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 #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
  19 static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd);
  20
  21 const 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
  33 static 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