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