/*

   * fs/sysfs/inode.c - basic sysfs inode and dentry operations

   *

   * Copyright (c) 2001-3 Patrick Mochel
   * Copyright (c) 2007 SUSE Linux Products GmbH
   * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   *
   * This file is released under the GPLv2.

   *
   * Please see Documentation/filesystems/sysfs.txt for more information.
   */
  
  #undef DEBUG 
  
  #include <linux/pagemap.h>
  #include <linux/namei.h>
  #include <linux/backing-dev.h>

  #include <linux/capability.h>

  #include <linux/errno.h>

  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/sysfs.h>

  #include <linux/xattr.h>
  #include <linux/security.h>

  #include "sysfs.h"
  
  extern struct super_block * sysfs_sb;

  static const struct address_space_operations sysfs_aops = {

  	.readpage	= simple_readpage,

  	.write_begin	= simple_write_begin,
  	.write_end	= simple_write_end,

  };
  
  static struct backing_dev_info sysfs_backing_dev_info = {

  	.name		= "sysfs",

  	.ra_pages	= 0,	/* No readahead */

  	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,

  };

  static const struct inode_operations sysfs_inode_operations ={

  	.permission	= sysfs_permission,

  	.setattr	= sysfs_setattr,

  	.getattr	= sysfs_getattr,

  	.setxattr	= sysfs_setxattr,

  };

  int __init sysfs_inode_init(void)
  {
  	return bdi_init(&sysfs_backing_dev_info);
  }

  static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)

  {
  	struct sysfs_inode_attrs *attrs;
  	struct iattr *iattrs;
  
  	attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
  	if (!attrs)
  		return NULL;
  	iattrs = &attrs->ia_iattr;
  
  	/* assign default attributes */
  	iattrs->ia_mode = sd->s_mode;
  	iattrs->ia_uid = 0;
  	iattrs->ia_gid = 0;
  	iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  
  	return attrs;
  }

  int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr * iattr)

  {

  	struct sysfs_inode_attrs *sd_attrs;
  	struct iattr *iattrs;

  	unsigned int ia_valid = iattr->ia_valid;

  	sd_attrs = sd->s_iattr;

  	if (!sd_attrs) {

  		/* setting attributes for the first time, allocate now */

  		sd_attrs = sysfs_init_inode_attrs(sd);
  		if (!sd_attrs)

  			return -ENOMEM;

  		sd->s_iattr = sd_attrs;

  	}
  	/* attributes were changed at least once in past */
  	iattrs = &sd_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 = sd->s_mode = mode;

  	}

  	return 0;
  }
  
  int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
  {
  	struct inode *inode = dentry->d_inode;
  	struct sysfs_dirent *sd = dentry->d_fsdata;
  	int error;
  
  	if (!sd)
  		return -EINVAL;

  	mutex_lock(&sysfs_mutex);

  	error = inode_change_ok(inode, iattr);
  	if (error)

  		goto out;

  	error = sysfs_sd_setattr(sd, iattr);
  	if (error)
  		goto out;

  	/* this ignores size changes */

  	setattr_copy(inode, iattr);

  out:

  	mutex_unlock(&sysfs_mutex);

  	return error;
  }

  static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata, u32 *secdata_len)
  {
  	struct sysfs_inode_attrs *iattrs;
  	void *old_secdata;
  	size_t old_secdata_len;
  
  	iattrs = sd->s_iattr;
  	if (!iattrs)
  		iattrs = sysfs_init_inode_attrs(sd);
  	if (!iattrs)
  		return -ENOMEM;
  
  	old_secdata = iattrs->ia_secdata;
  	old_secdata_len = iattrs->ia_secdata_len;
  
  	iattrs->ia_secdata = *secdata;
  	iattrs->ia_secdata_len = *secdata_len;
  
  	*secdata = old_secdata;
  	*secdata_len = old_secdata_len;
  	return 0;
  }

  int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
  		size_t size, int flags)
  {
  	struct sysfs_dirent *sd = dentry->d_fsdata;

  	void *secdata;
  	int error;
  	u32 secdata_len = 0;
  
  	if (!sd)
  		return -EINVAL;

  
  	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
  		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
  		error = security_inode_setsecurity(dentry->d_inode, suffix,
  						value, size, flags);
  		if (error)
  			goto out;
  		error = security_inode_getsecctx(dentry->d_inode,
  						&secdata, &secdata_len);
  		if (error)
  			goto out;

  		mutex_lock(&sysfs_mutex);
  		error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
  		mutex_unlock(&sysfs_mutex);
  
  		if (secdata)
  			security_release_secctx(secdata, secdata_len);

  	} else
  		return -EINVAL;
  out:

  	return error;
  }

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

  	inode->i_uid = iattr->ia_uid;
  	inode->i_gid = iattr->ia_gid;
  	inode->i_atime = iattr->ia_atime;
  	inode->i_mtime = iattr->ia_mtime;
  	inode->i_ctime = iattr->ia_ctime;
  }

  static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
  {
  	struct sysfs_inode_attrs *iattrs = sd->s_iattr;
  
  	inode->i_mode = sd->s_mode;
  	if (iattrs) {
  		/* sysfs_dirent has non-default attributes
  		 * get them from persistent copy in sysfs_dirent
  		 */
  		set_inode_attr(inode, &iattrs->ia_iattr);
  		security_inode_notifysecctx(inode,
  					    iattrs->ia_secdata,
  					    iattrs->ia_secdata_len);
  	}
  
  	if (sysfs_type(sd) == SYSFS_DIR)

  		set_nlink(inode, sd->s_dir.subdirs + 2);

  }
  
  int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
  {
  	struct sysfs_dirent *sd = dentry->d_fsdata;
  	struct inode *inode = dentry->d_inode;
  
  	mutex_lock(&sysfs_mutex);
  	sysfs_refresh_inode(sd, inode);
  	mutex_unlock(&sysfs_mutex);
  
  	generic_fillattr(inode, stat);
  	return 0;
  }

  static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)

  {

  	struct bin_attribute *bin_attr;

  	inode->i_private = sysfs_get(sd);

  	inode->i_mapping->a_ops = &sysfs_aops;
  	inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
  	inode->i_op = &sysfs_inode_operations;

  	set_default_inode_attr(inode, sd->s_mode);
  	sysfs_refresh_inode(sd, inode);

  	/* initialize inode according to type */
  	switch (sysfs_type(sd)) {

  	case SYSFS_DIR:
  		inode->i_op = &sysfs_dir_inode_operations;
  		inode->i_fop = &sysfs_dir_operations;

  		break;
  	case SYSFS_KOBJ_ATTR:
  		inode->i_size = PAGE_SIZE;
  		inode->i_fop = &sysfs_file_operations;
  		break;
  	case SYSFS_KOBJ_BIN_ATTR:

  		bin_attr = sd->s_bin_attr.bin_attr;

  		inode->i_size = bin_attr->size;
  		inode->i_fop = &bin_fops;
  		break;
  	case SYSFS_KOBJ_LINK:
  		inode->i_op = &sysfs_symlink_inode_operations;
  		break;
  	default:
  		BUG();
  	}
  
  	unlock_new_inode(inode);

  }
  
  /**

   *	sysfs_get_inode - get inode for sysfs_dirent

   *	@sb: super block

   *	@sd: sysfs_dirent to allocate inode for
   *

   *	Get inode for @sd.  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 * sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd)

  {
  	struct inode *inode;

  	inode = iget_locked(sb, sd->s_ino);

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

  		sysfs_init_inode(sd, inode);

  	return inode;
  }

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

   * super_operations.evict_inode() implementation is needed to drop that

   * reference upon inode destruction.
   */

  void sysfs_evict_inode(struct inode *inode)

  {
  	struct sysfs_dirent *sd  = inode->i_private;
  
  	truncate_inode_pages(&inode->i_data, 0);

  	end_writeback(inode);

  	sysfs_put(sd);
  }

  int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const char *name)

  {

  	struct sysfs_addrm_cxt acxt;

  	struct sysfs_dirent *sd;

  	if (!dir_sd)

  		return -ENOENT;

  	sysfs_addrm_start(&acxt, dir_sd);

  	sd = sysfs_find_dirent(dir_sd, ns, name);

  	if (sd)
  		sysfs_remove_one(&acxt, sd);

  	sysfs_addrm_finish(&acxt);
  
  	if (sd)

  		return 0;

  	else
  		return -ENOENT;

  }

  int sysfs_permission(struct inode *inode, int mask)

  {

  	struct sysfs_dirent *sd;

  	if (mask & MAY_NOT_BLOCK)

  		return -ECHILD;
  
  	sd = inode->i_private;

  
  	mutex_lock(&sysfs_mutex);
  	sysfs_refresh_inode(sd, inode);
  	mutex_unlock(&sysfs_mutex);

  	return generic_permission(inode, mask);

  }