/*
   * Copyright (C) 2007 Red Hat.  All rights reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License v2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */
  
  #include <linux/init.h>
  #include <linux/fs.h>
  #include <linux/slab.h>
  #include <linux/rwsem.h>
  #include <linux/xattr.h>
  #include <linux/security.h>
  #include <linux/posix_acl_xattr.h>
  #include "ctree.h"
  #include "btrfs_inode.h"
  #include "transaction.h"
  #include "xattr.h"
  #include "disk-io.h"
  #include "props.h"
  
  
  ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
  				void *buffer, size_t size)
  {
  	struct btrfs_dir_item *di;
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct btrfs_path *path;
  	struct extent_buffer *leaf;
  	int ret = 0;
  	unsigned long data_ptr;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	/* lookup the xattr by name */
  	di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
  				strlen(name), 0);
  	if (!di) {
  		ret = -ENODATA;
  		goto out;
  	} else if (IS_ERR(di)) {
  		ret = PTR_ERR(di);
  		goto out;
  	}
  
  	leaf = path->nodes[0];
  	/* if size is 0, that means we want the size of the attr */
  	if (!size) {
  		ret = btrfs_dir_data_len(leaf, di);
  		goto out;
  	}
  
  	/* now get the data out of our dir_item */
  	if (btrfs_dir_data_len(leaf, di) > size) {
  		ret = -ERANGE;
  		goto out;
  	}
  
  	/*
  	 * The way things are packed into the leaf is like this
  	 * |struct btrfs_dir_item|name|data|
  	 * where name is the xattr name, so security.foo, and data is the
  	 * content of the xattr.  data_ptr points to the location in memory
  	 * where the data starts in the in memory leaf
  	 */
  	data_ptr = (unsigned long)((char *)(di + 1) +
  				   btrfs_dir_name_len(leaf, di));
  	read_extent_buffer(leaf, buffer, data_ptr,
  			   btrfs_dir_data_len(leaf, di));
  	ret = btrfs_dir_data_len(leaf, di);
  
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  static int do_setxattr(struct btrfs_trans_handle *trans,
  		       struct inode *inode, const char *name,
  		       const void *value, size_t size, int flags)
  {
  	struct btrfs_dir_item *di;
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct btrfs_path *path;
  	size_t name_len = strlen(name);
  	int ret = 0;
  
  	if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
  		return -ENOSPC;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	if (flags & XATTR_REPLACE) {
  		di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
  					name_len, -1);
  		if (IS_ERR(di)) {
  			ret = PTR_ERR(di);
  			goto out;
  		} else if (!di) {
  			ret = -ENODATA;
  			goto out;
  		}
  		ret = btrfs_delete_one_dir_name(trans, root, path, di);
  		if (ret)
  			goto out;
  		btrfs_release_path(path);
  
  		/*
  		 * remove the attribute
  		 */
  		if (!value)
  			goto out;
  	} else {
  		di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
  					name, name_len, 0);
  		if (IS_ERR(di)) {
  			ret = PTR_ERR(di);
  			goto out;
  		}
  		if (!di && !value)
  			goto out;
  		btrfs_release_path(path);
  	}
  
  again:
  	ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
  				      name, name_len, value, size);
  	/*
  	 * If we're setting an xattr to a new value but the new value is say
  	 * exactly BTRFS_MAX_XATTR_SIZE, we could end up with EOVERFLOW getting
  	 * back from split_leaf.  This is because it thinks we'll be extending
  	 * the existing item size, but we're asking for enough space to add the
  	 * item itself.  So if we get EOVERFLOW just set ret to EEXIST and let
  	 * the rest of the function figure it out.
  	 */
  	if (ret == -EOVERFLOW)
  		ret = -EEXIST;
  
  	if (ret == -EEXIST) {
  		if (flags & XATTR_CREATE)
  			goto out;
  		/*
  		 * We can't use the path we already have since we won't have the
  		 * proper locking for a delete, so release the path and
  		 * re-lookup to delete the thing.
  		 */
  		btrfs_release_path(path);
  		di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
  					name, name_len, -1);
  		if (IS_ERR(di)) {
  			ret = PTR_ERR(di);
  			goto out;
  		} else if (!di) {
  			/* Shouldn't happen but just in case... */
  			btrfs_release_path(path);
  			goto again;
  		}
  
  		ret = btrfs_delete_one_dir_name(trans, root, path, di);
  		if (ret)
  			goto out;
  
  		/*
  		 * We have a value to set, so go back and try to insert it now.
  		 */
  		if (value) {
  			btrfs_release_path(path);
  			goto again;
  		}
  	}
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  /*
   * @value: "" makes the attribute to empty, NULL removes it
   */
  int __btrfs_setxattr(struct btrfs_trans_handle *trans,
  		     struct inode *inode, const char *name,
  		     const void *value, size_t size, int flags)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	int ret;
  
  	if (trans)
  		return do_setxattr(trans, inode, name, value, size, flags);
  
  	trans = btrfs_start_transaction(root, 2);
  	if (IS_ERR(trans))
  		return PTR_ERR(trans);
  
  	ret = do_setxattr(trans, inode, name, value, size, flags);
  	if (ret)
  		goto out;
  
  	inode_inc_iversion(inode);
  	inode->i_ctime = CURRENT_TIME;
  	set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
  	ret = btrfs_update_inode(trans, root, inode);
  	BUG_ON(ret);
  out:
  	btrfs_end_transaction(trans, root);
  	return ret;
  }
  
  ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
  {
  	struct btrfs_key key, found_key;
  	struct inode *inode = dentry->d_inode;
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct btrfs_path *path;
  	struct extent_buffer *leaf;
  	struct btrfs_dir_item *di;
  	int ret = 0, slot;
  	size_t total_size = 0, size_left = size;
  	unsigned long name_ptr;
  	size_t name_len;
  
  	/*
  	 * ok we want all objects associated with this id.
  	 * NOTE: we set key.offset = 0; because we want to start with the
  	 * first xattr that we find and walk forward
  	 */
  	key.objectid = btrfs_ino(inode);
  	btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
  	key.offset = 0;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  	path->reada = 2;
  
  	/* search for our xattrs */
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0)
  		goto err;
  
  	while (1) {
  		leaf = path->nodes[0];
  		slot = path->slots[0];
  
  		/* this is where we start walking through the path */
  		if (slot >= btrfs_header_nritems(leaf)) {
  			/*
  			 * if we've reached the last slot in this leaf we need
  			 * to go to the next leaf and reset everything
  			 */
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				goto err;
  			else if (ret > 0)
  				break;
  			continue;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &found_key, slot);
  
  		/* check to make sure this item is what we want */
  		if (found_key.objectid != key.objectid)
  			break;
  		if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
  			break;
  
  		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
  		if (verify_dir_item(root, leaf, di))
  			goto next;
  
  		name_len = btrfs_dir_name_len(leaf, di);
  		total_size += name_len + 1;
  
  		/* we are just looking for how big our buffer needs to be */
  		if (!size)
  			goto next;
  
  		if (!buffer || (name_len + 1) > size_left) {
  			ret = -ERANGE;
  			goto err;
  		}
  
  		name_ptr = (unsigned long)(di + 1);
  		read_extent_buffer(leaf, buffer, name_ptr, name_len);
  		buffer[name_len] = '\0';
  
  		size_left -= name_len + 1;
  		buffer += name_len + 1;
  next:
  		path->slots[0]++;
  	}
  	ret = total_size;
  
  err:
  	btrfs_free_path(path);
  
  	return ret;
  }
  
  /*
   * List of handlers for synthetic system.* attributes.  All real ondisk
   * attributes are handled directly.
   */
  const struct xattr_handler *btrfs_xattr_handlers[] = {
  #ifdef CONFIG_BTRFS_FS_POSIX_ACL
  	&posix_acl_access_xattr_handler,
  	&posix_acl_default_xattr_handler,
  #endif
  	NULL,
  };
  
  /*
   * Check if the attribute is in a supported namespace.
   *
   * This applied after the check for the synthetic attributes in the system
   * namespace.
   */
  static bool btrfs_is_valid_xattr(const char *name)
  {
  	return !strncmp(name, XATTR_SECURITY_PREFIX,
  			XATTR_SECURITY_PREFIX_LEN) ||
  	       !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
  	       !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
  	       !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) ||
  		!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN);
  }
  
  ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
  		       void *buffer, size_t size)
  {
  	/*
  	 * If this is a request for a synthetic attribute in the system.*
  	 * namespace use the generic infrastructure to resolve a handler
  	 * for it via sb->s_xattr.
  	 */
  	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  		return generic_getxattr(dentry, name, buffer, size);
  
  	if (!btrfs_is_valid_xattr(name))
  		return -EOPNOTSUPP;
  	return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
  }
  
  int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
  		   size_t size, int flags)
  {
  	struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
  
  	/*
  	 * The permission on security.* and system.* is not checked
  	 * in permission().
  	 */
  	if (btrfs_root_readonly(root))
  		return -EROFS;
  
  	/*
  	 * If this is a request for a synthetic attribute in the system.*
  	 * namespace use the generic infrastructure to resolve a handler
  	 * for it via sb->s_xattr.
  	 */
  	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  		return generic_setxattr(dentry, name, value, size, flags);
  
  	if (!btrfs_is_valid_xattr(name))
  		return -EOPNOTSUPP;
  
  	if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
  		return btrfs_set_prop(dentry->d_inode, name,
  				      value, size, flags);
  
  	if (size == 0)
  		value = "";  /* empty EA, do not remove */
  
  	return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
  				flags);
  }
  
  int btrfs_removexattr(struct dentry *dentry, const char *name)
  {
  	struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
  
  	/*
  	 * The permission on security.* and system.* is not checked
  	 * in permission().
  	 */
  	if (btrfs_root_readonly(root))
  		return -EROFS;
  
  	/*
  	 * If this is a request for a synthetic attribute in the system.*
  	 * namespace use the generic infrastructure to resolve a handler
  	 * for it via sb->s_xattr.
  	 */
  	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  		return generic_removexattr(dentry, name);
  
  	if (!btrfs_is_valid_xattr(name))
  		return -EOPNOTSUPP;
  
  	if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
  		return btrfs_set_prop(dentry->d_inode, name,
  				      NULL, 0, XATTR_REPLACE);
  
  	return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
  				XATTR_REPLACE);
  }
  
  static int btrfs_initxattrs(struct inode *inode,
  			    const struct xattr *xattr_array, void *fs_info)
  {
  	const struct xattr *xattr;
  	struct btrfs_trans_handle *trans = fs_info;
  	char *name;
  	int err = 0;
  
  	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
  		name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
  			       strlen(xattr->name) + 1, GFP_NOFS);
  		if (!name) {
  			err = -ENOMEM;
  			break;
  		}
  		strcpy(name, XATTR_SECURITY_PREFIX);
  		strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
  		err = __btrfs_setxattr(trans, inode, name,
  				       xattr->value, xattr->value_len, 0);
  		kfree(name);
  		if (err < 0)
  			break;
  	}
  	return err;
  }
  
  int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
  			      struct inode *inode, struct inode *dir,
  			      const struct qstr *qstr)
  {
  	return security_inode_init_security(inode, dir, qstr,
  					    &btrfs_initxattrs, trans);
  }