fs/btrfs/props.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (C) 2014 Filipe David Borba Manana <fdmanana@gmail.com>
  *
  * 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/hashtable.h>
 #include "props.h"
 #include "btrfs_inode.h"
 #include "hash.h"
 #include "transaction.h"
 #include "xattr.h"

 #define BTRFS_PROP_HANDLERS_HT_BITS 8
 static DEFINE_HASHTABLE(prop_handlers_ht, BTRFS_PROP_HANDLERS_HT_BITS);

 struct prop_handler {
 	struct hlist_node node;
 	const char *xattr_name;
 	int (*validate)(const char *value, size_t len);
 	int (*apply)(struct inode *inode, const char *value, size_t len);
 	const char *(*extract)(struct inode *inode);
 	int inheritable;
 };

 static int prop_compression_validate(const char *value, size_t len);
 static int prop_compression_apply(struct inode *inode,
 				  const char *value,
 				  size_t len);
 static const char *prop_compression_extract(struct inode *inode);

 static struct prop_handler prop_handlers[] = {
 	{
 		.xattr_name = XATTR_BTRFS_PREFIX "compression",
 		.validate = prop_compression_validate,
 		.apply = prop_compression_apply,
 		.extract = prop_compression_extract,
 		.inheritable = 1
 	},
 	{
 		.xattr_name = NULL
 	}
 };

 void __init btrfs_props_init(void)
 {
 	struct prop_handler *p;

 	hash_init(prop_handlers_ht);

 	for (p = &prop_handlers[0]; p->xattr_name; p++) {
 		u64 h = btrfs_name_hash(p->xattr_name, strlen(p->xattr_name));

 		hash_add(prop_handlers_ht, &p->node, h);
 	}
 }

 static const struct hlist_head *find_prop_handlers_by_hash(const u64 hash)
 {
 	struct hlist_head *h;

 	h = &prop_handlers_ht[hash_min(hash, BTRFS_PROP_HANDLERS_HT_BITS)];
 	if (hlist_empty(h))
 		return NULL;

 	return h;
 }

 static const struct prop_handler *
 find_prop_handler(const char *name,
 		  const struct hlist_head *handlers)
 {
 	struct prop_handler *h;

 	if (!handlers) {
 		u64 hash = btrfs_name_hash(name, strlen(name));

 		handlers = find_prop_handlers_by_hash(hash);
 		if (!handlers)
 			return NULL;
 	}

 	hlist_for_each_entry(h, handlers, node)
 		if (!strcmp(h->xattr_name, name))
 			return h;

 	return NULL;
 }

 static int __btrfs_set_prop(struct btrfs_trans_handle *trans,
 			    struct inode *inode,
 			    const char *name,
 			    const char *value,
 			    size_t value_len,
 			    int flags)
 {
 	const struct prop_handler *handler;
 	int ret;

 	if (strlen(name) <= XATTR_BTRFS_PREFIX_LEN)
 		return -EINVAL;

 	handler = find_prop_handler(name, NULL);
 	if (!handler)
 		return -EINVAL;

 	if (value_len == 0) {
 		ret = __btrfs_setxattr(trans, inode, handler->xattr_name,
 				       NULL, 0, flags);
 		if (ret)
 			return ret;

 		ret = handler->apply(inode, NULL, 0);
 		ASSERT(ret == 0);

 		return ret;
 	}

 	ret = handler->validate(value, value_len);
 	if (ret)
 		return ret;
 	ret = __btrfs_setxattr(trans, inode, handler->xattr_name,
 			       value, value_len, flags);
 	if (ret)
 		return ret;
 	ret = handler->apply(inode, value, value_len);
 	if (ret) {
 		__btrfs_setxattr(trans, inode, handler->xattr_name,
 				 NULL, 0, flags);
 		return ret;
 	}

 	set_bit(BTRFS_INODE_HAS_PROPS, &BTRFS_I(inode)->runtime_flags);

 	return 0;
 }

 int btrfs_set_prop(struct inode *inode,
 		   const char *name,
 		   const char *value,
 		   size_t value_len,
 		   int flags)
 {
 	return __btrfs_set_prop(NULL, inode, name, value, value_len, flags);
 }

 static int iterate_object_props(struct btrfs_root *root,
 				struct btrfs_path *path,
 				u64 objectid,
 				void (*iterator)(void *,
 						 const struct prop_handler *,
 						 const char *,
 						 size_t),
 				void *ctx)
 {
 	int ret;
 	char *name_buf = NULL;
 	char *value_buf = NULL;
 	int name_buf_len = 0;
 	int value_buf_len = 0;

 	while (1) {
 		struct btrfs_key key;
 		struct btrfs_dir_item *di;
 		struct extent_buffer *leaf;
 		u32 total_len, cur, this_len;
 		int slot;
 		const struct hlist_head *handlers;

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

 		if (slot >= btrfs_header_nritems(leaf)) {
 			ret = btrfs_next_leaf(root, path);
 			if (ret < 0)
 				goto out;
 			else if (ret > 0)
 				break;
 			continue;
 		}

 		btrfs_item_key_to_cpu(leaf, &key, slot);
 		if (key.objectid != objectid)
 			break;
 		if (key.type != BTRFS_XATTR_ITEM_KEY)
 			break;

 		handlers = find_prop_handlers_by_hash(key.offset);
 		if (!handlers)
 			goto next_slot;

 		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 		cur = 0;
 		total_len = btrfs_item_size_nr(leaf, slot);

 		while (cur < total_len) {
 			u32 name_len = btrfs_dir_name_len(leaf, di);
 			u32 data_len = btrfs_dir_data_len(leaf, di);
 			unsigned long name_ptr, data_ptr;
 			const struct prop_handler *handler;

 			this_len = sizeof(*di) + name_len + data_len;
 			name_ptr = (unsigned long)(di + 1);
 			data_ptr = name_ptr + name_len;

 			if (name_len <= XATTR_BTRFS_PREFIX_LEN ||
 			    memcmp_extent_buffer(leaf, XATTR_BTRFS_PREFIX,
 						 name_ptr,
 						 XATTR_BTRFS_PREFIX_LEN))
 				goto next_dir_item;

 			if (name_len >= name_buf_len) {
 				kfree(name_buf);
 				name_buf_len = name_len + 1;
 				name_buf = kmalloc(name_buf_len, GFP_NOFS);
 				if (!name_buf) {
 					ret = -ENOMEM;
 					goto out;
 				}
 			}
 			read_extent_buffer(leaf, name_buf, name_ptr, name_len);
 			name_buf[name_len] = '\0';

 			handler = find_prop_handler(name_buf, handlers);
 			if (!handler)
 				goto next_dir_item;

 			if (data_len > value_buf_len) {
 				kfree(value_buf);
 				value_buf_len = data_len;
 				value_buf = kmalloc(data_len, GFP_NOFS);
 				if (!value_buf) {
 					ret = -ENOMEM;
 					goto out;
 				}
 			}
 			read_extent_buffer(leaf, value_buf, data_ptr, data_len);

 			iterator(ctx, handler, value_buf, data_len);
 next_dir_item:
 			cur += this_len;
 			di = (struct btrfs_dir_item *)((char *) di + this_len);
 		}

 next_slot:
 		path->slots[0]++;
 	}

 	ret = 0;
 out:
 	btrfs_release_path(path);
 	kfree(name_buf);
 	kfree(value_buf);

 	return ret;
 }

 static void inode_prop_iterator(void *ctx,
 				const struct prop_handler *handler,
 				const char *value,
 				size_t len)
 {
 	struct inode *inode = ctx;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	int ret;

 	ret = handler->apply(inode, value, len);
 	if (unlikely(ret))
 		btrfs_warn(root->fs_info,
 			   "error applying prop %s to ino %llu (root %llu): %d",
 			   handler->xattr_name, btrfs_ino(inode),
 			   root->root_key.objectid, ret);
 	else
 		set_bit(BTRFS_INODE_HAS_PROPS, &BTRFS_I(inode)->runtime_flags);
 }

 int btrfs_load_inode_props(struct inode *inode, struct btrfs_path *path)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	u64 ino = btrfs_ino(inode);
 	int ret;

 	ret = iterate_object_props(root, path, ino, inode_prop_iterator, inode);

 	return ret;
 }

 static int inherit_props(struct btrfs_trans_handle *trans,
 			 struct inode *inode,
 			 struct inode *parent)
 {
 	const struct prop_handler *h;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	int ret;

 	if (!test_bit(BTRFS_INODE_HAS_PROPS,
 		      &BTRFS_I(parent)->runtime_flags))
 		return 0;

 	for (h = &prop_handlers[0]; h->xattr_name; h++) {
 		const char *value;
 		u64 num_bytes;

 		if (!h->inheritable)
 			continue;

 		value = h->extract(parent);
 		if (!value)
 			continue;

 		num_bytes = btrfs_calc_trans_metadata_size(root, 1);
 		ret = btrfs_block_rsv_add(root, trans->block_rsv,
 					  num_bytes, BTRFS_RESERVE_NO_FLUSH);
 		if (ret)
 			goto out;
 		ret = __btrfs_set_prop(trans, inode, h->xattr_name,
 				       value, strlen(value), 0);
 		btrfs_block_rsv_release(root, trans->block_rsv, num_bytes);
 		if (ret)
 			goto out;
 	}
 	ret = 0;
 out:
 	return ret;
 }

 int btrfs_inode_inherit_props(struct btrfs_trans_handle *trans,
 			      struct inode *inode,
 			      struct inode *dir)
 {
 	if (!dir)
 		return 0;

 	return inherit_props(trans, inode, dir);
 }

 int btrfs_subvol_inherit_props(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *root,
 			       struct btrfs_root *parent_root)
 {
 	struct btrfs_key key;
 	struct inode *parent_inode, *child_inode;
 	int ret;

 	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
 	key.type = BTRFS_INODE_ITEM_KEY;
 	key.offset = 0;

 	parent_inode = btrfs_iget(parent_root->fs_info->sb, &key,
 				  parent_root, NULL);
 	if (IS_ERR(parent_inode))
 		return PTR_ERR(parent_inode);

 	child_inode = btrfs_iget(root->fs_info->sb, &key, root, NULL);
 	if (IS_ERR(child_inode)) {
 		iput(parent_inode);
 		return PTR_ERR(child_inode);
 	}

 	ret = inherit_props(trans, child_inode, parent_inode);
 	iput(child_inode);
 	iput(parent_inode);

 	return ret;
 }

 static int prop_compression_validate(const char *value, size_t len)
 {
 	if (!strncmp("lzo", value, len))
 		return 0;
 	else if (!strncmp("zlib", value, len))
 		return 0;

 	return -EINVAL;
 }

 static int prop_compression_apply(struct inode *inode,
 				  const char *value,
 				  size_t len)
 {
 	int type;

 	if (len == 0) {
 		BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS;
 		BTRFS_I(inode)->flags &= ~BTRFS_INODE_COMPRESS;
 		BTRFS_I(inode)->force_compress = BTRFS_COMPRESS_NONE;

 		return 0;
 	}

 	if (!strncmp("lzo", value, len))
 		type = BTRFS_COMPRESS_LZO;
 	else if (!strncmp("zlib", value, len))
 		type = BTRFS_COMPRESS_ZLIB;
 	else
 		return -EINVAL;

 	BTRFS_I(inode)->flags &= ~BTRFS_INODE_NOCOMPRESS;
 	BTRFS_I(inode)->flags |= BTRFS_INODE_COMPRESS;
 	BTRFS_I(inode)->force_compress = type;

 	return 0;
 }

 static const char *prop_compression_extract(struct inode *inode)
 {
 	switch (BTRFS_I(inode)->force_compress) {
 	case BTRFS_COMPRESS_ZLIB:
 		return "zlib";
 	case BTRFS_COMPRESS_LZO:
 		return "lzo";
 	}

 	return NULL;
 }
	/*
	* Copyright (C) 2014 Filipe David Borba Manana <fdmanana@gmail.com>
	*
	* 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/hashtable.h>
	#include "props.h"
	#include "btrfs_inode.h"
	#include "hash.h"
	#include "transaction.h"
	#include "xattr.h"

	#define BTRFS_PROP_HANDLERS_HT_BITS 8
	static DEFINE_HASHTABLE(prop_handlers_ht, BTRFS_PROP_HANDLERS_HT_BITS);

	struct prop_handler {
	struct hlist_node node;
	const char *xattr_name;
	int (validate)(const char value, size_t len);
	int (apply)(struct inode inode, const char *value, size_t len);
	const char (extract)(struct inode *inode);
	int inheritable;
	};

	static int prop_compression_validate(const char *value, size_t len);
	static int prop_compression_apply(struct inode *inode,
	const char *value,
	size_t len);
	static const char prop_compression_extract(struct inode inode);

	static struct prop_handler prop_handlers[] = {
	{
	.xattr_name = XATTR_BTRFS_PREFIX "compression",
	.validate = prop_compression_validate,
	.apply = prop_compression_apply,
	.extract = prop_compression_extract,
	.inheritable = 1
	},
	{
	.xattr_name = NULL
	}
	};

	void __init btrfs_props_init(void)
	{
	struct prop_handler *p;

	hash_init(prop_handlers_ht);

	for (p = &prop_handlers[0]; p->xattr_name; p++) {
	u64 h = btrfs_name_hash(p->xattr_name, strlen(p->xattr_name));

	hash_add(prop_handlers_ht, &p->node, h);
	}
	}

	static const struct hlist_head *find_prop_handlers_by_hash(const u64 hash)
	{
	struct hlist_head *h;

	h = &prop_handlers_ht[hash_min(hash, BTRFS_PROP_HANDLERS_HT_BITS)];
	if (hlist_empty(h))
	return NULL;

	return h;
	}

	static const struct prop_handler *
	find_prop_handler(const char *name,
	const struct hlist_head *handlers)
	{
	struct prop_handler *h;

	if (!handlers) {
	u64 hash = btrfs_name_hash(name, strlen(name));

	handlers = find_prop_handlers_by_hash(hash);
	if (!handlers)
	return NULL;
	}

	hlist_for_each_entry(h, handlers, node)
	if (!strcmp(h->xattr_name, name))
	return h;

	return NULL;
	}

	static int __btrfs_set_prop(struct btrfs_trans_handle *trans,
	struct inode *inode,
	const char *name,
	const char *value,
	size_t value_len,
	int flags)
	{
	const struct prop_handler *handler;
	int ret;

	if (strlen(name) <= XATTR_BTRFS_PREFIX_LEN)
	return -EINVAL;

	handler = find_prop_handler(name, NULL);
	if (!handler)
	return -EINVAL;

	if (value_len == 0) {
	ret = __btrfs_setxattr(trans, inode, handler->xattr_name,
	NULL, 0, flags);
	if (ret)
	return ret;

	ret = handler->apply(inode, NULL, 0);
	ASSERT(ret == 0);

	return ret;
	}

	ret = handler->validate(value, value_len);
	if (ret)
	return ret;
	ret = __btrfs_setxattr(trans, inode, handler->xattr_name,
	value, value_len, flags);
	if (ret)
	return ret;
	ret = handler->apply(inode, value, value_len);
	if (ret) {
	__btrfs_setxattr(trans, inode, handler->xattr_name,
	NULL, 0, flags);
	return ret;
	}

	set_bit(BTRFS_INODE_HAS_PROPS, &BTRFS_I(inode)->runtime_flags);

	return 0;
	}

	int btrfs_set_prop(struct inode *inode,
	const char *name,
	const char *value,
	size_t value_len,
	int flags)
	{
	return __btrfs_set_prop(NULL, inode, name, value, value_len, flags);
	}

	static int iterate_object_props(struct btrfs_root *root,
	struct btrfs_path *path,
	u64 objectid,
	void (iterator)(void ,
	const struct prop_handler *,
	const char *,
	size_t),
	void *ctx)
	{
	int ret;
	char *name_buf = NULL;
	char *value_buf = NULL;
	int name_buf_len = 0;
	int value_buf_len = 0;

	while (1) {
	struct btrfs_key key;
	struct btrfs_dir_item *di;
	struct extent_buffer *leaf;
	u32 total_len, cur, this_len;
	int slot;
	const struct hlist_head *handlers;

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

	if (slot >= btrfs_header_nritems(leaf)) {
	ret = btrfs_next_leaf(root, path);
	if (ret < 0)
	goto out;
	else if (ret > 0)
	break;
	continue;
	}

	btrfs_item_key_to_cpu(leaf, &key, slot);
	if (key.objectid != objectid)
	break;
	if (key.type != BTRFS_XATTR_ITEM_KEY)
	break;

	handlers = find_prop_handlers_by_hash(key.offset);
	if (!handlers)
	goto next_slot;

	di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
	cur = 0;
	total_len = btrfs_item_size_nr(leaf, slot);

	while (cur < total_len) {
	u32 name_len = btrfs_dir_name_len(leaf, di);
	u32 data_len = btrfs_dir_data_len(leaf, di);
	unsigned long name_ptr, data_ptr;
	const struct prop_handler *handler;

	this_len = sizeof(*di) + name_len + data_len;
	name_ptr = (unsigned long)(di + 1);
	data_ptr = name_ptr + name_len;

	if (name_len <= XATTR_BTRFS_PREFIX_LEN \|\|
	memcmp_extent_buffer(leaf, XATTR_BTRFS_PREFIX,
	name_ptr,
	XATTR_BTRFS_PREFIX_LEN))
	goto next_dir_item;

	if (name_len >= name_buf_len) {
	kfree(name_buf);
	name_buf_len = name_len + 1;
	name_buf = kmalloc(name_buf_len, GFP_NOFS);
	if (!name_buf) {
	ret = -ENOMEM;
	goto out;
	}
	}
	read_extent_buffer(leaf, name_buf, name_ptr, name_len);
	name_buf[name_len] = '\0';

	handler = find_prop_handler(name_buf, handlers);
	if (!handler)
	goto next_dir_item;

	if (data_len > value_buf_len) {
	kfree(value_buf);
	value_buf_len = data_len;
	value_buf = kmalloc(data_len, GFP_NOFS);
	if (!value_buf) {
	ret = -ENOMEM;
	goto out;
	}
	}
	read_extent_buffer(leaf, value_buf, data_ptr, data_len);

	iterator(ctx, handler, value_buf, data_len);
	next_dir_item:
	cur += this_len;
	di = (struct btrfs_dir_item )((char ) di + this_len);
	}

	next_slot:
	path->slots[0]++;
	}

	ret = 0;
	out:
	btrfs_release_path(path);
	kfree(name_buf);
	kfree(value_buf);

	return ret;
	}

	static void inode_prop_iterator(void *ctx,
	const struct prop_handler *handler,
	const char *value,
	size_t len)
	{
	struct inode *inode = ctx;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	int ret;

	ret = handler->apply(inode, value, len);
	if (unlikely(ret))
	btrfs_warn(root->fs_info,
	"error applying prop %s to ino %llu (root %llu): %d",
	handler->xattr_name, btrfs_ino(inode),
	root->root_key.objectid, ret);
	else
	set_bit(BTRFS_INODE_HAS_PROPS, &BTRFS_I(inode)->runtime_flags);
	}

	int btrfs_load_inode_props(struct inode inode, struct btrfs_path path)
	{
	struct btrfs_root *root = BTRFS_I(inode)->root;
	u64 ino = btrfs_ino(inode);
	int ret;

	ret = iterate_object_props(root, path, ino, inode_prop_iterator, inode);

	return ret;
	}

	static int inherit_props(struct btrfs_trans_handle *trans,
	struct inode *inode,
	struct inode *parent)
	{
	const struct prop_handler *h;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	int ret;

	if (!test_bit(BTRFS_INODE_HAS_PROPS,
	&BTRFS_I(parent)->runtime_flags))
	return 0;

	for (h = &prop_handlers[0]; h->xattr_name; h++) {
	const char *value;
	u64 num_bytes;

	if (!h->inheritable)
	continue;

	value = h->extract(parent);
	if (!value)
	continue;

	num_bytes = btrfs_calc_trans_metadata_size(root, 1);
	ret = btrfs_block_rsv_add(root, trans->block_rsv,
	num_bytes, BTRFS_RESERVE_NO_FLUSH);
	if (ret)
	goto out;
	ret = __btrfs_set_prop(trans, inode, h->xattr_name,
	value, strlen(value), 0);
	btrfs_block_rsv_release(root, trans->block_rsv, num_bytes);
	if (ret)
	goto out;
	}
	ret = 0;
	out:
	return ret;
	}

	int btrfs_inode_inherit_props(struct btrfs_trans_handle *trans,
	struct inode *inode,
	struct inode *dir)
	{
	if (!dir)
	return 0;

	return inherit_props(trans, inode, dir);
	}

	int btrfs_subvol_inherit_props(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_root *parent_root)
	{
	struct btrfs_key key;
	struct inode parent_inode, child_inode;
	int ret;

	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
	key.type = BTRFS_INODE_ITEM_KEY;
	key.offset = 0;

	parent_inode = btrfs_iget(parent_root->fs_info->sb, &key,
	parent_root, NULL);
	if (IS_ERR(parent_inode))
	return PTR_ERR(parent_inode);

	child_inode = btrfs_iget(root->fs_info->sb, &key, root, NULL);
	if (IS_ERR(child_inode)) {
	iput(parent_inode);
	return PTR_ERR(child_inode);
	}

	ret = inherit_props(trans, child_inode, parent_inode);
	iput(child_inode);
	iput(parent_inode);

	return ret;
	}

	static int prop_compression_validate(const char *value, size_t len)
	{
	if (!strncmp("lzo", value, len))
	return 0;
	else if (!strncmp("zlib", value, len))
	return 0;

	return -EINVAL;
	}

	static int prop_compression_apply(struct inode *inode,
	const char *value,
	size_t len)
	{
	int type;

	if (len == 0) {
	BTRFS_I(inode)->flags \|= BTRFS_INODE_NOCOMPRESS;
	BTRFS_I(inode)->flags &= ~BTRFS_INODE_COMPRESS;
	BTRFS_I(inode)->force_compress = BTRFS_COMPRESS_NONE;

	return 0;
	}

	if (!strncmp("lzo", value, len))
	type = BTRFS_COMPRESS_LZO;
	else if (!strncmp("zlib", value, len))
	type = BTRFS_COMPRESS_ZLIB;
	else
	return -EINVAL;

	BTRFS_I(inode)->flags &= ~BTRFS_INODE_NOCOMPRESS;
	BTRFS_I(inode)->flags \|= BTRFS_INODE_COMPRESS;
	BTRFS_I(inode)->force_compress = type;

	return 0;
	}

	static const char prop_compression_extract(struct inode inode)
	{
	switch (BTRFS_I(inode)->force_compress) {
	case BTRFS_COMPRESS_ZLIB:
	return "zlib";
	case BTRFS_COMPRESS_LZO:
	return "lzo";
	}

	return NULL;
	}