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 1.16 2005/03/01 10:50:48 dedekind 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 struct inode_operations jffs2_symlink_inode_operations =
  24 {
  25         .readlink =     generic_readlink,
  26         .follow_link =  jffs2_follow_link,
  27         .setattr =      jffs2_setattr
  28 };
  29
  30 static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd)
  31 {
  32         struct jffs2_inode_info *f = JFFS2_INODE_INFO(dentry->d_inode);
  33         char *p = (char *)f->dents;
  34
  35         /*
  36          * We don't acquire the f->sem mutex here since the only data we
  37          * use is f->dents which in case of the symlink inode points to the
  38          * symlink's target path.
  39          *
  40          * 1. If we are here the inode has already built and f->dents has
  41          * to point to the target path.
  42          * 2. Nobody uses f->dents (if the inode is symlink's inode). The
  43          * exception is inode freeing function which frees f->dents. But
  44          * it can't be called while we are here and before VFS has
  45          * stopped using our f->dents string which we provide by means of
  46          * nd_set_link() call.
  47          */
  48
  49         if (!p) {
  50                 printk(KERN_ERR "jffs2_follow_link(): can't find symlink taerget\n");
  51                 p = ERR_PTR(-EIO);
  52         } else {
  53                 D1(printk(KERN_DEBUG "jffs2_follow_link(): target path is '%s'\n", (char *) f->dents));
  54         }
  55
  56         nd_set_link(nd, p);
  57
  58         /*
  59          * We unlock the f->sem mutex but VFS will use the f->dents string. This is safe
  60          * since the only way that may cause f->dents to be changed is iput() operation.
  61          * But VFS will not use f->dents after iput() has been called.
  62          */
  63         return NULL;
  64 }
  65