// SPDX-License-Identifier: GPL-2.0-or-later

  /* mountpoint management

   *
   * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)

   */
  
  #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 <linux/fs_context.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,

  	.listxattr	= afs_listxattr,

  };

  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;

  static const char afs_root_volume[] = "root.cell";

  /*

   * 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{%pd2}", dir, dentry, dentry);

  	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{%pD2}", inode, file, file);

  	return -EREMOTE;

  }

  /*

   * Set the parameters for the proposed superblock.

   */

  static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)

  {

  	struct afs_fs_context *ctx = fc->fs_private;
  	struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
  	struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
  	struct afs_cell *cell;
  	const char *p;

  	int ret;

  	if (fc->net_ns != src_as->net_ns) {
  		put_net(fc->net_ns);
  		fc->net_ns = get_net(src_as->net_ns);
  	}

  	if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
  		ctx->type = AFSVL_RWVOL;
  		ctx->force = true;
  	}
  	if (ctx->cell) {
  		afs_put_cell(ctx->net, ctx->cell);
  		ctx->cell = NULL;
  	}

  	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
  		/* if the directory is a pseudo directory, use the d_name */

  		unsigned size = mntpt->d_name.len;

  		if (size < 2)
  			return -ENOENT;

  		p = mntpt->d_name.name;

  		if (mntpt->d_name.name[0] == '.') {

  			size--;
  			p++;
  			ctx->type = AFSVL_RWVOL;
  			ctx->force = true;

  		}

  		if (size > AFS_MAXCELLNAME)
  			return -ENAMETOOLONG;
  
  		cell = afs_lookup_cell(ctx->net, p, size, NULL, false);
  		if (IS_ERR(cell)) {
  			pr_err("kAFS: unable to lookup cell '%pd'
  ", mntpt);
  			return PTR_ERR(cell);
  		}
  		ctx->cell = cell;
  
  		ctx->volname = afs_root_volume;
  		ctx->volnamesz = sizeof(afs_root_volume) - 1;

  	} else {
  		/* read the contents of the AFS special symlink */

  		struct page *page;

  		loff_t size = i_size_read(d_inode(mntpt));

  		char *buf;

  		if (src_as->cell)
  			ctx->cell = afs_get_cell(src_as->cell);

  		if (size < 2 || size > PAGE_SIZE - 1)

  			return -EINVAL;

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

  		if (IS_ERR(page))
  			return PTR_ERR(page);

  		if (PageError(page)) {
  			ret = afs_bad(AFS_FS_I(d_inode(mntpt)), afs_file_error_mntpt);

  			put_page(page);
  			return ret;

  		}

  		buf = kmap(page);

  		ret = -EINVAL;
  		if (buf[size - 1] == '.')
  			ret = vfs_parse_fs_string(fc, "source", buf, size - 1);

  		kunmap(page);

  		put_page(page);

  		if (ret < 0)
  			return ret;

  	}

  	return 0;
  }

  /*
   * create a vfsmount to be automounted
   */
  static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
  {
  	struct fs_context *fc;
  	struct vfsmount *mnt;
  	int ret;

  	BUG_ON(!d_inode(mntpt));

  	fc = fs_context_for_submount(&afs_fs_type, mntpt);
  	if (IS_ERR(fc))
  		return ERR_CAST(fc);
  
  	ret = afs_mntpt_set_params(fc, mntpt);
  	if (!ret)
  		mnt = fc_mount(fc);
  	else
  		mnt = ERR_PTR(ret);
  
  	put_fs_context(fc);
  	return mnt;

  }

  /*

   * handle an automount point

   */

  struct vfsmount *afs_d_automount(struct path *path)

  {
  	struct vfsmount *newmnt;

  	_enter("{%pd}", path->dentry);

  	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);

  }