fs/afs/mntpt.c

   1 /* 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/fs.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/mount.h>
  18 #include <linux/namei.h>
  19 #include <linux/gfp.h>
  20 #include "internal.h"
  21
  22
  23 static struct dentry *afs_mntpt_lookup(struct inode *dir,
  24                                        struct dentry *dentry,
  25                                        struct nameidata *nd);
  26 static int afs_mntpt_open(struct inode *inode, struct file *file);
  27 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
  28 static void afs_mntpt_expiry_timed_out(struct work_struct *work);
  29
  30 const struct file_operations afs_mntpt_file_operations = {
  31         .open           = afs_mntpt_open,
  32         .llseek         = noop_llseek,
  33 };
  34
  35 const struct inode_operations afs_mntpt_inode_operations = {
  36         .lookup         = afs_mntpt_lookup,
  37         .follow_link    = afs_mntpt_follow_link,
  38         .readlink       = page_readlink,
  39         .getattr        = afs_getattr,
  40 };
  41
  42 const struct inode_operations afs_autocell_inode_operations = {
  43         .follow_link    = afs_mntpt_follow_link,
  44         .getattr        = afs_getattr,
  45 };
  46
  47 static LIST_HEAD(afs_vfsmounts);
  48 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
  49
  50 static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
  51
  52 /*
  53  * check a symbolic link to see whether it actually encodes a mountpoint
  54  * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
  55  */
  56 int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
  57 {
  58         struct page *page;
  59         size_t size;
  60         char *buf;
  61         int ret;
  62
  63         _enter("{%x:%u,%u}",
  64                vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
  65
  66         /* read the contents of the symlink into the pagecache */
  67         page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
  68                                afs_page_filler, key);
  69         if (IS_ERR(page)) {
  70                 ret = PTR_ERR(page);
  71                 goto out;
  72         }
  73
  74         ret = -EIO;
  75         if (PageError(page))
  76                 goto out_free;
  77
  78         buf = kmap(page);
  79
  80         /* examine the symlink's contents */
  81         size = vnode->status.size;
  82         _debug("symlink to %*.*s", (int) size, (int) size, buf);
  83
  84         if (size > 2 &&
  85             (buf[0] == '%' || buf[0] == '#') &&
  86             buf[size - 1] == '.'
  87             ) {
  88                 _debug("symlink is a mountpoint");
  89                 spin_lock(&vnode->lock);
  90                 set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
  91                 spin_unlock(&vnode->lock);
  92         }
  93
  94         ret = 0;
  95
  96         kunmap(page);
  97 out_free:
  98         page_cache_release(page);
  99 out:
 100         _leave(" = %d", ret);
 101         return ret;
 102 }
 103
 104 /*
 105  * no valid lookup procedure on this sort of dir
 106  */
 107 static struct dentry *afs_mntpt_lookup(struct inode *dir,
 108                                        struct dentry *dentry,
 109                                        struct nameidata *nd)
 110 {
 111         _enter("%p,%p{%p{%s},%s}",
 112                dir,
 113                dentry,
 114                dentry->d_parent,
 115                dentry->d_parent ?
 116                dentry->d_parent->d_name.name : (const unsigned char *) "",
 117                dentry->d_name.name);
 118
 119         return ERR_PTR(-EREMOTE);
 120 }
 121
 122 /*
 123  * no valid open procedure on this sort of dir
 124  */
 125 static int afs_mntpt_open(struct inode *inode, struct file *file)
 126 {
 127         _enter("%p,%p{%p{%s},%s}",
 128                inode, file,
 129                file->f_path.dentry->d_parent,
 130                file->f_path.dentry->d_parent ?
 131                file->f_path.dentry->d_parent->d_name.name :
 132                (const unsigned char *) "",
 133                file->f_path.dentry->d_name.name);
 134
 135         return -EREMOTE;
 136 }
 137
 138 /*
 139  * create a vfsmount to be automounted
 140  */
 141 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
 142 {
 143         struct afs_super_info *super;
 144         struct vfsmount *mnt;
 145         struct afs_vnode *vnode;
 146         struct page *page;
 147         char *devname, *options;
 148         bool rwpath = false;
 149         int ret;
 150
 151         _enter("{%s}", mntpt->d_name.name);
 152
 153         BUG_ON(!mntpt->d_inode);
 154
 155         ret = -ENOMEM;
 156         devname = (char *) get_zeroed_page(GFP_KERNEL);
 157         if (!devname)
 158                 goto error_no_devname;
 159
 160         options = (char *) get_zeroed_page(GFP_KERNEL);
 161         if (!options)
 162                 goto error_no_options;
 163
 164         vnode = AFS_FS_I(mntpt->d_inode);
 165         if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
 166                 /* if the directory is a pseudo directory, use the d_name */
 167                 static const char afs_root_cell[] = ":root.cell.";
 168                 unsigned size = mntpt->d_name.len;
 169
 170                 ret = -ENOENT;
 171                 if (size < 2 || size > AFS_MAXCELLNAME)
 172                         goto error_no_page;
 173
 174                 if (mntpt->d_name.name[0] == '.') {
 175                         devname[0] = '#';
 176                         memcpy(devname + 1, mntpt->d_name.name, size - 1);
 177                         memcpy(devname + size, afs_root_cell,
 178                                sizeof(afs_root_cell));
 179                         rwpath = true;
 180                 } else {
 181                         devname[0] = '%';
 182                         memcpy(devname + 1, mntpt->d_name.name, size);
 183                         memcpy(devname + size + 1, afs_root_cell,
 184                                sizeof(afs_root_cell));
 185                 }
 186         } else {
 187                 /* read the contents of the AFS special symlink */
 188                 loff_t size = i_size_read(mntpt->d_inode);
 189                 char *buf;
 190
 191                 ret = -EINVAL;
 192                 if (size > PAGE_SIZE - 1)
 193                         goto error_no_page;
 194
 195                 page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
 196                 if (IS_ERR(page)) {
 197                         ret = PTR_ERR(page);
 198                         goto error_no_page;
 199                 }
 200
 201                 ret = -EIO;
 202                 if (PageError(page))
 203                         goto error;
 204
 205                 buf = kmap_atomic(page, KM_USER0);
 206                 memcpy(devname, buf, size);
 207                 kunmap_atomic(buf, KM_USER0);
 208                 page_cache_release(page);
 209                 page = NULL;
 210         }
 211
 212         /* work out what options we want */
 213         super = AFS_FS_S(mntpt->d_sb);
 214         memcpy(options, "cell=", 5);
 215         strcpy(options + 5, super->volume->cell->name);
 216         if (super->volume->type == AFSVL_RWVOL || rwpath)
 217                 strcat(options, ",rwpath");
 218
 219         /* try and do the mount */
 220         _debug("--- attempting mount %s -o %s ---", devname, options);
 221         mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
 222         _debug("--- mount result %p ---", mnt);
 223
 224         free_page((unsigned long) devname);
 225         free_page((unsigned long) options);
 226         _leave(" = %p", mnt);
 227         return mnt;
 228
 229 error:
 230         page_cache_release(page);
 231 error_no_page:
 232         free_page((unsigned long) options);
 233 error_no_options:
 234         free_page((unsigned long) devname);
 235 error_no_devname:
 236         _leave(" = %d", ret);
 237         return ERR_PTR(ret);
 238 }
 239
 240 /*
 241  * follow a link from a mountpoint directory, thus causing it to be mounted
 242  */
 243 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
 244 {
 245         struct vfsmount *newmnt;
 246         int err;
 247
 248         _enter("%p{%s},{%s:%p{%s},}",
 249                dentry,
 250                dentry->d_name.name,
 251                nd->path.mnt->mnt_devname,
 252                dentry,
 253                nd->path.dentry->d_name.name);
 254
 255         dput(nd->path.dentry);
 256         nd->path.dentry = dget(dentry);
 257
 258         newmnt = afs_mntpt_do_automount(nd->path.dentry);
 259         if (IS_ERR(newmnt)) {
 260                 path_put(&nd->path);
 261                 return (void *)newmnt;
 262         }
 263
 264         mntget(newmnt);
 265         err = do_add_mount(newmnt, &nd->path, MNT_SHRINKABLE, &afs_vfsmounts);
 266         switch (err) {
 267         case 0:
 268                 path_put(&nd->path);
 269                 nd->path.mnt = newmnt;
 270                 nd->path.dentry = dget(newmnt->mnt_root);
 271                 schedule_delayed_work(&afs_mntpt_expiry_timer,
 272                                       afs_mntpt_expiry_timeout * HZ);
 273                 break;
 274         case -EBUSY:
 275                 /* someone else made a mount here whilst we were busy */
 276                 while (d_mountpoint(nd->path.dentry) &&
 277                        follow_down(&nd->path))
 278                         ;
 279                 err = 0;
 280         default:
 281                 mntput(newmnt);
 282                 break;
 283         }
 284
 285         _leave(" = %d", err);
 286         return ERR_PTR(err);
 287 }
 288
 289 /*
 290  * handle mountpoint expiry timer going off
 291  */
 292 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
 293 {
 294         _enter("");
 295
 296         if (!list_empty(&afs_vfsmounts)) {
 297                 mark_mounts_for_expiry(&afs_vfsmounts);
 298                 schedule_delayed_work(&afs_mntpt_expiry_timer,
 299                                       afs_mntpt_expiry_timeout * HZ);
 300         }
 301
 302         _leave("");
 303 }
 304
 305 /*
 306  * kill the AFS mountpoint timer if it's still running
 307  */
 308 void afs_mntpt_kill_timer(void)
 309 {
 310         _enter("");
 311
 312         ASSERT(list_empty(&afs_vfsmounts));
 313         cancel_delayed_work(&afs_mntpt_expiry_timer);
 314         flush_scheduled_work();
 315 }