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 static void config_item_init(struct config_item *item)
  51 {
  52         kref_init(&item->ci_kref);
  53         INIT_LIST_HEAD(&item->ci_entry);
  54 }
  55
  56 /**
  57  *      config_item_set_name - Set the name of an item
  58  *      @item:  item.
  59  *      @fmt:  The vsnprintf()'s format string.
  60  *
  61  *      If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
  62  *      dynamically allocated string that @item->ci_name points to.
  63  *      Otherwise, use the static @item->ci_namebuf array.
  64  */
  65 int config_item_set_name(struct config_item *item, const char *fmt, ...)
  66 {
  67         int limit = CONFIGFS_ITEM_NAME_LEN;
  68         int need;
  69         va_list args;
  70         char *name;
  71
  72         /*
  73          * First, try the static array
  74          */
  75         va_start(args, fmt);
  76         need = vsnprintf(item->ci_namebuf, limit, fmt, args);
  77         va_end(args);
  78         if (need < limit)
  79                 name = item->ci_namebuf;
  80         else {
  81                 va_start(args, fmt);
  82                 name = kvasprintf(GFP_KERNEL, fmt, args);
  83                 va_end(args);
  84                 if (!name)
  85                         return -EFAULT;
  86         }
  87
  88         /* Free the old name, if necessary. */
  89         if (item->ci_name && item->ci_name != item->ci_namebuf)
  90                 kfree(item->ci_name);
  91
  92         /* Now, set the new name */
  93         item->ci_name = name;
  94         return 0;
  95 }
  96 EXPORT_SYMBOL(config_item_set_name);
  97
  98 void config_item_init_type_name(struct config_item *item,
  99                                 const char *name,
 100                                 const struct config_item_type *type)
 101 {
 102         config_item_set_name(item, "%s", name);
 103         item->ci_type = type;
 104         config_item_init(item);
 105 }
 106 EXPORT_SYMBOL(config_item_init_type_name);
 107
 108 void config_group_init_type_name(struct config_group *group, const char *name,
 109                          const struct config_item_type *type)
 110 {
 111         config_item_set_name(&group->cg_item, "%s", name);
 112         group->cg_item.ci_type = type;
 113         config_group_init(group);
 114 }
 115 EXPORT_SYMBOL(config_group_init_type_name);
 116
 117 struct config_item *config_item_get(struct config_item *item)
 118 {
 119         if (item)
 120                 kref_get(&item->ci_kref);
 121         return item;
 122 }
 123 EXPORT_SYMBOL(config_item_get);
 124
 125 struct config_item *config_item_get_unless_zero(struct config_item *item)
 126 {
 127         if (item && kref_get_unless_zero(&item->ci_kref))
 128                 return item;
 129         return NULL;
 130 }
 131 EXPORT_SYMBOL(config_item_get_unless_zero);
 132
 133 static void config_item_cleanup(struct config_item *item)
 134 {
 135         const struct config_item_type *t = item->ci_type;
 136         struct config_group *s = item->ci_group;
 137         struct config_item *parent = item->ci_parent;
 138
 139         pr_debug("config_item %s: cleaning up\n", config_item_name(item));
 140         if (item->ci_name != item->ci_namebuf)
 141                 kfree(item->ci_name);
 142         item->ci_name = NULL;
 143         if (t && t->ct_item_ops && t->ct_item_ops->release)
 144                 t->ct_item_ops->release(item);
 145         if (s)
 146                 config_group_put(s);
 147         if (parent)
 148                 config_item_put(parent);
 149 }
 150
 151 static void config_item_release(struct kref *kref)
 152 {
 153         config_item_cleanup(container_of(kref, struct config_item, ci_kref));
 154 }
 155
 156 /**
 157  *      config_item_put - decrement refcount for item.
 158  *      @item:  item.
 159  *
 160  *      Decrement the refcount, and if 0, call config_item_cleanup().
 161  */
 162 void config_item_put(struct config_item *item)
 163 {
 164         if (item)
 165                 kref_put(&item->ci_kref, config_item_release);
 166 }
 167 EXPORT_SYMBOL(config_item_put);
 168
 169 /**
 170  *      config_group_init - initialize a group for use
 171  *      @group: config_group
 172  */
 173 void config_group_init(struct config_group *group)
 174 {
 175         config_item_init(&group->cg_item);
 176         INIT_LIST_HEAD(&group->cg_children);
 177         INIT_LIST_HEAD(&group->default_groups);
 178 }
 179 EXPORT_SYMBOL(config_group_init);
 180
 181 /**
 182  *      config_group_find_item - search for item in group.
 183  *      @group: group we're looking in.
 184  *      @name:  item's name.
 185  *
 186  *      Iterate over @group->cg_list, looking for a matching config_item.
 187  *      If matching item is found take a reference and return the item.
 188  *      Caller must have locked group via @group->cg_subsys->su_mtx.
 189  */
 190 struct config_item *config_group_find_item(struct config_group *group,
 191                                            const char *name)
 192 {
 193         struct list_head *entry;
 194         struct config_item *ret = NULL;
 195
 196         list_for_each(entry, &group->cg_children) {
 197                 struct config_item *item = to_item(entry);
 198                 if (config_item_name(item) &&
 199                     !strcmp(config_item_name(item), name)) {
 200                         ret = config_item_get(item);
 201                         break;
 202                 }
 203         }
 204         return ret;
 205 }
 206 EXPORT_SYMBOL(config_group_find_item);