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.txt 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
  19 DEFINE_SPINLOCK(sysfs_symlink_target_lock);
  20
  21 void 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  */
  40 int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
  41 {
  42         struct kernfs_node *parent, *kn;
  43
  44         BUG_ON(!kobj);
  45
  46         if (kobj->parent)
  47                 parent = kobj->parent->sd;
  48         else
  49                 parent = sysfs_root_kn;
  50
  51         if (!parent)
  52                 return -ENOENT;
  53
  54         kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
  55                                   S_IRWXU | S_IRUGO | S_IXUGO, kobj, ns);
  56         if (IS_ERR(kn)) {
  57                 if (PTR_ERR(kn) == -EEXIST)
  58                         sysfs_warn_dup(parent, kobject_name(kobj));
  59                 return PTR_ERR(kn);
  60         }
  61
  62         kobj->sd = kn;
  63         return 0;
  64 }
  65
  66 /**
  67  *      sysfs_remove_dir - remove an object's directory.
  68  *      @kobj:  object.
  69  *
  70  *      The only thing special about this is that we remove any files in
  71  *      the directory before we remove the directory, and we've inlined
  72  *      what used to be sysfs_rmdir() below, instead of calling separately.
  73  */
  74 void sysfs_remove_dir(struct kobject *kobj)
  75 {
  76         struct kernfs_node *kn = kobj->sd;
  77
  78         /*
  79          * In general, kboject owner is responsible for ensuring removal
  80          * doesn't race with other operations and sysfs doesn't provide any
  81          * protection; however, when @kobj is used as a symlink target, the
  82          * symlinking entity usually doesn't own @kobj and thus has no
  83          * control over removal.  @kobj->sd may be removed anytime
  84          * and symlink code may end up dereferencing an already freed node.
  85          *
  86          * sysfs_symlink_target_lock synchronizes @kobj->sd
  87          * disassociation against symlink operations so that symlink code
  88          * can safely dereference @kobj->sd.
  89          */
  90         spin_lock(&sysfs_symlink_target_lock);
  91         kobj->sd = NULL;
  92         spin_unlock(&sysfs_symlink_target_lock);
  93
  94         if (kn) {
  95                 WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
  96                 kernfs_remove(kn);
  97         }
  98 }
  99
 100 int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
 101                         const void *new_ns)
 102 {
 103         struct kernfs_node *parent;
 104         int ret;
 105
 106         parent = kernfs_get_parent(kobj->sd);
 107         ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
 108         kernfs_put(parent);
 109         return ret;
 110 }
 111
 112 int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
 113                       const void *new_ns)
 114 {
 115         struct kernfs_node *kn = kobj->sd;
 116         struct kernfs_node *new_parent;
 117
 118         new_parent = new_parent_kobj && new_parent_kobj->sd ?
 119                 new_parent_kobj->sd : sysfs_root_kn;
 120
 121         return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
 122 }
 123
 124 /**
 125  * sysfs_create_mount_point - create an always empty directory
 126  * @parent_kobj:  kobject that will contain this always empty directory
 127  * @name: The name of the always empty directory to add
 128  */
 129 int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
 130 {
 131         struct kernfs_node *kn, *parent = parent_kobj->sd;
 132
 133         kn = kernfs_create_empty_dir(parent, name);
 134         if (IS_ERR(kn)) {
 135                 if (PTR_ERR(kn) == -EEXIST)
 136                         sysfs_warn_dup(parent, name);
 137                 return PTR_ERR(kn);
 138         }
 139
 140         return 0;
 141 }
 142 EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
 143
 144 /**
 145  *      sysfs_remove_mount_point - remove an always empty directory.
 146  *      @parent_kobj: kobject that will contain this always empty directory
 147  *      @name: The name of the always empty directory to remove
 148  *
 149  */
 150 void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
 151 {
 152         struct kernfs_node *parent = parent_kobj->sd;
 153
 154         kernfs_remove_by_name_ns(parent, name, NULL);
 155 }
 156 EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);