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 <linux/mount.h>
  20 #include <linux/namei.h>
  21 #include <linux/mnt_namespace.h>
  22 #include "super.h"
  23 #include "cell.h"
  24 #include "volume.h"
  25 #include "vnode.h"
  26 #include "internal.h"
  27
  28
  29 static struct dentry *afs_mntpt_lookup(struct inode *dir,
  30                                        struct dentry *dentry,
  31                                        struct nameidata *nd);
  32 static int afs_mntpt_open(struct inode *inode, struct file *file);
  33 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
  34
  35 const struct file_operations afs_mntpt_file_operations = {
  36         .open           = afs_mntpt_open,
  37 };
  38
  39 struct inode_operations afs_mntpt_inode_operations = {
  40         .lookup         = afs_mntpt_lookup,
  41         .follow_link    = afs_mntpt_follow_link,
  42         .readlink       = page_readlink,
  43         .getattr        = afs_inode_getattr,
  44 };
  45
  46 static LIST_HEAD(afs_vfsmounts);
  47
  48 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer);
  49
  50 struct afs_timer_ops afs_mntpt_expiry_timer_ops = {
  51         .timed_out      = afs_mntpt_expiry_timed_out,
  52 };
  53
  54 struct afs_timer afs_mntpt_expiry_timer;
  55
  56 unsigned long afs_mntpt_expiry_timeout = 20;
  57
  58 /*****************************************************************************/
  59 /*
  60  * check a symbolic link to see whether it actually encodes a mountpoint
  61  * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
  62  */
  63 int afs_mntpt_check_symlink(struct afs_vnode *vnode)
  64 {
  65         struct page *page;
  66         size_t size;
  67         char *buf;
  68         int ret;
  69
  70         _enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique);
  71
  72         /* read the contents of the symlink into the pagecache */
  73         page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, NULL);
  74         if (IS_ERR(page)) {
  75                 ret = PTR_ERR(page);
  76                 goto out;
  77         }
  78
  79         ret = -EIO;
  80         wait_on_page_locked(page);
  81         buf = kmap(page);
  82         if (!PageUptodate(page))
  83                 goto out_free;
  84         if (PageError(page))
  85                 goto out_free;
  86
  87         /* examine the symlink's contents */
  88         size = vnode->status.size;
  89         _debug("symlink to %*.*s", size, (int) size, buf);
  90
  91         if (size > 2 &&
  92             (buf[0] == '%' || buf[0] == '#') &&
  93             buf[size - 1] == '.'
  94             ) {
  95                 _debug("symlink is a mountpoint");
  96                 spin_lock(&vnode->lock);
  97                 vnode->flags |= AFS_VNODE_MOUNTPOINT;
  98                 spin_unlock(&vnode->lock);
  99         }
 100
 101         ret = 0;
 102
 103  out_free:
 104         kunmap(page);
 105         page_cache_release(page);
 106  out:
 107         _leave(" = %d", ret);
 108         return ret;
 109
 110 } /* end afs_mntpt_check_symlink() */
 111
 112 /*****************************************************************************/
 113 /*
 114  * no valid lookup procedure on this sort of dir
 115  */
 116 static struct dentry *afs_mntpt_lookup(struct inode *dir,
 117                                        struct dentry *dentry,
 118                                        struct nameidata *nd)
 119 {
 120         kenter("%p,%p{%p{%s},%s}",
 121                dir,
 122                dentry,
 123                dentry->d_parent,
 124                dentry->d_parent ?
 125                dentry->d_parent->d_name.name : (const unsigned char *) "",
 126                dentry->d_name.name);
 127
 128         return ERR_PTR(-EREMOTE);
 129 } /* end afs_mntpt_lookup() */
 130
 131 /*****************************************************************************/
 132 /*
 133  * no valid open procedure on this sort of dir
 134  */
 135 static int afs_mntpt_open(struct inode *inode, struct file *file)
 136 {
 137         kenter("%p,%p{%p{%s},%s}",
 138                inode, file,
 139                file->f_path.dentry->d_parent,
 140                file->f_path.dentry->d_parent ?
 141                file->f_path.dentry->d_parent->d_name.name :
 142                (const unsigned char *) "",
 143                file->f_path.dentry->d_name.name);
 144
 145         return -EREMOTE;
 146 } /* end afs_mntpt_open() */
 147
 148 /*****************************************************************************/
 149 /*
 150  * create a vfsmount to be automounted
 151  */
 152 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
 153 {
 154         struct afs_super_info *super;
 155         struct vfsmount *mnt;
 156         struct page *page = NULL;
 157         size_t size;
 158         char *buf, *devname = NULL, *options = NULL;
 159         int ret;
 160
 161         kenter("{%s}", mntpt->d_name.name);
 162
 163         BUG_ON(!mntpt->d_inode);
 164
 165         ret = -EINVAL;
 166         size = mntpt->d_inode->i_size;
 167         if (size > PAGE_SIZE - 1)
 168                 goto error;
 169
 170         ret = -ENOMEM;
 171         devname = (char *) get_zeroed_page(GFP_KERNEL);
 172         if (!devname)
 173                 goto error;
 174
 175         options = (char *) get_zeroed_page(GFP_KERNEL);
 176         if (!options)
 177                 goto error;
 178
 179         /* read the contents of the AFS special symlink */
 180         page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
 181         if (IS_ERR(page)) {
 182                 ret = PTR_ERR(page);
 183                 goto error;
 184         }
 185
 186         ret = -EIO;
 187         wait_on_page_locked(page);
 188         if (!PageUptodate(page) || PageError(page))
 189                 goto error;
 190
 191         buf = kmap(page);
 192         memcpy(devname, buf, size);
 193         kunmap(page);
 194         page_cache_release(page);
 195         page = NULL;
 196
 197         /* work out what options we want */
 198         super = AFS_FS_S(mntpt->d_sb);
 199         memcpy(options, "cell=", 5);
 200         strcpy(options + 5, super->volume->cell->name);
 201         if (super->volume->type == AFSVL_RWVOL)
 202                 strcat(options, ",rwpath");
 203
 204         /* try and do the mount */
 205         kdebug("--- attempting mount %s -o %s ---", devname, options);
 206         mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
 207         kdebug("--- mount result %p ---", mnt);
 208
 209         free_page((unsigned long) devname);
 210         free_page((unsigned long) options);
 211         kleave(" = %p", mnt);
 212         return mnt;
 213
 214  error:
 215         if (page)
 216                 page_cache_release(page);
 217         if (devname)
 218                 free_page((unsigned long) devname);
 219         if (options)
 220                 free_page((unsigned long) options);
 221         kleave(" = %d", ret);
 222         return ERR_PTR(ret);
 223 } /* end afs_mntpt_do_automount() */
 224
 225 /*****************************************************************************/
 226 /*
 227  * follow a link from a mountpoint directory, thus causing it to be mounted
 228  */
 229 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
 230 {
 231         struct vfsmount *newmnt;
 232         struct dentry *old_dentry;
 233         int err;
 234
 235         kenter("%p{%s},{%s:%p{%s}}",
 236                dentry,
 237                dentry->d_name.name,
 238                nd->mnt->mnt_devname,
 239                dentry,
 240                nd->dentry->d_name.name);
 241
 242         newmnt = afs_mntpt_do_automount(dentry);
 243         if (IS_ERR(newmnt)) {
 244                 path_release(nd);
 245                 return (void *)newmnt;
 246         }
 247
 248         old_dentry = nd->dentry;
 249         nd->dentry = dentry;
 250         err = do_add_mount(newmnt, nd, 0, &afs_vfsmounts);
 251         nd->dentry = old_dentry;
 252
 253         path_release(nd);
 254
 255         if (!err) {
 256                 mntget(newmnt);
 257                 nd->mnt = newmnt;
 258                 dget(newmnt->mnt_root);
 259                 nd->dentry = newmnt->mnt_root;
 260         }
 261
 262         kleave(" = %d", err);
 263         return ERR_PTR(err);
 264 } /* end afs_mntpt_follow_link() */
 265
 266 /*****************************************************************************/
 267 /*
 268  * handle mountpoint expiry timer going off
 269  */
 270 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer)
 271 {
 272         kenter("");
 273
 274         mark_mounts_for_expiry(&afs_vfsmounts);
 275
 276         afs_kafstimod_add_timer(&afs_mntpt_expiry_timer,
 277                                 afs_mntpt_expiry_timeout * HZ);
 278
 279         kleave("");
 280 } /* end afs_mntpt_expiry_timed_out() */