fs/afs/mntpt.c

   1 /* mntpt.c: mountpoint management
   2  *
   3  * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 #include <linux/fs.h>
  18 #include <linux/pagemap.h>
  19 #include "volume.h"
  20 #include "vnode.h"
  21 #include "internal.h"
  22
  23
  24 static struct dentry *afs_mntpt_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *);
  25 static int afs_mntpt_open(struct inode *inode, struct file *file);
  26
  27 struct file_operations afs_mntpt_file_operations = {
  28         .open           = afs_mntpt_open,
  29 };
  30
  31 struct inode_operations afs_mntpt_inode_operations = {
  32         .lookup         = afs_mntpt_lookup,
  33         .readlink       = page_readlink,
  34         .getattr        = afs_inode_getattr,
  35 };
  36
  37 /*****************************************************************************/
  38 /*
  39  * check a symbolic link to see whether it actually encodes a mountpoint
  40  * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
  41  */
  42 int afs_mntpt_check_symlink(afs_vnode_t *vnode)
  43 {
  44         struct page *page;
  45         size_t size;
  46         char *buf;
  47         int ret;
  48
  49         _enter("{%u,%u}",vnode->fid.vnode,vnode->fid.unique);
  50
  51         /* read the contents of the symlink into the pagecache */
  52         page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping,0,
  53                                (filler_t*)AFS_VNODE_TO_I(vnode)->i_mapping->a_ops->readpage,NULL);
  54         if (IS_ERR(page)) {
  55                 ret = PTR_ERR(page);
  56                 goto out;
  57         }
  58
  59         ret = -EIO;
  60         wait_on_page_locked(page);
  61         buf = kmap(page);
  62         if (!PageUptodate(page))
  63                 goto out_free;
  64         if (PageError(page))
  65                 goto out_free;
  66
  67         /* examine the symlink's contents */
  68         size = vnode->status.size;
  69         _debug("symlink to %*.*s",size,(int)size,buf);
  70
  71         if (size>2 &&
  72             (buf[0]=='%' || buf[0]=='#') &&
  73             buf[size-1]=='.'
  74             ) {
  75                 _debug("symlink is a mountpoint");
  76                 spin_lock(&vnode->lock);
  77                 vnode->flags |= AFS_VNODE_MOUNTPOINT;
  78                 spin_unlock(&vnode->lock);
  79         }
  80
  81         ret = 0;
  82
  83  out_free:
  84         kunmap(page);
  85         page_cache_release(page);
  86  out:
  87         _leave(" = %d",ret);
  88         return ret;
  89
  90 } /* end afs_mntpt_check_symlink() */
  91
  92 /*****************************************************************************/
  93 /*
  94  * no valid lookup procedure on this sort of dir
  95  */
  96 static struct dentry *afs_mntpt_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
  97 {
  98         return ERR_PTR(-EREMOTE);
  99 } /* end afs_mntpt_lookup() */
 100
 101 /*****************************************************************************/
 102 /*
 103  * no valid open procedure on this sort of dir
 104  */
 105 static int afs_mntpt_open(struct inode *inode, struct file *file)
 106 {
 107         return -EREMOTE;
 108 } /* end afs_mntpt_open() */