LXR linux/fs/jffs2/symlink.c

   1/*
   2 * JFFS2 -- Journalling Flash File System, Version 2.
   3 *
   4 * Copyright Â© 2001-2007 Red Hat, Inc.
   5 *
   6 * Created by David Woodhouse <dwmw2@infradead.org>
   7 *
   8 * For licensing information, see the file 'LICENCE' in this directory.
   9 *
  10 */
  11
  12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14#include <linux/kernel.h>
  15#include <linux/fs.h>
  16#include <linux/namei.h>
  17#include "nodelist.h"
  18
  19static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd);
  20
  21const struct inode_operations jffs2_symlink_inode_operations =
  22{
  23        .readlink =     generic_readlink,
  24        .follow_link =  jffs2_follow_link,
  25        .get_acl =      jffs2_get_acl,
  26        .setattr =      jffs2_setattr,
  27        .setxattr =     jffs2_setxattr,
  28        .getxattr =     jffs2_getxattr,
  29        .listxattr =    jffs2_listxattr,
  30        .removexattr =  jffs2_removexattr
  31};
  32
  33static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd)
  34{
  35        struct jffs2_inode_info *f = JFFS2_INODE_INFO(dentry->d_inode);
  36        char *p = (char *)f->target;
  37
  38        /*
  39         * We don't acquire the f->sem mutex here since the only data we
  40         * use is f->target.
  41         *
  42         * 1. If we are here the inode has already built and f->target has
  43         * to point to the target path.
  44         * 2. Nobody uses f->target (if the inode is symlink's inode). The
  45         * exception is inode freeing function which frees f->target. But
  46         * it can't be called while we are here and before VFS has
  47         * stopped using our f->target string which we provide by means of
  48         * nd_set_link() call.
  49         */
  50
  51        if (!p) {
  52                pr_err("%s(): can't find symlink target\n", __func__);
  53                p = ERR_PTR(-EIO);
  54        }
  55        jffs2_dbg(1, "%s(): target path is '%s'\n",
  56                  __func__, (char *)f->target);
  57
  58        nd_set_link(nd, p);
  59
  60        /*
  61         * We will unlock the f->sem mutex but VFS will use the f->target string. This is safe
  62         * since the only way that may cause f->target to be changed is iput() operation.
  63         * But VFS will not use f->target after iput() has been called.
  64         */
  65        return NULL;
  66}
  67
  68