linux/fs/afs/mntpt.c
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   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
  23static struct dentry *afs_mntpt_lookup(struct inode *dir,
  24                                       struct dentry *dentry,
  25                                       unsigned int flags);
  26static int afs_mntpt_open(struct inode *inode, struct file *file);
  27static void afs_mntpt_expiry_timed_out(struct work_struct *work);
  28
  29const struct file_operations afs_mntpt_file_operations = {
  30        .open           = afs_mntpt_open,
  31        .llseek         = noop_llseek,
  32};
  33
  34const struct inode_operations afs_mntpt_inode_operations = {
  35        .lookup         = afs_mntpt_lookup,
  36        .readlink       = page_readlink,
  37        .getattr        = afs_getattr,
  38};
  39
  40const struct inode_operations afs_autocell_inode_operations = {
  41        .getattr        = afs_getattr,
  42};
  43
  44static LIST_HEAD(afs_vfsmounts);
  45static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
  46
  47static 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 */
  53int 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);
  95out_free:
  96        page_cache_release(page);
  97out:
  98        _leave(" = %d", ret);
  99        return ret;
 100}
 101
 102/*
 103 * no valid lookup procedure on this sort of dir
 104 */
 105static 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 */
 123static 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 */
 139static 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
 227error:
 228        page_cache_release(page);
 229error_no_page:
 230        free_page((unsigned long) options);
 231error_no_options:
 232        free_page((unsigned long) devname);
 233error_no_devname:
 234        _leave(" = %d", ret);
 235        return ERR_PTR(ret);
 236}
 237
 238/*
 239 * handle an automount point
 240 */
 241struct 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 */
 262static 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 */
 278void 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}
 285
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