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/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         filler_t *filler;
  67         size_t size;
  68         char *buf;
  69         int ret;
  70
  71         _enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique);
  72
  73         /* read the contents of the symlink into the pagecache */
  74         filler = (filler_t *) AFS_VNODE_TO_I(vnode)->i_mapping->a_ops->readpage;
  75
  76         page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
  77                                filler, NULL);
  78         if (IS_ERR(page)) {
  79                 ret = PTR_ERR(page);
  80                 goto out;
  81         }
  82
  83         ret = -EIO;
  84         wait_on_page_locked(page);
  85         buf = kmap(page);
  86         if (!PageUptodate(page))
  87                 goto out_free;
  88         if (PageError(page))
  89                 goto out_free;
  90
  91         /* examine the symlink's contents */
  92         size = vnode->status.size;
  93         _debug("symlink to %*.*s", size, (int) size, buf);
  94
  95         if (size > 2 &&
  96             (buf[0] == '%' || buf[0] == '#') &&
  97             buf[size - 1] == '.'
  98             ) {
  99                 _debug("symlink is a mountpoint");
 100                 spin_lock(&vnode->lock);
 101                 vnode->flags |= AFS_VNODE_MOUNTPOINT;
 102                 spin_unlock(&vnode->lock);
 103         }
 104
 105         ret = 0;
 106
 107  out_free:
 108         kunmap(page);
 109         page_cache_release(page);
 110  out:
 111         _leave(" = %d", ret);
 112         return ret;
 113
 114 } /* end afs_mntpt_check_symlink() */
 115
 116 /*****************************************************************************/
 117 /*
 118  * no valid lookup procedure on this sort of dir
 119  */
 120 static struct dentry *afs_mntpt_lookup(struct inode *dir,
 121                                        struct dentry *dentry,
 122                                        struct nameidata *nd)
 123 {
 124         kenter("%p,%p{%p{%s},%s}",
 125                dir,
 126                dentry,
 127                dentry->d_parent,
 128                dentry->d_parent ?
 129                dentry->d_parent->d_name.name : (const unsigned char *) "",
 130                dentry->d_name.name);
 131
 132         return ERR_PTR(-EREMOTE);
 133 } /* end afs_mntpt_lookup() */
 134
 135 /*****************************************************************************/
 136 /*
 137  * no valid open procedure on this sort of dir
 138  */
 139 static int afs_mntpt_open(struct inode *inode, struct file *file)
 140 {
 141         kenter("%p,%p{%p{%s},%s}",
 142                inode, file,
 143                file->f_dentry->d_parent,
 144                file->f_dentry->d_parent ?
 145                file->f_dentry->d_parent->d_name.name :
 146                (const unsigned char *) "",
 147                file->f_dentry->d_name.name);
 148
 149         return -EREMOTE;
 150 } /* end afs_mntpt_open() */
 151
 152 /*****************************************************************************/
 153 /*
 154  * create a vfsmount to be automounted
 155  */
 156 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
 157 {
 158         struct afs_super_info *super;
 159         struct vfsmount *mnt;
 160         struct page *page = NULL;
 161         size_t size;
 162         char *buf, *devname = NULL, *options = NULL;
 163         filler_t *filler;
 164         int ret;
 165
 166         kenter("{%s}", mntpt->d_name.name);
 167
 168         BUG_ON(!mntpt->d_inode);
 169
 170         ret = -EINVAL;
 171         size = mntpt->d_inode->i_size;
 172         if (size > PAGE_SIZE - 1)
 173                 goto error;
 174
 175         ret = -ENOMEM;
 176         devname = (char *) get_zeroed_page(GFP_KERNEL);
 177         if (!devname)
 178                 goto error;
 179
 180         options = (char *) get_zeroed_page(GFP_KERNEL);
 181         if (!options)
 182                 goto error;
 183
 184         /* read the contents of the AFS special symlink */
 185         filler = (filler_t *)mntpt->d_inode->i_mapping->a_ops->readpage;
 186
 187         page = read_cache_page(mntpt->d_inode->i_mapping, 0, filler, NULL);
 188         if (IS_ERR(page)) {
 189                 ret = PTR_ERR(page);
 190                 goto error;
 191         }
 192
 193         ret = -EIO;
 194         wait_on_page_locked(page);
 195         if (!PageUptodate(page) || PageError(page))
 196                 goto error;
 197
 198         buf = kmap(page);
 199         memcpy(devname, buf, size);
 200         kunmap(page);
 201         page_cache_release(page);
 202         page = NULL;
 203
 204         /* work out what options we want */
 205         super = AFS_FS_S(mntpt->d_sb);
 206         memcpy(options, "cell=", 5);
 207         strcpy(options + 5, super->volume->cell->name);
 208         if (super->volume->type == AFSVL_RWVOL)
 209                 strcat(options, ",rwpath");
 210
 211         /* try and do the mount */
 212         kdebug("--- attempting mount %s -o %s ---", devname, options);
 213         mnt = do_kern_mount("afs", 0, devname, options);
 214         kdebug("--- mount result %p ---", mnt);
 215
 216         free_page((unsigned long) devname);
 217         free_page((unsigned long) options);
 218         kleave(" = %p", mnt);
 219         return mnt;
 220
 221  error:
 222         if (page)
 223                 page_cache_release(page);
 224         if (devname)
 225                 free_page((unsigned long) devname);
 226         if (options)
 227                 free_page((unsigned long) options);
 228         kleave(" = %d", ret);
 229         return ERR_PTR(ret);
 230 } /* end afs_mntpt_do_automount() */
 231
 232 /*****************************************************************************/
 233 /*
 234  * follow a link from a mountpoint directory, thus causing it to be mounted
 235  */
 236 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
 237 {
 238         struct vfsmount *newmnt;
 239         struct dentry *old_dentry;
 240         int err;
 241
 242         kenter("%p{%s},{%s:%p{%s}}",
 243                dentry,
 244                dentry->d_name.name,
 245                nd->mnt->mnt_devname,
 246                dentry,
 247                nd->dentry->d_name.name);
 248
 249         newmnt = afs_mntpt_do_automount(dentry);
 250         if (IS_ERR(newmnt)) {
 251                 path_release(nd);
 252                 return (void *)newmnt;
 253         }
 254
 255         old_dentry = nd->dentry;
 256         nd->dentry = dentry;
 257         err = do_add_mount(newmnt, nd, 0, &afs_vfsmounts);
 258         nd->dentry = old_dentry;
 259
 260         path_release(nd);
 261
 262         if (!err) {
 263                 mntget(newmnt);
 264                 nd->mnt = newmnt;
 265                 dget(newmnt->mnt_root);
 266                 nd->dentry = newmnt->mnt_root;
 267         }
 268
 269         kleave(" = %d", err);
 270         return ERR_PTR(err);
 271 } /* end afs_mntpt_follow_link() */
 272
 273 /*****************************************************************************/
 274 /*
 275  * handle mountpoint expiry timer going off
 276  */
 277 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer)
 278 {
 279         kenter("");
 280
 281         mark_mounts_for_expiry(&afs_vfsmounts);
 282
 283         afs_kafstimod_add_timer(&afs_mntpt_expiry_timer,
 284                                 afs_mntpt_expiry_timeout * HZ);
 285
 286         kleave("");
 287 } /* end afs_mntpt_expiry_timed_out() */