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
get_unaligned_le8(const void * p)24 static inline u8 get_unaligned_le8(const void *p)
25 {
26 return *(u8 *)p;
27 }
28
put_unaligned_le8(u8 val,void * p)29 static 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) \
53 u##bits btrfs_get_token_##bits(const struct extent_buffer *eb, \
54 const void *ptr, 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 } \
92 void btrfs_set_token_##bits(struct extent_buffer *eb, \
93 const void *ptr, unsigned long off, \
94 u##bits val, \
95 struct btrfs_map_token *token) \
96 { \
97 unsigned long part_offset = (unsigned long)ptr; \
98 unsigned long offset = part_offset + off; \
99 void *p; \
100 int err; \
101 char *kaddr; \
102 unsigned long map_start; \
103 unsigned long map_len; \
104 int size = sizeof(u##bits); \
105 \
106 if (token && token->kaddr && token->offset <= offset && \
107 token->eb == eb && \
108 (token->offset + PAGE_CACHE_SIZE >= offset + size)) { \
109 kaddr = token->kaddr; \
110 p = kaddr + part_offset - token->offset; \
111 put_unaligned_le##bits(val, p + off); \
112 return; \
113 } \
114 err = map_private_extent_buffer(eb, offset, size, \
115 &kaddr, &map_start, &map_len); \
116 if (err) { \
117 __le##bits val2; \
118 \
119 val2 = cpu_to_le##bits(val); \
120 write_extent_buffer(eb, &val2, offset, size); \
121 return; \
122 } \
123 p = kaddr + part_offset - map_start; \
124 put_unaligned_le##bits(val, p + off); \
125 if (token) { \
126 token->kaddr = kaddr; \
127 token->offset = map_start; \
128 token->eb = eb; \
129 } \
130 }
131
132 DEFINE_BTRFS_SETGET_BITS(8)
133 DEFINE_BTRFS_SETGET_BITS(16)
134 DEFINE_BTRFS_SETGET_BITS(32)
135 DEFINE_BTRFS_SETGET_BITS(64)
136
btrfs_node_key(const struct extent_buffer * eb,struct btrfs_disk_key * disk_key,int nr)137 void btrfs_node_key(const struct extent_buffer *eb,
138 struct btrfs_disk_key *disk_key, int nr)
139 {
140 unsigned long ptr = btrfs_node_key_ptr_offset(nr);
141 read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
142 struct btrfs_key_ptr, key, disk_key);
143 }
144