1/*
2 * Copyright (C) 2007 Oracle.  All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public
6 * License v2 as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
11 * General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public
14 * License along with this program; if not, write to the
15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16 * Boston, MA 021110-1307, USA.
17 */
18
19#include <linux/highmem.h>
20#include <asm/unaligned.h>
21
22#include "ctree.h"
23
24static inline u8 get_unaligned_le8(const void *p)
25{
26       return *(u8 *)p;
27}
28
29static inline void put_unaligned_le8(u8 val, void *p)
30{
31       *(u8 *)p = val;
32}
33
34/*
35 * this is some deeply nasty code.
36 *
37 * The end result is that anyone who #includes ctree.h gets a
38 * declaration for the btrfs_set_foo functions and btrfs_foo functions,
39 * which are wappers of btrfs_set_token_#bits functions and
40 * btrfs_get_token_#bits functions, which are defined in this file.
41 *
42 * These setget functions do all the extent_buffer related mapping
43 * required to efficiently read and write specific fields in the extent
44 * buffers.  Every pointer to metadata items in btrfs is really just
45 * an unsigned long offset into the extent buffer which has been
46 * cast to a specific type.  This gives us all the gcc type checking.
47 *
48 * The extent buffer api is used to do the page spanning work required to
49 * have a metadata blocksize different from the page size.
50 */
51
52#define DEFINE_BTRFS_SETGET_BITS(bits)					\
53u##bits btrfs_get_token_##bits(struct extent_buffer *eb, void *ptr,	\
54			       unsigned long off,			\
55			       struct btrfs_map_token *token)		\
56{									\
57	unsigned long part_offset = (unsigned long)ptr;			\
58	unsigned long offset = part_offset + off;			\
59	void *p;							\
60	int err;							\
61	char *kaddr;							\
62	unsigned long map_start;					\
63	unsigned long map_len;						\
64	int size = sizeof(u##bits);					\
65	u##bits res;							\
66									\
67	if (token && token->kaddr && token->offset <= offset &&		\
68	    token->eb == eb &&						\
69	   (token->offset + PAGE_CACHE_SIZE >= offset + size)) {	\
70		kaddr = token->kaddr;					\
71		p = kaddr + part_offset - token->offset;		\
72		res = get_unaligned_le##bits(p + off);			\
73		return res;						\
74	}								\
75	err = map_private_extent_buffer(eb, offset, size,		\
76					&kaddr, &map_start, &map_len);	\
77	if (err) {							\
78		__le##bits leres;					\
79									\
80		read_extent_buffer(eb, &leres, offset, size);		\
81		return le##bits##_to_cpu(leres);			\
82	}								\
83	p = kaddr + part_offset - map_start;				\
84	res = get_unaligned_le##bits(p + off);				\
85	if (token) {							\
86		token->kaddr = kaddr;					\
87		token->offset = map_start;				\
88		token->eb = eb;						\
89	}								\
90	return res;							\
91}									\
92void btrfs_set_token_##bits(struct extent_buffer *eb,			\
93			    void *ptr, unsigned long off, u##bits val,	\
94			    struct btrfs_map_token *token)		\
95{									\
96	unsigned long part_offset = (unsigned long)ptr;			\
97	unsigned long offset = part_offset + off;			\
98	void *p;							\
99	int err;							\
100	char *kaddr;							\
101	unsigned long map_start;					\
102	unsigned long map_len;						\
103	int size = sizeof(u##bits);					\
104									\
105	if (token && token->kaddr && token->offset <= offset &&		\
106	    token->eb == eb &&						\
107	   (token->offset + PAGE_CACHE_SIZE >= offset + size)) {	\
108		kaddr = token->kaddr;					\
109		p = kaddr + part_offset - token->offset;		\
110		put_unaligned_le##bits(val, p + off);			\
111		return;							\
112	}								\
113	err = map_private_extent_buffer(eb, offset, size,		\
114			&kaddr, &map_start, &map_len);			\
115	if (err) {							\
116		__le##bits val2;					\
117									\
118		val2 = cpu_to_le##bits(val);				\
119		write_extent_buffer(eb, &val2, offset, size);		\
120		return;							\
121	}								\
122	p = kaddr + part_offset - map_start;				\
123	put_unaligned_le##bits(val, p + off);				\
124	if (token) {							\
125		token->kaddr = kaddr;					\
126		token->offset = map_start;				\
127		token->eb = eb;						\
128	}								\
129}
130
131DEFINE_BTRFS_SETGET_BITS(8)
132DEFINE_BTRFS_SETGET_BITS(16)
133DEFINE_BTRFS_SETGET_BITS(32)
134DEFINE_BTRFS_SETGET_BITS(64)
135
136void btrfs_node_key(struct extent_buffer *eb,
137		    struct btrfs_disk_key *disk_key, int nr)
138{
139	unsigned long ptr = btrfs_node_key_ptr_offset(nr);
140	read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
141		       struct btrfs_key_ptr, key, disk_key);
142}
143