symlink.c
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/*
* fs/sysfs/symlink.c - sysfs symlink implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
*
* This file is released under the GPLv2.
*
* Please see Documentation/filesystems/sysfs.txt for more information.
*/
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/mutex.h>
#include <linux/security.h>
#include "sysfs.h"
static int sysfs_do_create_link_sd(struct kernfs_node *parent,
struct kobject *target_kobj,
const char *name, int warn)
{
struct kernfs_node *kn, *target = NULL;
BUG_ON(!name || !parent);
/*
* We don't own @target_kobj and it may be removed at any time.
* Synchronize using sysfs_symlink_target_lock. See
* sysfs_remove_dir() for details.
*/
spin_lock(&sysfs_symlink_target_lock);
if (target_kobj->sd) {
target = target_kobj->sd;
kernfs_get(target);
}
spin_unlock(&sysfs_symlink_target_lock);
if (!target)
return -ENOENT;
kn = kernfs_create_link(parent, name, target);
kernfs_put(target);
if (!IS_ERR(kn))
return 0;
if (warn && PTR_ERR(kn) == -EEXIST)
sysfs_warn_dup(parent, name);
return PTR_ERR(kn);
}
/**
* sysfs_create_link_sd - create symlink to a given object.
* @kn: directory we're creating the link in.
* @target: object we're pointing to.
* @name: name of the symlink.
*/
int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
const char *name)
{
return sysfs_do_create_link_sd(kn, target, name, 1);
}
static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
const char *name, int warn)
{
struct kernfs_node *parent = NULL;
if (!kobj)
parent = sysfs_root_kn;
else
parent = kobj->sd;
if (!parent)
return -EFAULT;
return sysfs_do_create_link_sd(parent, target, name, warn);
}
/**
* sysfs_create_link - create symlink between two objects.
* @kobj: object whose directory we're creating the link in.
* @target: object we're pointing to.
* @name: name of the symlink.
*/
int sysfs_create_link(struct kobject *kobj, struct kobject *target,
const char *name)
{
return sysfs_do_create_link(kobj, target, name, 1);
}
EXPORT_SYMBOL_GPL(sysfs_create_link);
/**
* sysfs_create_link_nowarn - create symlink between two objects.
* @kobj: object whose directory we're creating the link in.
* @target: object we're pointing to.
* @name: name of the symlink.
*
* This function does the same as sysfs_create_link(), but it
* doesn't warn if the link already exists.
*/
int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
const char *name)
{
return sysfs_do_create_link(kobj, target, name, 0);
}
/**
* sysfs_delete_link - remove symlink in object's directory.
* @kobj: object we're acting for.
* @targ: object we're pointing to.
* @name: name of the symlink to remove.
*
* Unlike sysfs_remove_link sysfs_delete_link has enough information
* to successfully delete symlinks in tagged directories.
*/
void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
const char *name)
{
const void *ns = NULL;
/*
* We don't own @target and it may be removed at any time.
* Synchronize using sysfs_symlink_target_lock. See
* sysfs_remove_dir() for details.
*/
spin_lock(&sysfs_symlink_target_lock);
if (targ->sd && kernfs_ns_enabled(kobj->sd))
ns = targ->sd->ns;
spin_unlock(&sysfs_symlink_target_lock);
kernfs_remove_by_name_ns(kobj->sd, name, ns);
}
/**
* sysfs_remove_link - remove symlink in object's directory.
* @kobj: object we're acting for.
* @name: name of the symlink to remove.
*/
void sysfs_remove_link(struct kobject *kobj, const char *name)
{
struct kernfs_node *parent = NULL;
if (!kobj)
parent = sysfs_root_kn;
else
parent = kobj->sd;
kernfs_remove_by_name(parent, name);
}
EXPORT_SYMBOL_GPL(sysfs_remove_link);
/**
* sysfs_rename_link_ns - rename symlink in object's directory.
* @kobj: object we're acting for.
* @targ: object we're pointing to.
* @old: previous name of the symlink.
* @new: new name of the symlink.
* @new_ns: new namespace of the symlink.
*
* A helper function for the common rename symlink idiom.
*/
int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
const char *old, const char *new, const void *new_ns)
{
struct kernfs_node *parent, *kn = NULL;
const void *old_ns = NULL;
int result;
if (!kobj)
parent = sysfs_root_kn;
else
parent = kobj->sd;
if (targ->sd)
old_ns = targ->sd->ns;
result = -ENOENT;
kn = kernfs_find_and_get_ns(parent, old, old_ns);
if (!kn)
goto out;
result = -EINVAL;
if (kernfs_type(kn) != KERNFS_LINK)
goto out;
if (kn->symlink.target_kn->priv != targ)
goto out;
result = kernfs_rename_ns(kn, parent, new, new_ns);
out:
kernfs_put(kn);
return result;
}
EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);