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