/* 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/fs.h>
  #include <linux/pagemap.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/gfp.h>
  #include "internal.h"
  
  
  static struct dentry *afs_mntpt_lookup(struct inode *dir,
  				       struct dentry *dentry,
  				       unsigned int flags);
  static int afs_mntpt_open(struct inode *inode, struct file *file);
  static void afs_mntpt_expiry_timed_out(struct work_struct *work);
  
  const struct file_operations afs_mntpt_file_operations = {
  	.open		= afs_mntpt_open,
  	.llseek		= noop_llseek,
  };
  
  const struct inode_operations afs_mntpt_inode_operations = {
  	.lookup		= afs_mntpt_lookup,
  	.readlink	= page_readlink,
  	.getattr	= afs_getattr,
  };
  
  const struct inode_operations afs_autocell_inode_operations = {
  	.getattr	= afs_getattr,
  };
  
  static LIST_HEAD(afs_vfsmounts);
  static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
  
  static 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 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_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
  			       afs_page_filler, key);
  	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);
  		vnode->vfs_inode.i_flags |= S_AUTOMOUNT;
  		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,
  				       unsigned int flags)
  {
  	_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 afs_vnode *vnode;
  	struct page *page;
  	char *devname, *options;
  	bool rwpath = false;
  	int ret;
  
  	_enter("{%s}", mntpt->d_name.name);
  
  	BUG_ON(!mntpt->d_inode);
  
  	ret = -ENOMEM;
  	devname = (char *) get_zeroed_page(GFP_KERNEL);
  	if (!devname)
  		goto error_no_devname;
  
  	options = (char *) get_zeroed_page(GFP_KERNEL);
  	if (!options)
  		goto error_no_options;
  
  	vnode = AFS_FS_I(mntpt->d_inode);
  	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
  		/* if the directory is a pseudo directory, use the d_name */
  		static const char afs_root_cell[] = ":root.cell.";
  		unsigned size = mntpt->d_name.len;
  
  		ret = -ENOENT;
  		if (size < 2 || size > AFS_MAXCELLNAME)
  			goto error_no_page;
  
  		if (mntpt->d_name.name[0] == '.') {
  			devname[0] = '#';
  			memcpy(devname + 1, mntpt->d_name.name, size - 1);
  			memcpy(devname + size, afs_root_cell,
  			       sizeof(afs_root_cell));
  			rwpath = true;
  		} else {
  			devname[0] = '%';
  			memcpy(devname + 1, mntpt->d_name.name, size);
  			memcpy(devname + size + 1, afs_root_cell,
  			       sizeof(afs_root_cell));
  		}
  	} else {
  		/* read the contents of the AFS special symlink */
  		loff_t size = i_size_read(mntpt->d_inode);
  		char *buf;
  
  		ret = -EINVAL;
  		if (size > PAGE_SIZE - 1)
  			goto error_no_page;
  
  		page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
  		if (IS_ERR(page)) {
  			ret = PTR_ERR(page);
  			goto error_no_page;
  		}
  
  		ret = -EIO;
  		if (PageError(page))
  			goto error;
  
  		buf = kmap_atomic(page);
  		memcpy(devname, buf, size);
  		kunmap_atomic(buf);
  		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 || rwpath)
  		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:
  	page_cache_release(page);
  error_no_page:
  	free_page((unsigned long) options);
  error_no_options:
  	free_page((unsigned long) devname);
  error_no_devname:
  	_leave(" = %d", ret);
  	return ERR_PTR(ret);
  }
  
  /*
   * handle an automount point
   */
  struct vfsmount *afs_d_automount(struct path *path)
  {
  	struct vfsmount *newmnt;
  
  	_enter("{%s}", path->dentry->d_name.name);
  
  	newmnt = afs_mntpt_do_automount(path->dentry);
  	if (IS_ERR(newmnt))
  		return newmnt;
  
  	mntget(newmnt); /* prevent immediate expiration */
  	mnt_set_expiry(newmnt, &afs_vfsmounts);
  	queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
  			   afs_mntpt_expiry_timeout * HZ);
  	_leave(" = %p", newmnt);
  	return newmnt;
  }
  
  /*
   * 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);
  		queue_delayed_work(afs_wq, &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_sync(&afs_mntpt_expiry_timer);
  }