294 строки
6.7 KiB
C
294 строки
6.7 KiB
C
/*
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* fs/sysfs/symlink.c - sysfs symlink implementation
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#include <linux/fs.h>
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#include <linux/gfp.h>
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#include <linux/mount.h>
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/namei.h>
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#include <linux/mutex.h>
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#include <linux/security.h>
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#include "sysfs.h"
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static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
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const char *name, int warn)
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{
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struct sysfs_dirent *parent_sd = NULL;
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struct sysfs_dirent *target_sd = NULL;
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struct sysfs_dirent *sd = NULL;
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struct sysfs_addrm_cxt acxt;
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int error;
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BUG_ON(!name);
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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error = -EFAULT;
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if (!parent_sd)
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goto out_put;
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/* target->sd can go away beneath us but is protected with
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* sysfs_assoc_lock. Fetch target_sd from it.
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*/
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spin_lock(&sysfs_assoc_lock);
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if (target->sd)
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target_sd = sysfs_get(target->sd);
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spin_unlock(&sysfs_assoc_lock);
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error = -ENOENT;
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if (!target_sd)
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goto out_put;
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error = -ENOMEM;
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sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
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if (!sd)
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goto out_put;
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if (sysfs_ns_type(parent_sd))
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sd->s_ns = target->ktype->namespace(target);
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sd->s_symlink.target_sd = target_sd;
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target_sd = NULL; /* reference is now owned by the symlink */
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sysfs_addrm_start(&acxt, parent_sd);
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if (warn)
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error = sysfs_add_one(&acxt, sd);
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else
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error = __sysfs_add_one(&acxt, sd);
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sysfs_addrm_finish(&acxt);
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if (error)
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goto out_put;
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return 0;
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out_put:
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sysfs_put(target_sd);
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sysfs_put(sd);
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return error;
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}
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/**
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* sysfs_create_link - create symlink between two objects.
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* @kobj: object whose directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*/
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int sysfs_create_link(struct kobject *kobj, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link(kobj, target, name, 1);
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}
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/**
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* sysfs_create_link_nowarn - create symlink between two objects.
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* @kobj: object whose directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*
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* This function does the same as sysf_create_link(), but it
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* doesn't warn if the link already exists.
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*/
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int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link(kobj, target, name, 0);
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}
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/**
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* sysfs_delete_link - remove symlink in object's directory.
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* @kobj: object we're acting for.
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* @targ: object we're pointing to.
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* @name: name of the symlink to remove.
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*
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* Unlike sysfs_remove_link sysfs_delete_link has enough information
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* to successfully delete symlinks in tagged directories.
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*/
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void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
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const char *name)
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{
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const void *ns = NULL;
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spin_lock(&sysfs_assoc_lock);
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if (targ->sd)
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ns = targ->sd->s_ns;
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spin_unlock(&sysfs_assoc_lock);
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sysfs_hash_and_remove(kobj->sd, ns, name);
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}
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/**
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* sysfs_remove_link - remove symlink in object's directory.
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* @kobj: object we're acting for.
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* @name: name of the symlink to remove.
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*/
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void sysfs_remove_link(struct kobject * kobj, const char * name)
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{
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struct sysfs_dirent *parent_sd = NULL;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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sysfs_hash_and_remove(parent_sd, NULL, name);
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}
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/**
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* sysfs_rename_link - rename symlink in object's directory.
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* @kobj: object we're acting for.
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* @targ: object we're pointing to.
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* @old: previous name of the symlink.
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* @new: new name of the symlink.
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*
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* A helper function for the common rename symlink idiom.
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*/
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int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
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const char *old, const char *new)
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{
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struct sysfs_dirent *parent_sd, *sd = NULL;
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const void *old_ns = NULL, *new_ns = NULL;
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int result;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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if (targ->sd)
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old_ns = targ->sd->s_ns;
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result = -ENOENT;
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sd = sysfs_get_dirent(parent_sd, old_ns, old);
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if (!sd)
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goto out;
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result = -EINVAL;
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if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
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goto out;
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if (sd->s_symlink.target_sd->s_dir.kobj != targ)
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goto out;
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if (sysfs_ns_type(parent_sd))
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new_ns = targ->ktype->namespace(targ);
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result = sysfs_rename(sd, parent_sd, new_ns, new);
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out:
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sysfs_put(sd);
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return result;
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}
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static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
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struct sysfs_dirent *target_sd, char *path)
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{
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struct sysfs_dirent *base, *sd;
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char *s = path;
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int len = 0;
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/* go up to the root, stop at the base */
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base = parent_sd;
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while (base->s_parent) {
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sd = target_sd->s_parent;
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while (sd->s_parent && base != sd)
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sd = sd->s_parent;
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if (base == sd)
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break;
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strcpy(s, "../");
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s += 3;
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base = base->s_parent;
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}
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/* determine end of target string for reverse fillup */
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sd = target_sd;
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while (sd->s_parent && sd != base) {
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len += strlen(sd->s_name) + 1;
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sd = sd->s_parent;
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}
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/* check limits */
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if (len < 2)
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return -EINVAL;
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len--;
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if ((s - path) + len > PATH_MAX)
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return -ENAMETOOLONG;
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/* reverse fillup of target string from target to base */
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sd = target_sd;
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while (sd->s_parent && sd != base) {
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int slen = strlen(sd->s_name);
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len -= slen;
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strncpy(s + len, sd->s_name, slen);
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if (len)
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s[--len] = '/';
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sd = sd->s_parent;
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}
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return 0;
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}
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static int sysfs_getlink(struct dentry *dentry, char * path)
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{
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struct sysfs_dirent *sd = dentry->d_fsdata;
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struct sysfs_dirent *parent_sd = sd->s_parent;
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struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
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int error;
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mutex_lock(&sysfs_mutex);
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error = sysfs_get_target_path(parent_sd, target_sd, path);
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mutex_unlock(&sysfs_mutex);
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return error;
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}
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static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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int error = -ENOMEM;
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unsigned long page = get_zeroed_page(GFP_KERNEL);
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if (page) {
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error = sysfs_getlink(dentry, (char *) page);
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if (error < 0)
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free_page((unsigned long)page);
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}
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nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
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return NULL;
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}
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static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
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{
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char *page = nd_get_link(nd);
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if (!IS_ERR(page))
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free_page((unsigned long)page);
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}
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const struct inode_operations sysfs_symlink_inode_operations = {
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.setxattr = sysfs_setxattr,
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.readlink = generic_readlink,
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.follow_link = sysfs_follow_link,
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.put_link = sysfs_put_link,
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.setattr = sysfs_setattr,
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.getattr = sysfs_getattr,
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.permission = sysfs_permission,
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};
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EXPORT_SYMBOL_GPL(sysfs_create_link);
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EXPORT_SYMBOL_GPL(sysfs_remove_link);
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EXPORT_SYMBOL_GPL(sysfs_rename_link);
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