SYMBOL_GPL(ocfs2_dlm_lock);
 
 int ocfs2_dlm_unlock(struct ocfs2_cluster_connection *conn,
                      union ocfs2_dlm_lksb *lksb,
                      u32 flags,
                      void *astarg)
 {
-        BUG_ON(stack_glue_lproto == NULL);
+        BUG_ON(lproto == NULL);
 
-        return o2cb_stack_ops.dlm_unlock(conn, lksb, flags, astarg);
+        return active_stack->sp_ops->dlm_unlock(conn, lksb, flags, astarg);
 }
+EXPORT_SYMBOL_GPL(ocfs2_dlm_unlock);
 
 int ocfs2_dlm_lock_status(union ocfs2_dlm_lksb *lksb)
 {
-        return o2cb_stack_ops.lock_status(lksb);
+        return active_stack->sp_ops->lock_status(lksb);
 }
+EXPORT_SYMBOL_GPL(ocfs2_dlm_lock_status);
 
 /*
  * Why don't we cast to ocfs2_meta_lvb?  The "clean" answer is that we
@@ -67,13 +229,15 @@ int ocfs2_dlm_lock_status(union ocfs2_dlm_lksb *lksb)
  */
 void *ocfs2_dlm_lvb(union ocfs2_dlm_lksb *lksb)
 {
-        return o2cb_stack_ops.lock_lvb(lksb);
+        return active_stack->sp_ops->lock_lvb(lksb);
 }
+EXPORT_SYMBOL_GPL(ocfs2_dlm_lvb);
 
 void ocfs2_dlm_dump_lksb(union ocfs2_dlm_lksb *lksb)
 {
-        o2cb_stack_ops.dump_lksb(lksb);
+        active_stack->sp_ops->dump_lksb(lksb);
 }
+EXPORT_SYMBOL_GPL(ocfs2_dlm_dump_lksb);
 
 int ocfs2_cluster_connect(const char *group,
                           int grouplen,
@@ -107,11 +271,16 @@ int ocfs2_cluster_connect(const char *group,
         new_conn->cc_recovery_data = recovery_data;
 
         /* Start the new connection at our maximum compatibility level */
-        new_conn->cc_version = stack_glue_lproto->lp_max_version;
+        new_conn->cc_version = lproto->lp_max_version;
+
+        /* This will pin the stack driver if successful */
+        rc = ocfs2_stack_driver_get("o2cb");
+        if (rc)
+                goto out_free;
 
-        rc = o2cb_stack_ops.connect(new_conn);
+        rc = active_stack->sp_ops->connect(new_conn);
         if (rc) {
-                mlog_errno(rc);
+                ocfs2_stack_driver_put();
                 goto out_free;
         }
 
@@ -124,39 +293,60 @@ out_free:
 out:
         return rc;
 }
+EXPORT_SYMBOL_GPL(ocfs2_cluster_connect);
 
-int ocfs2_cluster_disconnect(struct ocfs2_cluster_connection *conn)
+/* If hangup_pending is 0, the stack driver will be dropped */
+int ocfs2_cluster_disconnect(struct ocfs2_cluster_connection *conn,
+                             int hangup_pending)
 {
         int ret;
 
         BUG_ON(conn == NULL);
 
-        ret = o2cb_stack_ops.disconnect(conn);
+        ret = active_stack->sp_ops->disconnect(conn, hangup_pending);
 
         /* XXX Should we free it anyway? */
-        if (!ret)
+        if (!ret) {
                 kfree(conn);
+                if (!hangup_pending)
+                        ocfs2_stack_driver_put();
+        }
 
         return ret;
 }
+EXPORT_SYMBOL_GPL(ocfs2_cluster_disconnect);
 
 void ocfs2_cluster_hangup(const char *group, int grouplen)
 {
         BUG_ON(group == NULL);
         BUG_ON(group[grouplen] != '\0');
 
-        o2cb_stack_ops.hangup(group, grouplen);
+        active_stack->sp_ops->hangup(group, grouplen);
+
+        /* cluster_disconnect() was called with hangup_pending==1 */
+        ocfs2_stack_driver_put();
 }
+EXPORT_SYMBOL_GPL(ocfs2_cluster_hangup);
 
 int ocfs2_cluster_this_node(unsigned int *node)
 {
-        return o2cb_stack_ops.this_node(node);
+        return active_stack->sp_ops->this_node(node);
 }
+EXPORT_SYMBOL_GPL(ocfs2_cluster_this_node);
 
-void ocfs2_stack_glue_set_locking_protocol(struct ocfs2_locking_protocol *proto)
+
+static int __init ocfs2_stack_glue_init(void)
 {
-        BUG_ON(proto != NULL);
+        return 0;
+}
 
-        stack_glue_lproto = proto;
+static void __exit ocfs2_stack_glue_exit(void)
+{
+        lproto = NULL;
 }
 
+MODULE_AUTHOR("Oracle");
+MODULE_DESCRIPTION("ocfs2 cluter stack glue layer");
+MODULE_LICENSE("GPL");
+module_init(ocfs2_stack_glue_init);
+module_exit(ocfs2_stack_glue_exit);