[PATCH] configfs: User-driven configuration filesystem

Configfs, a file system for userspace-driven kernel object configuration.
The OCFS2 stack makes extensive use of this for propagation of cluster
configuration information into kernel.

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

1 files changed, 227 insertions, 0 deletions

diff --git a/fs/configfs/item.c b/fs/configfs/item.c
new file mode 100644
index 000000000000..e07485ac50ad
--- /dev/null
+++ b/fs/configfs/item.c
@@ -0,0 +1,227 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * item.c - library routines for handling generic config items
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ * Based on kobject:
+ *      kobject is Copyright (c) 2002-2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ *
+ * Please see the file Documentation/filesystems/configfs.txt for
+ * critical information about using the config_item interface.
+ */
+
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+
+#include <linux/configfs.h>
+
+
+static inline struct config_item * to_item(struct list_head * entry)
+{
+        return container_of(entry,struct config_item,ci_entry);
+}
+
+/* Evil kernel */
+static void config_item_release(struct kref *kref);
+
+/**
+ *      config_item_init - initialize item.
+ *      @item:  item in question.
+ */
+void config_item_init(struct config_item * item)
+{
+        kref_init(&item->ci_kref);
+        INIT_LIST_HEAD(&item->ci_entry);
+}
+
+/**
+ *      config_item_set_name - Set the name of an item
+ *      @item:  item.
+ *      @name:  name.
+ *
+ *      If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
+ *      dynamically allocated string that @item->ci_name points to.
+ *      Otherwise, use the static @item->ci_namebuf array.
+ */
+
+int config_item_set_name(struct config_item * item, const char * fmt, ...)
+{
+        int error = 0;
+        int limit = CONFIGFS_ITEM_NAME_LEN;
+        int need;
+        va_list args;
+        char * name;
+
+        /*
+         * First, try the static array
+         */
+        va_start(args,fmt);
+        need = vsnprintf(item->ci_namebuf,limit,fmt,args);
+        va_end(args);
+        if (need < limit)
+                name = item->ci_namebuf;
+        else {
+                /*
+                 * Need more space? Allocate it and try again
+                 */
+                limit = need + 1;
+                name = kmalloc(limit,GFP_KERNEL);
+                if (!name) {
+                        error = -ENOMEM;
+                        goto Done;
+                }
+                va_start(args,fmt);
+                need = vsnprintf(name,limit,fmt,args);
+                va_end(args);
+
+                /* Still? Give up. */
+                if (need >= limit) {
+                        kfree(name);
+                        error = -EFAULT;
+                        goto Done;
+                }
+        }
+
+        /* Free the old name, if necessary. */
+        if (item->ci_name && item->ci_name != item->ci_namebuf)
+                kfree(item->ci_name);
+
+        /* Now, set the new name */
+        item->ci_name = name;
+ Done:
+        return error;
+}
+
+EXPORT_SYMBOL(config_item_set_name);
+
+void config_item_init_type_name(struct config_item *item,
+                                const char *name,
+                                struct config_item_type *type)
+{
+        config_item_set_name(item, name);
+        item->ci_type = type;
+        config_item_init(item);
+}
+EXPORT_SYMBOL(config_item_init_type_name);
+
+void config_group_init_type_name(struct config_group *group, const char *name,
+                         struct config_item_type *type)
+{
+        config_item_set_name(&group->cg_item, name);
+        group->cg_item.ci_type = type;
+        config_group_init(group);
+}
+EXPORT_SYMBOL(config_group_init_type_name);
+
+struct config_item * config_item_get(struct config_item * item)
+{
+        if (item)
+                kref_get(&item->ci_kref);
+        return item;
+}
+
+/**
+ *      config_item_cleanup - free config_item resources.
+ *      @item:  item.
+ */
+
+void config_item_cleanup(struct config_item * item)
+{
+        struct config_item_type * t = item->ci_type;
+        struct config_group * s = item->ci_group;
+        struct config_item * parent = item->ci_parent;
+
+        pr_debug("config_item %s: cleaning up\n",config_item_name(item));
+        if (item->ci_name != item->ci_namebuf)
+                kfree(item->ci_name);
+        item->ci_name = NULL;
+        if (t && t->ct_item_ops && t->ct_item_ops->release)
+                t->ct_item_ops->release(item);
+        if (s)
+                config_group_put(s);
+        if (parent)
+                config_item_put(parent);
+}
+
+static void config_item_release(struct kref *kref)
+{
+        config_item_cleanup(container_of(kref, struct config_item, ci_kref));
+}
+
+/**
+ *      config_item_put - decrement refcount for item.
+ *      @item:  item.
+ *
+ *      Decrement the refcount, and if 0, call config_item_cleanup().
+ */
+void config_item_put(struct config_item * item)
+{
+        if (item)
+                kref_put(&item->ci_kref, config_item_release);
+}
+
+
+/**
+ *      config_group_init - initialize a group for use
+ *      @k:     group
+ */
+
+void config_group_init(struct config_group *group)
+{
+        config_item_init(&group->cg_item);
+        INIT_LIST_HEAD(&group->cg_children);
+}
+
+
+/**
+ *      config_group_find_obj - search for item in group.
+ *      @group: group we're looking in.
+ *      @name:  item's name.
+ *
+ *      Lock group via @group->cg_subsys, and iterate over @group->cg_list,
+ *      looking for a matching config_item. If matching item is found
+ *      take a reference and return the item.
+ */
+
+struct config_item * config_group_find_obj(struct config_group * group, const char * name)
+{
+        struct list_head * entry;
+        struct config_item * ret = NULL;
+
+        /* XXX LOCKING! */
+        list_for_each(entry,&group->cg_children) {
+                struct config_item * item = to_item(entry);
+                if (config_item_name(item) &&
+                    !strcmp(config_item_name(item), name)) {
+                        ret = config_item_get(item);
+                        break;
+                }
+        }
+        return ret;
+}
+
+
+EXPORT_SYMBOL(config_item_init);
+EXPORT_SYMBOL(config_group_init);
+EXPORT_SYMBOL(config_item_get);
+EXPORT_SYMBOL(config_item_put);
+