fs/jffs2/symlink.c

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