LXR linux/fs/sysfs/dir.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * fs/sysfs/dir.c - sysfs core and dir operation implementation
   4 *
   5 * Copyright (c) 2001-3 Patrick Mochel
   6 * Copyright (c) 2007 SUSE Linux Products GmbH
   7 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   8 *
   9 * Please see Documentation/filesystems/sysfs.rst for more information.
  10 */
  11
  12#define pr_fmt(fmt)     "sysfs: " fmt
  13
  14#include <linux/fs.h>
  15#include <linux/kobject.h>
  16#include <linux/slab.h>
  17#include "sysfs.h"
  18
  19DEFINE_SPINLOCK(sysfs_symlink_target_lock);
  20
  21void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
  22{
  23        char *buf;
  24
  25        buf = kzalloc(PATH_MAX, GFP_KERNEL);
  26        if (buf)
  27                kernfs_path(parent, buf, PATH_MAX);
  28
  29        pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
  30        dump_stack();
  31
  32        kfree(buf);
  33}
  34
  35/**
  36 * sysfs_create_dir_ns - create a directory for an object with a namespace tag
  37 * @kobj: object we're creating directory for
  38 * @ns: the namespace tag to use
  39 */
  40int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
  41{
  42        struct kernfs_node *parent, *kn;
  43        kuid_t uid;
  44        kgid_t gid;
  45
  46        if (WARN_ON(!kobj))
  47                return -EINVAL;
  48
  49        if (kobj->parent)
  50                parent = kobj->parent->sd;
  51        else
  52                parent = sysfs_root_kn;
  53
  54        if (!parent)
  55                return -ENOENT;
  56
  57        kobject_get_ownership(kobj, &uid, &gid);
  58
  59        kn = kernfs_create_dir_ns(parent, kobject_name(kobj), 0755, uid, gid,
  60                                  kobj, ns);
  61        if (IS_ERR(kn)) {
  62                if (PTR_ERR(kn) == -EEXIST)
  63                        sysfs_warn_dup(parent, kobject_name(kobj));
  64                return PTR_ERR(kn);
  65        }
  66
  67        kobj->sd = kn;
  68        return 0;
  69}
  70
  71/**
  72 *      sysfs_remove_dir - remove an object's directory.
  73 *      @kobj:  object.
  74 *
  75 *      The only thing special about this is that we remove any files in
  76 *      the directory before we remove the directory, and we've inlined
  77 *      what used to be sysfs_rmdir() below, instead of calling separately.
  78 */
  79void sysfs_remove_dir(struct kobject *kobj)
  80{
  81        struct kernfs_node *kn = kobj->sd;
  82
  83        /*
  84         * In general, kboject owner is responsible for ensuring removal
  85         * doesn't race with other operations and sysfs doesn't provide any
  86         * protection; however, when @kobj is used as a symlink target, the
  87         * symlinking entity usually doesn't own @kobj and thus has no
  88         * control over removal.  @kobj->sd may be removed anytime
  89         * and symlink code may end up dereferencing an already freed node.
  90         *
  91         * sysfs_symlink_target_lock synchronizes @kobj->sd
  92         * disassociation against symlink operations so that symlink code
  93         * can safely dereference @kobj->sd.
  94         */
  95        spin_lock(&sysfs_symlink_target_lock);
  96        kobj->sd = NULL;
  97        spin_unlock(&sysfs_symlink_target_lock);
  98
  99        if (kn) {
 100                WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 101                kernfs_remove(kn);
 102        }
 103}
 104
 105int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
 106                        const void *new_ns)
 107{
 108        struct kernfs_node *parent;
 109        int ret;
 110
 111        parent = kernfs_get_parent(kobj->sd);
 112        ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
 113        kernfs_put(parent);
 114        return ret;
 115}
 116
 117int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
 118                      const void *new_ns)
 119{
 120        struct kernfs_node *kn = kobj->sd;
 121        struct kernfs_node *new_parent;
 122
 123        new_parent = new_parent_kobj && new_parent_kobj->sd ?
 124                new_parent_kobj->sd : sysfs_root_kn;
 125
 126        return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
 127}
 128
 129/**
 130 * sysfs_create_mount_point - create an always empty directory
 131 * @parent_kobj:  kobject that will contain this always empty directory
 132 * @name: The name of the always empty directory to add
 133 */
 134int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
 135{
 136        struct kernfs_node *kn, *parent = parent_kobj->sd;
 137
 138        kn = kernfs_create_empty_dir(parent, name);
 139        if (IS_ERR(kn)) {
 140                if (PTR_ERR(kn) == -EEXIST)
 141                        sysfs_warn_dup(parent, name);
 142                return PTR_ERR(kn);
 143        }
 144
 145        return 0;
 146}
 147EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
 148
 149/**
 150 *      sysfs_remove_mount_point - remove an always empty directory.
 151 *      @parent_kobj: kobject that will contain this always empty directory
 152 *      @name: The name of the always empty directory to remove
 153 *
 154 */
 155void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
 156{
 157        struct kernfs_node *parent = parent_kobj->sd;
 158
 159        kernfs_remove_by_name_ns(parent, name, NULL);
 160}
 161EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);
 162