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 error = 0;
  68         int limit = CONFIGFS_ITEM_NAME_LEN;
  69         int need;
  70         va_list args;
  71         char *name;
  72
  73         /*
  74          * First, try the static array
  75          */
  76         va_start(args, fmt);
  77         need = vsnprintf(item->ci_namebuf, limit, fmt, args);
  78         va_end(args);
  79         if (need < limit)
  80                 name = item->ci_namebuf;
  81         else {
  82                 /*
  83                  * Need more space? Allocate it and try again
  84                  */
  85                 limit = need + 1;
  86                 name = kmalloc(limit, GFP_KERNEL);
  87                 if (!name) {
  88                         error = -ENOMEM;
  89                         goto Done;
  90                 }
  91                 va_start(args, fmt);
  92                 need = vsnprintf(name, limit, fmt, args);
  93                 va_end(args);
  94
  95                 /* Still? Give up. */
  96                 if (need >= limit) {
  97                         kfree(name);
  98                         error = -EFAULT;
  99                         goto Done;
 100                 }
 101         }
 102
 103         /* Free the old name, if necessary. */
 104         if (item->ci_name && item->ci_name != item->ci_namebuf)
 105                 kfree(item->ci_name);
 106
 107         /* Now, set the new name */
 108         item->ci_name = name;
 109  Done:
 110         return error;
 111 }
 112 EXPORT_SYMBOL(config_item_set_name);
 113
 114 void config_item_init_type_name(struct config_item *item,
 115                                 const char *name,
 116                                 struct config_item_type *type)
 117 {
 118         config_item_set_name(item, "%s", name);
 119         item->ci_type = type;
 120         config_item_init(item);
 121 }
 122 EXPORT_SYMBOL(config_item_init_type_name);
 123
 124 void config_group_init_type_name(struct config_group *group, const char *name,
 125                          struct config_item_type *type)
 126 {
 127         config_item_set_name(&group->cg_item, "%s", name);
 128         group->cg_item.ci_type = type;
 129         config_group_init(group);
 130 }
 131 EXPORT_SYMBOL(config_group_init_type_name);
 132
 133 struct config_item *config_item_get(struct config_item *item)
 134 {
 135         if (item)
 136                 kref_get(&item->ci_kref);
 137         return item;
 138 }
 139 EXPORT_SYMBOL(config_item_get);
 140
 141 struct config_item *config_item_get_unless_zero(struct config_item *item)
 142 {
 143         if (item && kref_get_unless_zero(&item->ci_kref))
 144                 return item;
 145         return NULL;
 146 }
 147 EXPORT_SYMBOL(config_item_get_unless_zero);
 148
 149 static void config_item_cleanup(struct config_item *item)
 150 {
 151         struct config_item_type *t = item->ci_type;
 152         struct config_group *s = item->ci_group;
 153         struct config_item *parent = item->ci_parent;
 154
 155         pr_debug("config_item %s: cleaning up\n", config_item_name(item));
 156         if (item->ci_name != item->ci_namebuf)
 157                 kfree(item->ci_name);
 158         item->ci_name = NULL;
 159         if (t && t->ct_item_ops && t->ct_item_ops->release)
 160                 t->ct_item_ops->release(item);
 161         if (s)
 162                 config_group_put(s);
 163         if (parent)
 164                 config_item_put(parent);
 165 }
 166
 167 static void config_item_release(struct kref *kref)
 168 {
 169         config_item_cleanup(container_of(kref, struct config_item, ci_kref));
 170 }
 171
 172 /**
 173  *      config_item_put - decrement refcount for item.
 174  *      @item:  item.
 175  *
 176  *      Decrement the refcount, and if 0, call config_item_cleanup().
 177  */
 178 void config_item_put(struct config_item *item)
 179 {
 180         if (item)
 181                 kref_put(&item->ci_kref, config_item_release);
 182 }
 183 EXPORT_SYMBOL(config_item_put);
 184
 185 /**
 186  *      config_group_init - initialize a group for use
 187  *      @group: config_group
 188  */
 189 void config_group_init(struct config_group *group)
 190 {
 191         config_item_init(&group->cg_item);
 192         INIT_LIST_HEAD(&group->cg_children);
 193         INIT_LIST_HEAD(&group->default_groups);
 194 }
 195 EXPORT_SYMBOL(config_group_init);
 196
 197 /**
 198  *      config_group_find_item - search for item in group.
 199  *      @group: group we're looking in.
 200  *      @name:  item's name.
 201  *
 202  *      Iterate over @group->cg_list, looking for a matching config_item.
 203  *      If matching item is found take a reference and return the item.
 204  *      Caller must have locked group via @group->cg_subsys->su_mtx.
 205  */
 206 struct config_item *config_group_find_item(struct config_group *group,
 207                                            const char *name)
 208 {
 209         struct list_head *entry;
 210         struct config_item *ret = NULL;
 211
 212         list_for_each(entry, &group->cg_children) {
 213                 struct config_item *item = to_item(entry);
 214                 if (config_item_name(item) &&
 215                     !strcmp(config_item_name(item), name)) {
 216                         ret = config_item_get(item);
 217                         break;
 218                 }
 219         }
 220         return ret;
 221 }
 222 EXPORT_SYMBOL(config_group_find_item);