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-rw-r--r--fs/btrfs/struct-funcs.c139
1 files changed, 139 insertions, 0 deletions
diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c
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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
21/* this is some deeply nasty code. ctree.h has a different
22 * definition for this BTRFS_SETGET_FUNCS macro, behind a #ifndef
23 *
24 * The end result is that anyone who #includes ctree.h gets a
25 * declaration for the btrfs_set_foo functions and btrfs_foo functions
26 *
27 * This file declares the macros and then #includes ctree.h, which results
28 * in cpp creating the function here based on the template below.
29 *
30 * These setget functions do all the extent_buffer related mapping
31 * required to efficiently read and write specific fields in the extent
32 * buffers. Every pointer to metadata items in btrfs is really just
33 * an unsigned long offset into the extent buffer which has been
34 * cast to a specific type. This gives us all the gcc type checking.
35 *
36 * The extent buffer api is used to do all the kmapping and page
37 * spanning work required to get extent buffers in highmem and have
38 * a metadata blocksize different from the page size.
39 *
40 * The macro starts with a simple function prototype declaration so that
41 * sparse won't complain about it being static.
42 */
43
44#define BTRFS_SETGET_FUNCS(name, type, member, bits) \
45u##bits btrfs_##name(struct extent_buffer *eb, type *s); \
46void btrfs_set_##name(struct extent_buffer *eb, type *s, u##bits val); \
47u##bits btrfs_##name(struct extent_buffer *eb, \
48 type *s) \
49{ \
50 unsigned long part_offset = (unsigned long)s; \
51 unsigned long offset = part_offset + offsetof(type, member); \
52 type *p; \
53 /* ugly, but we want the fast path here */ \
54 if (eb->map_token && offset >= eb->map_start && \
55 offset + sizeof(((type *)0)->member) <= eb->map_start + \
56 eb->map_len) { \
57 p = (type *)(eb->kaddr + part_offset - eb->map_start); \
58 return le##bits##_to_cpu(p->member); \
59 } \
60 { \
61 int err; \
62 char *map_token; \
63 char *kaddr; \
64 int unmap_on_exit = (eb->map_token == NULL); \
65 unsigned long map_start; \
66 unsigned long map_len; \
67 u##bits res; \
68 err = map_extent_buffer(eb, offset, \
69 sizeof(((type *)0)->member), \
70 &map_token, &kaddr, \
71 &map_start, &map_len, KM_USER1); \
72 if (err) { \
73 __le##bits leres; \
74 read_eb_member(eb, s, type, member, &leres); \
75 return le##bits##_to_cpu(leres); \
76 } \
77 p = (type *)(kaddr + part_offset - map_start); \
78 res = le##bits##_to_cpu(p->member); \
79 if (unmap_on_exit) \
80 unmap_extent_buffer(eb, map_token, KM_USER1); \
81 return res; \
82 } \
83} \
84void btrfs_set_##name(struct extent_buffer *eb, \
85 type *s, u##bits val) \
86{ \
87 unsigned long part_offset = (unsigned long)s; \
88 unsigned long offset = part_offset + offsetof(type, member); \
89 type *p; \
90 /* ugly, but we want the fast path here */ \
91 if (eb->map_token && offset >= eb->map_start && \
92 offset + sizeof(((type *)0)->member) <= eb->map_start + \
93 eb->map_len) { \
94 p = (type *)(eb->kaddr + part_offset - eb->map_start); \
95 p->member = cpu_to_le##bits(val); \
96 return; \
97 } \
98 { \
99 int err; \
100 char *map_token; \
101 char *kaddr; \
102 int unmap_on_exit = (eb->map_token == NULL); \
103 unsigned long map_start; \
104 unsigned long map_len; \
105 err = map_extent_buffer(eb, offset, \
106 sizeof(((type *)0)->member), \
107 &map_token, &kaddr, \
108 &map_start, &map_len, KM_USER1); \
109 if (err) { \
110 __le##bits val2; \
111 val2 = cpu_to_le##bits(val); \
112 write_eb_member(eb, s, type, member, &val2); \
113 return; \
114 } \
115 p = (type *)(kaddr + part_offset - map_start); \
116 p->member = cpu_to_le##bits(val); \
117 if (unmap_on_exit) \
118 unmap_extent_buffer(eb, map_token, KM_USER1); \
119 } \
120}
121
122#include "ctree.h"
123
124void btrfs_node_key(struct extent_buffer *eb,
125 struct btrfs_disk_key *disk_key, int nr)
126{
127 unsigned long ptr = btrfs_node_key_ptr_offset(nr);
128 if (eb->map_token && ptr >= eb->map_start &&
129 ptr + sizeof(*disk_key) <= eb->map_start + eb->map_len) {
130 memcpy(disk_key, eb->kaddr + ptr - eb->map_start,
131 sizeof(*disk_key));
132 return;
133 } else if (eb->map_token) {
134 unmap_extent_buffer(eb, eb->map_token, KM_USER1);
135 eb->map_token = NULL;
136 }
137 read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
138 struct btrfs_key_ptr, key, disk_key);
139}
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