fs/configfs/item.c

   1 /* -*- mode: c; c-basic-offset: 8; -*-
   2  * vim: noexpandtab sw=8 ts=8 sts=0:
   3  *
   4  * item.c - library routines for handling generic config items
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public
  17  * License along with this program; if not, write to the
  18  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19  * Boston, MA 021110-1307, USA.
  20  *
  21  * Based on kobject:
  22  *      kobject is Copyright (c) 2002-2003 Patrick Mochel
  23  *
  24  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
  25  *
  26  * Please see the file Documentation/filesystems/configfs/configfs.txt for
  27  * critical information about using the config_item interface.
  28  */
  29
  30 #include <linux/string.h>
  31 #include <linux/module.h>
  32 #include <linux/stat.h>
  33 #include <linux/slab.h>
  34
  35 #include <linux/configfs.h>
  36
  37
  38 static inline struct config_item *to_item(struct list_head *entry)
  39 {
  40         return container_of(entry, struct config_item, ci_entry);
  41 }
  42
  43 /* Evil kernel */
  44 static void config_item_release(struct kref *kref);
  45
  46 /**
  47  *      config_item_init - initialize item.
  48  *      @item:  item in question.
  49  */
  50 void config_item_init(struct config_item *item)
  51 {
  52         kref_init(&item->ci_kref);
  53         INIT_LIST_HEAD(&item->ci_entry);
  54 }
  55 EXPORT_SYMBOL(config_item_init);
  56
  57 /**
  58  *      config_item_set_name - Set the name of an item
  59  *      @item:  item.
  60  *      @fmt:  The vsnprintf()'s format string.
  61  *
  62  *      If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
  63  *      dynamically allocated string that @item->ci_name points to.
  64  *      Otherwise, use the static @item->ci_namebuf array.
  65  */
  66 int config_item_set_name(struct config_item *item, const char *fmt, ...)
  67 {
  68         int error = 0;
  69         int limit = CONFIGFS_ITEM_NAME_LEN;
  70         int need;
  71         va_list args;
  72         char *name;
  73
  74         /*
  75          * First, try the static array
  76          */
  77         va_start(args, fmt);
  78         need = vsnprintf(item->ci_namebuf, limit, fmt, args);
  79         va_end(args);
  80         if (need < limit)
  81                 name = item->ci_namebuf;
  82         else {
  83                 /*
  84                  * Need more space? Allocate it and try again
  85                  */
  86                 limit = need + 1;
  87                 name = kmalloc(limit, GFP_KERNEL);
  88                 if (!name) {
  89                         error = -ENOMEM;
  90                         goto Done;
  91                 }
  92                 va_start(args, fmt);
  93                 need = vsnprintf(name, limit, fmt, args);
  94                 va_end(args);
  95
  96                 /* Still? Give up. */
  97                 if (need >= limit) {
  98                         kfree(name);
  99                         error = -EFAULT;
 100                         goto Done;
 101                 }
 102         }
 103
 104         /* Free the old name, if necessary. */
 105         if (item->ci_name && item->ci_name != item->ci_namebuf)
 106                 kfree(item->ci_name);
 107
 108         /* Now, set the new name */
 109         item->ci_name = name;
 110  Done:
 111         return error;
 112 }
 113 EXPORT_SYMBOL(config_item_set_name);
 114
 115 void config_item_init_type_name(struct config_item *item,
 116                                 const char *name,
 117                                 struct config_item_type *type)
 118 {
 119         config_item_set_name(item, name);
 120         item->ci_type = type;
 121         config_item_init(item);
 122 }
 123 EXPORT_SYMBOL(config_item_init_type_name);
 124
 125 void config_group_init_type_name(struct config_group *group, const char *name,
 126                          struct config_item_type *type)
 127 {
 128         config_item_set_name(&group->cg_item, name);
 129         group->cg_item.ci_type = type;
 130         config_group_init(group);
 131 }
 132 EXPORT_SYMBOL(config_group_init_type_name);
 133
 134 struct config_item *config_item_get(struct config_item *item)
 135 {
 136         if (item)
 137                 kref_get(&item->ci_kref);
 138         return item;
 139 }
 140 EXPORT_SYMBOL(config_item_get);
 141
 142 static void config_item_cleanup(struct config_item *item)
 143 {
 144         struct config_item_type *t = item->ci_type;
 145         struct config_group *s = item->ci_group;
 146         struct config_item *parent = item->ci_parent;
 147
 148         pr_debug("config_item %s: cleaning up\n", config_item_name(item));
 149         if (item->ci_name != item->ci_namebuf)
 150                 kfree(item->ci_name);
 151         item->ci_name = NULL;
 152         if (t && t->ct_item_ops && t->ct_item_ops->release)
 153                 t->ct_item_ops->release(item);
 154         if (s)
 155                 config_group_put(s);
 156         if (parent)
 157                 config_item_put(parent);
 158 }
 159
 160 static void config_item_release(struct kref *kref)
 161 {
 162         config_item_cleanup(container_of(kref, struct config_item, ci_kref));
 163 }
 164
 165 /**
 166  *      config_item_put - decrement refcount for item.
 167  *      @item:  item.
 168  *
 169  *      Decrement the refcount, and if 0, call config_item_cleanup().
 170  */
 171 void config_item_put(struct config_item *item)
 172 {
 173         if (item)
 174                 kref_put(&item->ci_kref, config_item_release);
 175 }
 176 EXPORT_SYMBOL(config_item_put);
 177
 178 /**
 179  *      config_group_init - initialize a group for use
 180  *      @group: config_group
 181  */
 182 void config_group_init(struct config_group *group)
 183 {
 184         config_item_init(&group->cg_item);
 185         INIT_LIST_HEAD(&group->cg_children);
 186 }
 187 EXPORT_SYMBOL(config_group_init);
 188
 189 /**
 190  *      config_group_find_item - search for item in group.
 191  *      @group: group we're looking in.
 192  *      @name:  item's name.
 193  *
 194  *      Iterate over @group->cg_list, looking for a matching config_item.
 195  *      If matching item is found take a reference and return the item.
 196  *      Caller must have locked group via @group->cg_subsys->su_mtx.
 197  */
 198 struct config_item *config_group_find_item(struct config_group *group,
 199                                            const char *name)
 200 {
 201         struct list_head *entry;
 202         struct config_item *ret = NULL;
 203
 204         list_for_each(entry, &group->cg_children) {
 205                 struct config_item *item = to_item(entry);
 206                 if (config_item_name(item) &&
 207                     !strcmp(config_item_name(item), name)) {
 208                         ret = config_item_get(item);
 209                         break;
 210                 }
 211         }
 212         return ret;
 213 }
 214 EXPORT_SYMBOL(config_group_find_item);