linux/fs/configfs/item.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * item.c - library routines for handling generic config items
   4 *
   5 * Based on kobject:
   6 *      kobject is Copyright (c) 2002-2003 Patrick Mochel
   7 *
   8 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   9 *
  10 * Please see the file Documentation/filesystems/configfs.rst for
  11 * critical information about using the config_item interface.
  12 */
  13
  14#include <linux/string.h>
  15#include <linux/module.h>
  16#include <linux/stat.h>
  17#include <linux/slab.h>
  18
  19#include <linux/configfs.h>
  20
  21
  22static inline struct config_item *to_item(struct list_head *entry)
  23{
  24        return container_of(entry, struct config_item, ci_entry);
  25}
  26
  27/* Evil kernel */
  28static void config_item_release(struct kref *kref);
  29
  30/**
  31 *      config_item_init - initialize item.
  32 *      @item:  item in question.
  33 */
  34static void config_item_init(struct config_item *item)
  35{
  36        kref_init(&item->ci_kref);
  37        INIT_LIST_HEAD(&item->ci_entry);
  38}
  39
  40/**
  41 *      config_item_set_name - Set the name of an item
  42 *      @item:  item.
  43 *      @fmt:  The vsnprintf()'s format string.
  44 *
  45 *      If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
  46 *      dynamically allocated string that @item->ci_name points to.
  47 *      Otherwise, use the static @item->ci_namebuf array.
  48 */
  49int config_item_set_name(struct config_item *item, const char *fmt, ...)
  50{
  51        int limit = CONFIGFS_ITEM_NAME_LEN;
  52        int need;
  53        va_list args;
  54        char *name;
  55
  56        /*
  57         * First, try the static array
  58         */
  59        va_start(args, fmt);
  60        need = vsnprintf(item->ci_namebuf, limit, fmt, args);
  61        va_end(args);
  62        if (need < limit)
  63                name = item->ci_namebuf;
  64        else {
  65                va_start(args, fmt);
  66                name = kvasprintf(GFP_KERNEL, fmt, args);
  67                va_end(args);
  68                if (!name)
  69                        return -EFAULT;
  70        }
  71
  72        /* Free the old name, if necessary. */
  73        if (item->ci_name && item->ci_name != item->ci_namebuf)
  74                kfree(item->ci_name);
  75
  76        /* Now, set the new name */
  77        item->ci_name = name;
  78        return 0;
  79}
  80EXPORT_SYMBOL(config_item_set_name);
  81
  82void config_item_init_type_name(struct config_item *item,
  83                                const char *name,
  84                                const struct config_item_type *type)
  85{
  86        config_item_set_name(item, "%s", name);
  87        item->ci_type = type;
  88        config_item_init(item);
  89}
  90EXPORT_SYMBOL(config_item_init_type_name);
  91
  92void config_group_init_type_name(struct config_group *group, const char *name,
  93                         const struct config_item_type *type)
  94{
  95        config_item_set_name(&group->cg_item, "%s", name);
  96        group->cg_item.ci_type = type;
  97        config_group_init(group);
  98}
  99EXPORT_SYMBOL(config_group_init_type_name);
 100
 101struct config_item *config_item_get(struct config_item *item)
 102{
 103        if (item)
 104                kref_get(&item->ci_kref);
 105        return item;
 106}
 107EXPORT_SYMBOL(config_item_get);
 108
 109struct config_item *config_item_get_unless_zero(struct config_item *item)
 110{
 111        if (item && kref_get_unless_zero(&item->ci_kref))
 112                return item;
 113        return NULL;
 114}
 115EXPORT_SYMBOL(config_item_get_unless_zero);
 116
 117static void config_item_cleanup(struct config_item *item)
 118{
 119        const struct config_item_type *t = item->ci_type;
 120        struct config_group *s = item->ci_group;
 121        struct config_item *parent = item->ci_parent;
 122
 123        pr_debug("config_item %s: cleaning up\n", config_item_name(item));
 124        if (item->ci_name != item->ci_namebuf)
 125                kfree(item->ci_name);
 126        item->ci_name = NULL;
 127        if (t && t->ct_item_ops && t->ct_item_ops->release)
 128                t->ct_item_ops->release(item);
 129        if (s)
 130                config_group_put(s);
 131        if (parent)
 132                config_item_put(parent);
 133}
 134
 135static void config_item_release(struct kref *kref)
 136{
 137        config_item_cleanup(container_of(kref, struct config_item, ci_kref));
 138}
 139
 140/**
 141 *      config_item_put - decrement refcount for item.
 142 *      @item:  item.
 143 *
 144 *      Decrement the refcount, and if 0, call config_item_cleanup().
 145 */
 146void config_item_put(struct config_item *item)
 147{
 148        if (item)
 149                kref_put(&item->ci_kref, config_item_release);
 150}
 151EXPORT_SYMBOL(config_item_put);
 152
 153/**
 154 *      config_group_init - initialize a group for use
 155 *      @group: config_group
 156 */
 157void config_group_init(struct config_group *group)
 158{
 159        config_item_init(&group->cg_item);
 160        INIT_LIST_HEAD(&group->cg_children);
 161        INIT_LIST_HEAD(&group->default_groups);
 162}
 163EXPORT_SYMBOL(config_group_init);
 164
 165/**
 166 *      config_group_find_item - search for item in group.
 167 *      @group: group we're looking in.
 168 *      @name:  item's name.
 169 *
 170 *      Iterate over @group->cg_list, looking for a matching config_item.
 171 *      If matching item is found take a reference and return the item.
 172 *      Caller must have locked group via @group->cg_subsys->su_mtx.
 173 */
 174struct config_item *config_group_find_item(struct config_group *group,
 175                                           const char *name)
 176{
 177        struct list_head *entry;
 178        struct config_item *ret = NULL;
 179
 180        list_for_each(entry, &group->cg_children) {
 181                struct config_item *item = to_item(entry);
 182                if (config_item_name(item) &&
 183                    !strcmp(config_item_name(item), name)) {
 184                        ret = config_item_get(item);
 185                        break;
 186                }
 187        }
 188        return ret;
 189}
 190EXPORT_SYMBOL(config_group_find_item);
 191
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