This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / drivers / md / dm-path-selector.c

diff --git a/drivers/md/dm-path-selector.c b/drivers/md/dm-path-selector.c
new file mode 100644 (file)
index 0000000..a28c1c2
--- /dev/null
+++ b/drivers/md/dm-path-selector.c
@@ -0,0 +1,156 @@
+/*
+ * Copyright (C) 2003 Sistina Software.
+ * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
+ *
+ * Module Author: Heinz Mauelshagen
+ *
+ * This file is released under the GPL.
+ *
+ * Path selector registration.
+ */
+
+#include "dm.h"
+#include "dm-path-selector.h"
+
+#include <linux/slab.h>
+
+struct ps_internal {
+       struct path_selector_type pst;
+
+       struct list_head list;
+       long use;
+};
+
+#define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
+
+static LIST_HEAD(_path_selectors);
+static DECLARE_RWSEM(_ps_lock);
+
+static struct ps_internal *__find_path_selector_type(const char *name)
+{
+       struct ps_internal *psi;
+
+       list_for_each_entry(psi, &_path_selectors, list) {
+               if (!strcmp(name, psi->pst.name))
+                       return psi;
+       }
+
+       return NULL;
+}
+
+static struct ps_internal *get_path_selector(const char *name)
+{
+       struct ps_internal *psi;
+
+       down_read(&_ps_lock);
+       psi = __find_path_selector_type(name);
+       if (psi) {
+               if ((psi->use == 0) && !try_module_get(psi->pst.module))
+                       psi = NULL;
+               else
+                       psi->use++;
+       }
+       up_read(&_ps_lock);
+
+       return psi;
+}
+
+struct path_selector_type *dm_get_path_selector(const char *name)
+{
+       struct ps_internal *psi;
+
+       if (!name)
+               return NULL;
+
+       psi = get_path_selector(name);
+       if (!psi) {
+               request_module("dm-%s", name);
+               psi = get_path_selector(name);
+       }
+
+       return psi ? &psi->pst : NULL;
+}
+
+void dm_put_path_selector(struct path_selector_type *pst)
+{
+       struct ps_internal *psi;
+
+       if (!pst)
+               return;
+
+       down_read(&_ps_lock);
+       psi = __find_path_selector_type(pst->name);
+       if (!psi)
+               goto out;
+
+       if (--psi->use == 0)
+               module_put(psi->pst.module);
+
+       if (psi->use < 0)
+               BUG();
+
+out:
+       up_read(&_ps_lock);
+}
+
+static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
+{
+       struct ps_internal *psi = kmalloc(sizeof(*psi), GFP_KERNEL);
+
+       if (psi) {
+               memset(psi, 0, sizeof(*psi));
+               psi->pst = *pst;
+       }
+
+       return psi;
+}
+
+int dm_register_path_selector(struct path_selector_type *pst)
+{
+       int r = 0;
+       struct ps_internal *psi = _alloc_path_selector(pst);
+
+       if (!psi)
+               return -ENOMEM;
+
+       down_write(&_ps_lock);
+
+       if (__find_path_selector_type(pst->name)) {
+               kfree(psi);
+               r = -EEXIST;
+       } else
+               list_add(&psi->list, &_path_selectors);
+
+       up_write(&_ps_lock);
+
+       return r;
+}
+
+int dm_unregister_path_selector(struct path_selector_type *pst)
+{
+       struct ps_internal *psi;
+
+       down_write(&_ps_lock);
+
+       psi = __find_path_selector_type(pst->name);
+       if (!psi) {
+               up_write(&_ps_lock);
+               return -EINVAL;
+       }
+
+       if (psi->use) {
+               up_write(&_ps_lock);
+               return -ETXTBSY;
+       }
+
+       list_del(&psi->list);
+
+       up_write(&_ps_lock);
+
+       kfree(psi);
+
+       return 0;
+}
+
+EXPORT_SYMBOL_GPL(dm_register_path_selector);
+EXPORT_SYMBOL_GPL(dm_unregister_path_selector);