/*
   * fs/kernfs/inode.c - kernfs inode implementation
   *
   * Copyright (c) 2001-3 Patrick Mochel
   * Copyright (c) 2007 SUSE Linux Products GmbH
   * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
   *
   * This file is released under the GPLv2.
   */

  
  #include <linux/pagemap.h>
  #include <linux/backing-dev.h>
  #include <linux/capability.h>
  #include <linux/errno.h>
  #include <linux/slab.h>
  #include <linux/xattr.h>
  #include <linux/security.h>
  
  #include "kernfs-internal.h"

  static const struct address_space_operations kernfs_aops = {

  	.readpage	= simple_readpage,
  	.write_begin	= simple_write_begin,
  	.write_end	= simple_write_end,
  };

  static const struct inode_operations kernfs_iops = {

  	.permission	= kernfs_iop_permission,
  	.setattr	= kernfs_iop_setattr,
  	.getattr	= kernfs_iop_getattr,

  	.listxattr	= kernfs_iop_listxattr,

  };

  static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)

  {

  	static DEFINE_MUTEX(iattr_mutex);
  	struct kernfs_iattrs *ret;

  	struct iattr *iattrs;

  	mutex_lock(&iattr_mutex);

  	if (kn->iattr)

  		goto out_unlock;

  	kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);

  	if (!kn->iattr)

  		goto out_unlock;

  	iattrs = &kn->iattr->ia_iattr;

  
  	/* assign default attributes */

  	iattrs->ia_mode = kn->mode;

  	iattrs->ia_uid = GLOBAL_ROOT_UID;
  	iattrs->ia_gid = GLOBAL_ROOT_GID;

  
  	ktime_get_real_ts(&iattrs->ia_atime);
  	iattrs->ia_mtime = iattrs->ia_atime;
  	iattrs->ia_ctime = iattrs->ia_atime;

  	simple_xattrs_init(&kn->iattr->xattrs);

  out_unlock:
  	ret = kn->iattr;
  	mutex_unlock(&iattr_mutex);
  	return ret;

  }

  static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)

  {

  	struct kernfs_iattrs *attrs;

  	struct iattr *iattrs;
  	unsigned int ia_valid = iattr->ia_valid;

  	attrs = kernfs_iattrs(kn);

  	if (!attrs)
  		return -ENOMEM;

  	iattrs = &attrs->ia_iattr;

  
  	if (ia_valid & ATTR_UID)
  		iattrs->ia_uid = iattr->ia_uid;
  	if (ia_valid & ATTR_GID)
  		iattrs->ia_gid = iattr->ia_gid;
  	if (ia_valid & ATTR_ATIME)
  		iattrs->ia_atime = iattr->ia_atime;
  	if (ia_valid & ATTR_MTIME)
  		iattrs->ia_mtime = iattr->ia_mtime;
  	if (ia_valid & ATTR_CTIME)
  		iattrs->ia_ctime = iattr->ia_ctime;
  	if (ia_valid & ATTR_MODE) {
  		umode_t mode = iattr->ia_mode;

  		iattrs->ia_mode = kn->mode = mode;

  	}
  	return 0;
  }
  
  /**
   * kernfs_setattr - set iattr on a node

   * @kn: target node

   * @iattr: iattr to set
   *
   * Returns 0 on success, -errno on failure.
   */

  int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)

  {
  	int ret;

  	mutex_lock(&kernfs_mutex);

  	ret = __kernfs_setattr(kn, iattr);

  	mutex_unlock(&kernfs_mutex);

  	return ret;
  }

  int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)

  {

  	struct inode *inode = d_inode(dentry);

  	struct kernfs_node *kn = inode->i_private;

  	int error;

  	if (!kn)

  		return -EINVAL;

  	mutex_lock(&kernfs_mutex);

  	error = setattr_prepare(dentry, iattr);

  	if (error)
  		goto out;

  	error = __kernfs_setattr(kn, iattr);

  	if (error)
  		goto out;
  
  	/* this ignores size changes */
  	setattr_copy(inode, iattr);
  
  out:

  	mutex_unlock(&kernfs_mutex);

  	return error;
  }

  static int kernfs_node_setsecdata(struct kernfs_iattrs *attrs, void **secdata,

  				  u32 *secdata_len)

  {

  	void *old_secdata;
  	size_t old_secdata_len;

  	old_secdata = attrs->ia_secdata;
  	old_secdata_len = attrs->ia_secdata_len;

  	attrs->ia_secdata = *secdata;
  	attrs->ia_secdata_len = *secdata_len;

  
  	*secdata = old_secdata;
  	*secdata_len = old_secdata_len;
  	return 0;
  }

  ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)

  {

  	struct kernfs_node *kn = kernfs_dentry_node(dentry);

  	struct kernfs_iattrs *attrs;

  	attrs = kernfs_iattrs(kn);

  	if (!attrs)
  		return -ENOMEM;

  	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);

  }
  
  static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
  {
  	inode->i_mode = mode;

  	inode->i_atime = inode->i_mtime =

  		inode->i_ctime = current_time(inode);

  }
  
  static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
  {

  	struct super_block *sb = inode->i_sb;

  	inode->i_uid = iattr->ia_uid;
  	inode->i_gid = iattr->ia_gid;

  	inode->i_atime = timespec_trunc(iattr->ia_atime, sb->s_time_gran);
  	inode->i_mtime = timespec_trunc(iattr->ia_mtime, sb->s_time_gran);
  	inode->i_ctime = timespec_trunc(iattr->ia_ctime, sb->s_time_gran);

  }

  static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)

  {

  	struct kernfs_iattrs *attrs = kn->iattr;

  	inode->i_mode = kn->mode;

  	if (attrs) {

  		/*
  		 * kernfs_node has non-default attributes get them from
  		 * persistent copy in kernfs_node.

  		 */

  		set_inode_attr(inode, &attrs->ia_iattr);
  		security_inode_notifysecctx(inode, attrs->ia_secdata,
  					    attrs->ia_secdata_len);

  	}

  	if (kernfs_type(kn) == KERNFS_DIR)

  		set_nlink(inode, kn->dir.subdirs + 2);

  }

  int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
  		       u32 request_mask, unsigned int query_flags)

  {

  	struct inode *inode = d_inode(path->dentry);

  	struct kernfs_node *kn = inode->i_private;

  	mutex_lock(&kernfs_mutex);

  	kernfs_refresh_inode(kn, inode);

  	mutex_unlock(&kernfs_mutex);

  
  	generic_fillattr(inode, stat);
  	return 0;
  }

  static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)

  {

  	kernfs_get(kn);
  	inode->i_private = kn;

  	inode->i_mapping->a_ops = &kernfs_aops;

  	inode->i_op = &kernfs_iops;

  	inode->i_generation = kn->id.generation;

  	set_default_inode_attr(inode, kn->mode);

  	kernfs_refresh_inode(kn, inode);

  
  	/* initialize inode according to type */

  	switch (kernfs_type(kn)) {
  	case KERNFS_DIR:

  		inode->i_op = &kernfs_dir_iops;
  		inode->i_fop = &kernfs_dir_fops;

  		if (kn->flags & KERNFS_EMPTY_DIR)
  			make_empty_dir_inode(inode);

  		break;

  	case KERNFS_FILE:

  		inode->i_size = kn->attr.size;

  		inode->i_fop = &kernfs_file_fops;

  		break;

  	case KERNFS_LINK:

  		inode->i_op = &kernfs_symlink_iops;

  		break;
  	default:
  		BUG();
  	}
  
  	unlock_new_inode(inode);
  }
  
  /**

   *	kernfs_get_inode - get inode for kernfs_node

   *	@sb: super block

   *	@kn: kernfs_node to allocate inode for

   *

   *	Get inode for @kn.  If such inode doesn't exist, a new inode is
   *	allocated and basics are initialized.  New inode is returned
   *	locked.

   *
   *	LOCKING:
   *	Kernel thread context (may sleep).
   *
   *	RETURNS:
   *	Pointer to allocated inode on success, NULL on failure.
   */

  struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)

  {
  	struct inode *inode;

  	inode = iget_locked(sb, kn->id.ino);

  	if (inode && (inode->i_state & I_NEW))

  		kernfs_init_inode(kn, inode);

  
  	return inode;
  }
  
  /*

   * The kernfs_node serves as both an inode and a directory entry for
   * kernfs.  To prevent the kernfs inode numbers from being freed
   * prematurely we take a reference to kernfs_node from the kernfs inode.  A

   * super_operations.evict_inode() implementation is needed to drop that
   * reference upon inode destruction.
   */

  void kernfs_evict_inode(struct inode *inode)

  {

  	struct kernfs_node *kn = inode->i_private;

  	truncate_inode_pages_final(&inode->i_data);

  	clear_inode(inode);

  	kernfs_put(kn);

  }

  int kernfs_iop_permission(struct inode *inode, int mask)

  {

  	struct kernfs_node *kn;

  
  	if (mask & MAY_NOT_BLOCK)
  		return -ECHILD;

  	kn = inode->i_private;

  	mutex_lock(&kernfs_mutex);

  	kernfs_refresh_inode(kn, inode);

  	mutex_unlock(&kernfs_mutex);

  
  	return generic_permission(inode, mask);
  }

  
  static int kernfs_xattr_get(const struct xattr_handler *handler,
  			    struct dentry *unused, struct inode *inode,
  			    const char *suffix, void *value, size_t size)
  {
  	const char *name = xattr_full_name(handler, suffix);
  	struct kernfs_node *kn = inode->i_private;
  	struct kernfs_iattrs *attrs;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	return simple_xattr_get(&attrs->xattrs, name, value, size);
  }
  
  static int kernfs_xattr_set(const struct xattr_handler *handler,
  			    struct dentry *unused, struct inode *inode,
  			    const char *suffix, const void *value,
  			    size_t size, int flags)
  {
  	const char *name = xattr_full_name(handler, suffix);
  	struct kernfs_node *kn = inode->i_private;
  	struct kernfs_iattrs *attrs;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
  }

  static const struct xattr_handler kernfs_trusted_xattr_handler = {

  	.prefix = XATTR_TRUSTED_PREFIX,
  	.get = kernfs_xattr_get,
  	.set = kernfs_xattr_set,
  };
  
  static int kernfs_security_xattr_set(const struct xattr_handler *handler,
  				     struct dentry *unused, struct inode *inode,
  				     const char *suffix, const void *value,
  				     size_t size, int flags)
  {
  	struct kernfs_node *kn = inode->i_private;
  	struct kernfs_iattrs *attrs;
  	void *secdata;
  	u32 secdata_len = 0;
  	int error;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	error = security_inode_setsecurity(inode, suffix, value, size, flags);
  	if (error)
  		return error;
  	error = security_inode_getsecctx(inode, &secdata, &secdata_len);
  	if (error)
  		return error;
  
  	mutex_lock(&kernfs_mutex);
  	error = kernfs_node_setsecdata(attrs, &secdata, &secdata_len);
  	mutex_unlock(&kernfs_mutex);
  
  	if (secdata)
  		security_release_secctx(secdata, secdata_len);
  	return error;
  }

  static const struct xattr_handler kernfs_security_xattr_handler = {

  	.prefix = XATTR_SECURITY_PREFIX,
  	.get = kernfs_xattr_get,
  	.set = kernfs_security_xattr_set,
  };
  
  const struct xattr_handler *kernfs_xattr_handlers[] = {
  	&kernfs_trusted_xattr_handler,
  	&kernfs_security_xattr_handler,
  	NULL
  };