fs/jffs2/symlink.c

   1 /*
   2  * JFFS2 -- Journalling Flash File System, Version 2.
   3  *
   4  * Copyright (C) 2001, 2002 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  * $Id: symlink.c,v 1.19 2005/11/07 11:14:42 gleixner Exp $
  11  *
  12  */
  13
  14
  15 #include <linux/kernel.h>
  16 #include <linux/slab.h>
  17 #include <linux/fs.h>
  18 #include <linux/namei.h>
  19 #include "nodelist.h"
  20
  21 static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd);
  22
  23 const struct inode_operations jffs2_symlink_inode_operations =
  24 {
  25         .readlink =     generic_readlink,
  26         .follow_link =  jffs2_follow_link,
  27         .permission =   jffs2_permission,
  28         .setattr =      jffs2_setattr,
  29         .setxattr =     jffs2_setxattr,
  30         .getxattr =     jffs2_getxattr,
  31         .listxattr =    jffs2_listxattr,
  32         .removexattr =  jffs2_removexattr
  33 };
  34
  35 static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd)
  36 {
  37         struct jffs2_inode_info *f = JFFS2_INODE_INFO(dentry->d_inode);
  38         char *p = (char *)f->target;
  39
  40         /*
  41          * We don't acquire the f->sem mutex here since the only data we
  42          * use is f->target.
  43          *
  44          * 1. If we are here the inode has already built and f->target has
  45          * to point to the target path.
  46          * 2. Nobody uses f->target (if the inode is symlink's inode). The
  47          * exception is inode freeing function which frees f->target. But
  48          * it can't be called while we are here and before VFS has
  49          * stopped using our f->target string which we provide by means of
  50          * nd_set_link() call.
  51          */
  52
  53         if (!p) {
  54                 printk(KERN_ERR "jffs2_follow_link(): can't find symlink target\n");
  55                 p = ERR_PTR(-EIO);
  56         }
  57         D1(printk(KERN_DEBUG "jffs2_follow_link(): target path is '%s'\n", (char *) f->target));
  58
  59         nd_set_link(nd, p);
  60
  61         /*
  62          * We will unlock the f->sem mutex but VFS will use the f->target string. This is safe
  63          * since the only way that may cause f->target to be changed is iput() operation.
  64          * But VFS will not use f->target after iput() has been called.
  65          */
  66         return NULL;
  67 }
  68