Root/fs/btrfs/struct-funcs.c

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}
140

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