/* mountpoint management

   *
   * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>

  #include <linux/slab.h>
  #include <linux/fs.h>
  #include <linux/pagemap.h>
  #include <linux/mount.h>
  #include <linux/namei.h>

  #include <linux/mnt_namespace.h>

  #include "internal.h"
  
  
  static struct dentry *afs_mntpt_lookup(struct inode *dir,
  				       struct dentry *dentry,
  				       struct nameidata *nd);
  static int afs_mntpt_open(struct inode *inode, struct file *file);

  static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);

  static void afs_mntpt_expiry_timed_out(struct work_struct *work);

  const struct file_operations afs_mntpt_file_operations = {

  	.open		= afs_mntpt_open,
  };

  const struct inode_operations afs_mntpt_inode_operations = {

  	.lookup		= afs_mntpt_lookup,
  	.follow_link	= afs_mntpt_follow_link,
  	.readlink	= page_readlink,

  	.getattr	= afs_getattr,

  };
  
  static LIST_HEAD(afs_vfsmounts);

  static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);

  unsigned long afs_mntpt_expiry_timeout = 10 * 60;

  /*
   * check a symbolic link to see whether it actually encodes a mountpoint
   * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
   */

  int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)

  {

  	struct file file = {
  		.private_data = key,
  	};

  	struct page *page;

  	size_t size;
  	char *buf;
  	int ret;

  	_enter("{%x:%u,%u}",
  	       vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);

  
  	/* read the contents of the symlink into the pagecache */

  	page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, &file);

  	if (IS_ERR(page)) {
  		ret = PTR_ERR(page);
  		goto out;
  	}
  
  	ret = -EIO;

  	if (PageError(page))
  		goto out_free;

  	buf = kmap(page);

  	/* examine the symlink's contents */
  	size = vnode->status.size;

  	_debug("symlink to %*.*s", (int) size, (int) size, buf);

  
  	if (size > 2 &&
  	    (buf[0] == '%' || buf[0] == '#') &&
  	    buf[size - 1] == '.'
  	    ) {
  		_debug("symlink is a mountpoint");
  		spin_lock(&vnode->lock);

  		set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);

  		spin_unlock(&vnode->lock);
  	}
  
  	ret = 0;

  	kunmap(page);

  out_free:

  	page_cache_release(page);

  out:

  	_leave(" = %d", ret);
  	return ret;

  }

  /*
   * no valid lookup procedure on this sort of dir
   */
  static struct dentry *afs_mntpt_lookup(struct inode *dir,
  				       struct dentry *dentry,
  				       struct nameidata *nd)
  {

  	_enter("%p,%p{%p{%s},%s}",

  	       dir,
  	       dentry,
  	       dentry->d_parent,
  	       dentry->d_parent ?
  	       dentry->d_parent->d_name.name : (const unsigned char *) "",
  	       dentry->d_name.name);
  
  	return ERR_PTR(-EREMOTE);

  }

  /*
   * no valid open procedure on this sort of dir
   */
  static int afs_mntpt_open(struct inode *inode, struct file *file)
  {

  	_enter("%p,%p{%p{%s},%s}",

  	       inode, file,

  	       file->f_path.dentry->d_parent,
  	       file->f_path.dentry->d_parent ?
  	       file->f_path.dentry->d_parent->d_name.name :

  	       (const unsigned char *) "",

  	       file->f_path.dentry->d_name.name);

  
  	return -EREMOTE;

  }

  /*
   * create a vfsmount to be automounted
   */
  static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
  {
  	struct afs_super_info *super;
  	struct vfsmount *mnt;
  	struct page *page = NULL;
  	size_t size;
  	char *buf, *devname = NULL, *options = NULL;

  	int ret;

  	_enter("{%s}", mntpt->d_name.name);

  
  	BUG_ON(!mntpt->d_inode);
  
  	ret = -EINVAL;
  	size = mntpt->d_inode->i_size;
  	if (size > PAGE_SIZE - 1)
  		goto error;
  
  	ret = -ENOMEM;
  	devname = (char *) get_zeroed_page(GFP_KERNEL);
  	if (!devname)
  		goto error;
  
  	options = (char *) get_zeroed_page(GFP_KERNEL);
  	if (!options)
  		goto error;
  
  	/* read the contents of the AFS special symlink */

  	page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);

  	if (IS_ERR(page)) {
  		ret = PTR_ERR(page);
  		goto error;
  	}
  
  	ret = -EIO;

  	if (PageError(page))

  		goto error;
  
  	buf = kmap(page);
  	memcpy(devname, buf, size);
  	kunmap(page);
  	page_cache_release(page);
  	page = NULL;
  
  	/* work out what options we want */
  	super = AFS_FS_S(mntpt->d_sb);
  	memcpy(options, "cell=", 5);
  	strcpy(options + 5, super->volume->cell->name);
  	if (super->volume->type == AFSVL_RWVOL)
  		strcat(options, ",rwpath");
  
  	/* try and do the mount */

  	_debug("--- attempting mount %s -o %s ---", devname, options);

  	mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);

  	_debug("--- mount result %p ---", mnt);

  
  	free_page((unsigned long) devname);
  	free_page((unsigned long) options);

  	_leave(" = %p", mnt);

  	return mnt;

  error:

  	if (page)
  		page_cache_release(page);
  	if (devname)
  		free_page((unsigned long) devname);
  	if (options)
  		free_page((unsigned long) options);

  	_leave(" = %d", ret);

  	return ERR_PTR(ret);

  }

  /*
   * follow a link from a mountpoint directory, thus causing it to be mounted
   */

  static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)

  {
  	struct vfsmount *newmnt;

  	int err;

  	_enter("%p{%s},{%s:%p{%s},}",

  	       dentry,
  	       dentry->d_name.name,
  	       nd->mnt->mnt_devname,
  	       dentry,
  	       nd->dentry->d_name.name);

  	dput(nd->dentry);
  	nd->dentry = dget(dentry);
  
  	newmnt = afs_mntpt_do_automount(nd->dentry);

  	if (IS_ERR(newmnt)) {
  		path_release(nd);

  		return (void *)newmnt;

  	}

  	mntget(newmnt);
  	err = do_add_mount(newmnt, nd, MNT_SHRINKABLE, &afs_vfsmounts);
  	switch (err) {
  	case 0:

  		mntput(nd->mnt);
  		dput(nd->dentry);

  		nd->mnt = newmnt;

  		nd->dentry = dget(newmnt->mnt_root);
  		schedule_delayed_work(&afs_mntpt_expiry_timer,
  				      afs_mntpt_expiry_timeout * HZ);
  		break;
  	case -EBUSY:
  		/* someone else made a mount here whilst we were busy */
  		while (d_mountpoint(nd->dentry) &&
  		       follow_down(&nd->mnt, &nd->dentry))
  			;
  		err = 0;
  	default:
  		mntput(newmnt);
  		break;

  	}

  	_leave(" = %d", err);

  	return ERR_PTR(err);

  }

  /*
   * handle mountpoint expiry timer going off
   */

  static void afs_mntpt_expiry_timed_out(struct work_struct *work)

  {

  	_enter("");
  
  	if (!list_empty(&afs_vfsmounts)) {
  		mark_mounts_for_expiry(&afs_vfsmounts);
  		schedule_delayed_work(&afs_mntpt_expiry_timer,
  				      afs_mntpt_expiry_timeout * HZ);
  	}
  
  	_leave("");
  }

  /*
   * kill the AFS mountpoint timer if it's still running
   */
  void afs_mntpt_kill_timer(void)
  {
  	_enter("");

  	ASSERT(list_empty(&afs_vfsmounts));
  	cancel_delayed_work(&afs_mntpt_expiry_timer);
  	flush_scheduled_work();
  }

  /*
   * begin unmount by attempting to remove all automounted mountpoints we added
   */
  void afs_umount_begin(struct vfsmount *vfsmnt, int flags)
  {
  	shrink_submounts(vfsmnt, &afs_vfsmounts);

  }