fs/btrfs/xattr.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2007 Red Hat.  All rights reserved.
  */

 #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 <linux/iversion.h>
 #include <linux/sched/mm.h>
 #include "ctree.h"
 #include "fs.h"
 #include "messages.h"
 #include "btrfs_inode.h"
 #include "transaction.h"
 #include "xattr.h"
 #include "disk-io.h"
 #include "props.h"
 #include "locking.h"
 #include "accessors.h"
 #include "dir-item.h"

 int 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(BTRFS_I(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;
 }

 int btrfs_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 = NULL;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_path *path;
 	size_t name_len = strlen(name);
 	int ret = 0;

 	ASSERT(trans);

 	if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
 		return -ENOSPC;

 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
 	path->skip_release_on_error = 1;

 	if (!value) {
 		di = btrfs_lookup_xattr(trans, root, path,
 				btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
 		if (!di && (flags & XATTR_REPLACE))
 			ret = -ENODATA;
 		else if (IS_ERR(di))
 			ret = PTR_ERR(di);
 		else if (di)
 			ret = btrfs_delete_one_dir_name(trans, root, path, di);
 		goto out;
 	}

 	/*
 	 * For a replace we can't just do the insert blindly.
 	 * Do a lookup first (read-only btrfs_search_slot), and return if xattr
 	 * doesn't exist. If it exists, fall down below to the insert/replace
 	 * path - we can't race with a concurrent xattr delete, because the VFS
 	 * locks the inode's i_mutex before calling setxattr or removexattr.
 	 */
 	if (flags & XATTR_REPLACE) {
 		ASSERT(inode_is_locked(inode));
 		di = btrfs_lookup_xattr(NULL, root, path,
 				btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
 		if (!di)
 			ret = -ENODATA;
 		else if (IS_ERR(di))
 			ret = PTR_ERR(di);
 		if (ret)
 			goto out;
 		btrfs_release_path(path);
 		di = NULL;
 	}

 	ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
 				      name, name_len, value, size);
 	if (ret == -EOVERFLOW) {
 		/*
 		 * We have an existing item in a leaf, split_leaf couldn't
 		 * expand it. That item might have or not a dir_item that
 		 * matches our target xattr, so lets check.
 		 */
 		ret = 0;
 		btrfs_assert_tree_write_locked(path->nodes[0]);
 		di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 		if (!di && !(flags & XATTR_REPLACE)) {
 			ret = -ENOSPC;
 			goto out;
 		}
 	} else if (ret == -EEXIST) {
 		ret = 0;
 		di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 		ASSERT(di); /* logic error */
 	} else if (ret) {
 		goto out;
 	}

 	if (di && (flags & XATTR_CREATE)) {
 		ret = -EEXIST;
 		goto out;
 	}

 	if (di) {
 		/*
 		 * We're doing a replace, and it must be atomic, that is, at
 		 * any point in time we have either the old or the new xattr
 		 * value in the tree. We don't want readers (getxattr and
 		 * listxattrs) to miss a value, this is specially important
 		 * for ACLs.
 		 */
 		const int slot = path->slots[0];
 		struct extent_buffer *leaf = path->nodes[0];
 		const u16 old_data_len = btrfs_dir_data_len(leaf, di);
 		const u32 item_size = btrfs_item_size(leaf, slot);
 		const u32 data_size = sizeof(*di) + name_len + size;
 		unsigned long data_ptr;
 		char *ptr;

 		if (size > old_data_len) {
 			if (btrfs_leaf_free_space(leaf) <
 			    (size - old_data_len)) {
 				ret = -ENOSPC;
 				goto out;
 			}
 		}

 		if (old_data_len + name_len + sizeof(*di) == item_size) {
 			/* No other xattrs packed in the same leaf item. */
 			if (size > old_data_len)
 				btrfs_extend_item(path, size - old_data_len);
 			else if (size < old_data_len)
 				btrfs_truncate_item(path, data_size, 1);
 		} else {
 			/* There are other xattrs packed in the same item. */
 			ret = btrfs_delete_one_dir_name(trans, root, path, di);
 			if (ret)
 				goto out;
 			btrfs_extend_item(path, data_size);
 		}

 		ptr = btrfs_item_ptr(leaf, slot, char);
 		ptr += btrfs_item_size(leaf, slot) - data_size;
 		di = (struct btrfs_dir_item *)ptr;
 		btrfs_set_dir_data_len(leaf, di, size);
 		data_ptr = ((unsigned long)(di + 1)) + name_len;
 		write_extent_buffer(leaf, value, data_ptr, size);
 		btrfs_mark_buffer_dirty(leaf);
 	} else {
 		/*
 		 * Insert, and we had space for the xattr, so path->slots[0] is
 		 * where our xattr dir_item is and btrfs_insert_xattr_item()
 		 * filled it.
 		 */
 	}
 out:
 	btrfs_free_path(path);
 	if (!ret) {
 		set_bit(BTRFS_INODE_COPY_EVERYTHING,
 			&BTRFS_I(inode)->runtime_flags);
 		clear_bit(BTRFS_INODE_NO_XATTRS, &BTRFS_I(inode)->runtime_flags);
 	}
 	return ret;
 }

 /*
  * @value: "" makes the attribute to empty, NULL removes it
  */
 int btrfs_setxattr_trans(struct inode *inode, const char *name,
 			 const void *value, size_t size, int flags)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_trans_handle *trans;
 	const bool start_trans = (current->journal_info == NULL);
 	int ret;

 	if (start_trans) {
 		/*
 		 * 1 unit for inserting/updating/deleting the xattr
 		 * 1 unit for the inode item update
 		 */
 		trans = btrfs_start_transaction(root, 2);
 		if (IS_ERR(trans))
 			return PTR_ERR(trans);
 	} else {
 		/*
 		 * This can happen when smack is enabled and a directory is being
 		 * created. It happens through d_instantiate_new(), which calls
 		 * smack_d_instantiate(), which in turn calls __vfs_setxattr() to
 		 * set the transmute xattr (XATTR_NAME_SMACKTRANSMUTE) on the
 		 * inode. We have already reserved space for the xattr and inode
 		 * update at btrfs_mkdir(), so just use the transaction handle.
 		 * We don't join or start a transaction, as that will reset the
 		 * block_rsv of the handle and trigger a warning for the start
 		 * case.
 		 */
 		ASSERT(strncmp(name, XATTR_SECURITY_PREFIX,
 			       XATTR_SECURITY_PREFIX_LEN) == 0);
 		trans = current->journal_info;
 	}

 	ret = btrfs_setxattr(trans, inode, name, value, size, flags);
 	if (ret)
 		goto out;

 	inode_inc_iversion(inode);
 	inode->i_ctime = current_time(inode);
 	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
 	if (ret)
 		btrfs_abort_transaction(trans, ret);
 out:
 	if (start_trans)
 		btrfs_end_transaction(trans);
 	return ret;
 }

 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 {
 	struct btrfs_key found_key;
 	struct btrfs_key key;
 	struct inode *inode = d_inode(dentry);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_path *path;
 	int iter_ret = 0;
 	int ret = 0;
 	size_t total_size = 0, size_left = size;

 	/*
 	 * 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(BTRFS_I(inode));
 	key.type = BTRFS_XATTR_ITEM_KEY;
 	key.offset = 0;

 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
 	path->reada = READA_FORWARD;

 	/* search for our xattrs */
 	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 		struct extent_buffer *leaf;
 		int slot;
 		struct btrfs_dir_item *di;
 		u32 item_size;
 		u32 cur;

 		leaf = path->nodes[0];
 		slot = path->slots[0];

 		/* check to make sure this item is what we want */
 		if (found_key.objectid != key.objectid)
 			break;
 		if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 			break;
 		if (found_key.type < BTRFS_XATTR_ITEM_KEY)
 			continue;

 		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 		item_size = btrfs_item_size(leaf, slot);
 		cur = 0;
 		while (cur < item_size) {
 			u16 name_len = btrfs_dir_name_len(leaf, di);
 			u16 data_len = btrfs_dir_data_len(leaf, di);
 			u32 this_len = sizeof(*di) + name_len + data_len;
 			unsigned long name_ptr = (unsigned long)(di + 1);

 			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) {
 			        iter_ret = -ERANGE;
 				break;
 			}

 			read_extent_buffer(leaf, buffer, name_ptr, name_len);
 			buffer[name_len] = '\0';

 			size_left -= name_len + 1;
 			buffer += name_len + 1;
 next:
 			cur += this_len;
 			di = (struct btrfs_dir_item *)((char *)di + this_len);
 		}
 	}

 	if (iter_ret < 0)
 		ret = iter_ret;
 	else
 		ret = total_size;

 	btrfs_free_path(path);

 	return ret;
 }

 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
 				   struct dentry *unused, struct inode *inode,
 				   const char *name, void *buffer, size_t size)
 {
 	name = xattr_full_name(handler, name);
 	return btrfs_getxattr(inode, name, buffer, size);
 }

 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
 				   struct mnt_idmap *idmap,
 				   struct dentry *unused, struct inode *inode,
 				   const char *name, const void *buffer,
 				   size_t size, int flags)
 {
 	if (btrfs_root_readonly(BTRFS_I(inode)->root))
 		return -EROFS;

 	name = xattr_full_name(handler, name);
 	return btrfs_setxattr_trans(inode, name, buffer, size, flags);
 }

 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
 					struct mnt_idmap *idmap,
 					struct dentry *unused, struct inode *inode,
 					const char *name, const void *value,
 					size_t size, int flags)
 {
 	int ret;
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(inode)->root;

 	name = xattr_full_name(handler, name);
 	ret = btrfs_validate_prop(BTRFS_I(inode), name, value, size);
 	if (ret)
 		return ret;

 	if (btrfs_ignore_prop(BTRFS_I(inode), name))
 		return 0;

 	trans = btrfs_start_transaction(root, 2);
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);

 	ret = btrfs_set_prop(trans, inode, name, value, size, flags);
 	if (!ret) {
 		inode_inc_iversion(inode);
 		inode->i_ctime = current_time(inode);
 		ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
 		if (ret)
 			btrfs_abort_transaction(trans, ret);
 	}

 	btrfs_end_transaction(trans);

 	return ret;
 }

 static const struct xattr_handler btrfs_security_xattr_handler = {
 	.prefix = XATTR_SECURITY_PREFIX,
 	.get = btrfs_xattr_handler_get,
 	.set = btrfs_xattr_handler_set,
 };

 static const struct xattr_handler btrfs_trusted_xattr_handler = {
 	.prefix = XATTR_TRUSTED_PREFIX,
 	.get = btrfs_xattr_handler_get,
 	.set = btrfs_xattr_handler_set,
 };

 static const struct xattr_handler btrfs_user_xattr_handler = {
 	.prefix = XATTR_USER_PREFIX,
 	.get = btrfs_xattr_handler_get,
 	.set = btrfs_xattr_handler_set,
 };

 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
 	.prefix = XATTR_BTRFS_PREFIX,
 	.get = btrfs_xattr_handler_get,
 	.set = btrfs_xattr_handler_set_prop,
 };

 const struct xattr_handler *btrfs_xattr_handlers[] = {
 	&btrfs_security_xattr_handler,
 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 	&posix_acl_access_xattr_handler,
 	&posix_acl_default_xattr_handler,
 #endif
 	&btrfs_trusted_xattr_handler,
 	&btrfs_user_xattr_handler,
 	&btrfs_btrfs_xattr_handler,
 	NULL,
 };

 static int btrfs_initxattrs(struct inode *inode,
 			    const struct xattr *xattr_array, void *fs_private)
 {
 	struct btrfs_trans_handle *trans = fs_private;
 	const struct xattr *xattr;
 	unsigned int nofs_flag;
 	char *name;
 	int err = 0;

 	/*
 	 * We're holding a transaction handle, so use a NOFS memory allocation
 	 * context to avoid deadlock if reclaim happens.
 	 */
 	nofs_flag = memalloc_nofs_save();
 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 		name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 			       strlen(xattr->name) + 1, GFP_KERNEL);
 		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;
 	}
 	memalloc_nofs_restore(nofs_flag);
 	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);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2007 Red Hat. All rights reserved.
	*/

	#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 <linux/iversion.h>
	#include <linux/sched/mm.h>
	#include "ctree.h"
	#include "fs.h"
	#include "messages.h"
	#include "btrfs_inode.h"
	#include "transaction.h"
	#include "xattr.h"
	#include "disk-io.h"
	#include "props.h"
	#include "locking.h"
	#include "accessors.h"
	#include "dir-item.h"

	int 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(BTRFS_I(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;
	}

	int btrfs_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 = NULL;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct btrfs_fs_info *fs_info = root->fs_info;
	struct btrfs_path *path;
	size_t name_len = strlen(name);
	int ret = 0;

	ASSERT(trans);

	if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
	return -ENOSPC;

	path = btrfs_alloc_path();
	if (!path)
	return -ENOMEM;
	path->skip_release_on_error = 1;

	if (!value) {
	di = btrfs_lookup_xattr(trans, root, path,
	btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
	if (!di && (flags & XATTR_REPLACE))
	ret = -ENODATA;
	else if (IS_ERR(di))
	ret = PTR_ERR(di);
	else if (di)
	ret = btrfs_delete_one_dir_name(trans, root, path, di);
	goto out;
	}

	/*
	* For a replace we can't just do the insert blindly.
	* Do a lookup first (read-only btrfs_search_slot), and return if xattr
	* doesn't exist. If it exists, fall down below to the insert/replace
	* path - we can't race with a concurrent xattr delete, because the VFS
	* locks the inode's i_mutex before calling setxattr or removexattr.
	*/
	if (flags & XATTR_REPLACE) {
	ASSERT(inode_is_locked(inode));
	di = btrfs_lookup_xattr(NULL, root, path,
	btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
	if (!di)
	ret = -ENODATA;
	else if (IS_ERR(di))
	ret = PTR_ERR(di);
	if (ret)
	goto out;
	btrfs_release_path(path);
	di = NULL;
	}

	ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
	name, name_len, value, size);
	if (ret == -EOVERFLOW) {
	/*
	* We have an existing item in a leaf, split_leaf couldn't
	* expand it. That item might have or not a dir_item that
	* matches our target xattr, so lets check.
	*/
	ret = 0;
	btrfs_assert_tree_write_locked(path->nodes[0]);
	di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
	if (!di && !(flags & XATTR_REPLACE)) {
	ret = -ENOSPC;
	goto out;
	}
	} else if (ret == -EEXIST) {
	ret = 0;
	di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
	ASSERT(di); /* logic error */
	} else if (ret) {
	goto out;
	}

	if (di && (flags & XATTR_CREATE)) {
	ret = -EEXIST;
	goto out;
	}

	if (di) {
	/*
	* We're doing a replace, and it must be atomic, that is, at
	* any point in time we have either the old or the new xattr
	* value in the tree. We don't want readers (getxattr and
	* listxattrs) to miss a value, this is specially important
	* for ACLs.
	*/
	const int slot = path->slots[0];
	struct extent_buffer *leaf = path->nodes[0];
	const u16 old_data_len = btrfs_dir_data_len(leaf, di);
	const u32 item_size = btrfs_item_size(leaf, slot);
	const u32 data_size = sizeof(*di) + name_len + size;
	unsigned long data_ptr;
	char *ptr;

	if (size > old_data_len) {
	if (btrfs_leaf_free_space(leaf) <
	(size - old_data_len)) {
	ret = -ENOSPC;
	goto out;
	}
	}

	if (old_data_len + name_len + sizeof(*di) == item_size) {
	/* No other xattrs packed in the same leaf item. */
	if (size > old_data_len)
	btrfs_extend_item(path, size - old_data_len);
	else if (size < old_data_len)
	btrfs_truncate_item(path, data_size, 1);
	} else {
	/* There are other xattrs packed in the same item. */
	ret = btrfs_delete_one_dir_name(trans, root, path, di);
	if (ret)
	goto out;
	btrfs_extend_item(path, data_size);
	}

	ptr = btrfs_item_ptr(leaf, slot, char);
	ptr += btrfs_item_size(leaf, slot) - data_size;
	di = (struct btrfs_dir_item *)ptr;
	btrfs_set_dir_data_len(leaf, di, size);
	data_ptr = ((unsigned long)(di + 1)) + name_len;
	write_extent_buffer(leaf, value, data_ptr, size);
	btrfs_mark_buffer_dirty(leaf);
	} else {
	/*
	* Insert, and we had space for the xattr, so path->slots[0] is
	* where our xattr dir_item is and btrfs_insert_xattr_item()
	* filled it.
	*/
	}
	out:
	btrfs_free_path(path);
	if (!ret) {
	set_bit(BTRFS_INODE_COPY_EVERYTHING,
	&BTRFS_I(inode)->runtime_flags);
	clear_bit(BTRFS_INODE_NO_XATTRS, &BTRFS_I(inode)->runtime_flags);
	}
	return ret;
	}

	/*
	* @value: "" makes the attribute to empty, NULL removes it
	*/
	int btrfs_setxattr_trans(struct inode inode, const char name,
	const void *value, size_t size, int flags)
	{
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct btrfs_trans_handle *trans;
	const bool start_trans = (current->journal_info == NULL);
	int ret;

	if (start_trans) {
	/*
	* 1 unit for inserting/updating/deleting the xattr
	* 1 unit for the inode item update
	*/
	trans = btrfs_start_transaction(root, 2);
	if (IS_ERR(trans))
	return PTR_ERR(trans);
	} else {
	/*
	* This can happen when smack is enabled and a directory is being
	* created. It happens through d_instantiate_new(), which calls
	* smack_d_instantiate(), which in turn calls __vfs_setxattr() to
	* set the transmute xattr (XATTR_NAME_SMACKTRANSMUTE) on the
	* inode. We have already reserved space for the xattr and inode
	* update at btrfs_mkdir(), so just use the transaction handle.
	* We don't join or start a transaction, as that will reset the
	* block_rsv of the handle and trigger a warning for the start
	* case.
	*/
	ASSERT(strncmp(name, XATTR_SECURITY_PREFIX,
	XATTR_SECURITY_PREFIX_LEN) == 0);
	trans = current->journal_info;
	}

	ret = btrfs_setxattr(trans, inode, name, value, size, flags);
	if (ret)
	goto out;

	inode_inc_iversion(inode);
	inode->i_ctime = current_time(inode);
	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
	if (ret)
	btrfs_abort_transaction(trans, ret);
	out:
	if (start_trans)
	btrfs_end_transaction(trans);
	return ret;
	}

	ssize_t btrfs_listxattr(struct dentry dentry, char buffer, size_t size)
	{
	struct btrfs_key found_key;
	struct btrfs_key key;
	struct inode *inode = d_inode(dentry);
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct btrfs_path *path;
	int iter_ret = 0;
	int ret = 0;
	size_t total_size = 0, size_left = size;

	/*
	* 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(BTRFS_I(inode));
	key.type = BTRFS_XATTR_ITEM_KEY;
	key.offset = 0;

	path = btrfs_alloc_path();
	if (!path)
	return -ENOMEM;
	path->reada = READA_FORWARD;

	/* search for our xattrs */
	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
	struct extent_buffer *leaf;
	int slot;
	struct btrfs_dir_item *di;
	u32 item_size;
	u32 cur;

	leaf = path->nodes[0];
	slot = path->slots[0];

	/* check to make sure this item is what we want */
	if (found_key.objectid != key.objectid)
	break;
	if (found_key.type > BTRFS_XATTR_ITEM_KEY)
	break;
	if (found_key.type < BTRFS_XATTR_ITEM_KEY)
	continue;

	di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
	item_size = btrfs_item_size(leaf, slot);
	cur = 0;
	while (cur < item_size) {
	u16 name_len = btrfs_dir_name_len(leaf, di);
	u16 data_len = btrfs_dir_data_len(leaf, di);
	u32 this_len = sizeof(*di) + name_len + data_len;
	unsigned long name_ptr = (unsigned long)(di + 1);

	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) {
	iter_ret = -ERANGE;
	break;
	}

	read_extent_buffer(leaf, buffer, name_ptr, name_len);
	buffer[name_len] = '\0';

	size_left -= name_len + 1;
	buffer += name_len + 1;
	next:
	cur += this_len;
	di = (struct btrfs_dir_item )((char )di + this_len);
	}
	}

	if (iter_ret < 0)
	ret = iter_ret;
	else
	ret = total_size;

	btrfs_free_path(path);

	return ret;
	}

	static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
	struct dentry unused, struct inode inode,
	const char name, void buffer, size_t size)
	{
	name = xattr_full_name(handler, name);
	return btrfs_getxattr(inode, name, buffer, size);
	}

	static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
	struct mnt_idmap *idmap,
	struct dentry unused, struct inode inode,
	const char name, const void buffer,
	size_t size, int flags)
	{
	if (btrfs_root_readonly(BTRFS_I(inode)->root))
	return -EROFS;

	name = xattr_full_name(handler, name);
	return btrfs_setxattr_trans(inode, name, buffer, size, flags);
	}

	static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
	struct mnt_idmap *idmap,
	struct dentry unused, struct inode inode,
	const char name, const void value,
	size_t size, int flags)
	{
	int ret;
	struct btrfs_trans_handle *trans;
	struct btrfs_root *root = BTRFS_I(inode)->root;

	name = xattr_full_name(handler, name);
	ret = btrfs_validate_prop(BTRFS_I(inode), name, value, size);
	if (ret)
	return ret;

	if (btrfs_ignore_prop(BTRFS_I(inode), name))
	return 0;

	trans = btrfs_start_transaction(root, 2);
	if (IS_ERR(trans))
	return PTR_ERR(trans);

	ret = btrfs_set_prop(trans, inode, name, value, size, flags);
	if (!ret) {
	inode_inc_iversion(inode);
	inode->i_ctime = current_time(inode);
	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
	if (ret)
	btrfs_abort_transaction(trans, ret);
	}

	btrfs_end_transaction(trans);

	return ret;
	}

	static const struct xattr_handler btrfs_security_xattr_handler = {
	.prefix = XATTR_SECURITY_PREFIX,
	.get = btrfs_xattr_handler_get,
	.set = btrfs_xattr_handler_set,
	};

	static const struct xattr_handler btrfs_trusted_xattr_handler = {
	.prefix = XATTR_TRUSTED_PREFIX,
	.get = btrfs_xattr_handler_get,
	.set = btrfs_xattr_handler_set,
	};

	static const struct xattr_handler btrfs_user_xattr_handler = {
	.prefix = XATTR_USER_PREFIX,
	.get = btrfs_xattr_handler_get,
	.set = btrfs_xattr_handler_set,
	};

	static const struct xattr_handler btrfs_btrfs_xattr_handler = {
	.prefix = XATTR_BTRFS_PREFIX,
	.get = btrfs_xattr_handler_get,
	.set = btrfs_xattr_handler_set_prop,
	};

	const struct xattr_handler *btrfs_xattr_handlers[] = {
	&btrfs_security_xattr_handler,
	#ifdef CONFIG_BTRFS_FS_POSIX_ACL
	&posix_acl_access_xattr_handler,
	&posix_acl_default_xattr_handler,
	#endif
	&btrfs_trusted_xattr_handler,
	&btrfs_user_xattr_handler,
	&btrfs_btrfs_xattr_handler,
	NULL,
	};

	static int btrfs_initxattrs(struct inode *inode,
	const struct xattr xattr_array, void fs_private)
	{
	struct btrfs_trans_handle *trans = fs_private;
	const struct xattr *xattr;
	unsigned int nofs_flag;
	char *name;
	int err = 0;

	/*
	* We're holding a transaction handle, so use a NOFS memory allocation
	* context to avoid deadlock if reclaim happens.
	*/
	nofs_flag = memalloc_nofs_save();
	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
	name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
	strlen(xattr->name) + 1, GFP_KERNEL);
	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;
	}
	memalloc_nofs_restore(nofs_flag);
	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);
	}