struct-funcs.c
4.49 KB
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/*
* Copyright (C) 2007 Oracle. All rights reserved.
*
* 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/highmem.h>
#include <asm/unaligned.h>
#include "ctree.h"
static inline u8 get_unaligned_le8(const void *p)
{
return *(u8 *)p;
}
static inline void put_unaligned_le8(u8 val, void *p)
{
*(u8 *)p = val;
}
/*
* this is some deeply nasty code.
*
* The end result is that anyone who #includes ctree.h gets a
* declaration for the btrfs_set_foo functions and btrfs_foo functions,
* which are wappers of btrfs_set_token_#bits functions and
* btrfs_get_token_#bits functions, which are defined in this file.
*
* These setget functions do all the extent_buffer related mapping
* required to efficiently read and write specific fields in the extent
* buffers. Every pointer to metadata items in btrfs is really just
* an unsigned long offset into the extent buffer which has been
* cast to a specific type. This gives us all the gcc type checking.
*
* The extent buffer api is used to do the page spanning work required to
* have a metadata blocksize different from the page size.
*/
#define DEFINE_BTRFS_SETGET_BITS(bits) \
u##bits btrfs_get_token_##bits(struct extent_buffer *eb, void *ptr, \
unsigned long off, \
struct btrfs_map_token *token) \
{ \
unsigned long part_offset = (unsigned long)ptr; \
unsigned long offset = part_offset + off; \
void *p; \
int err; \
char *kaddr; \
unsigned long map_start; \
unsigned long map_len; \
int size = sizeof(u##bits); \
u##bits res; \
\
if (token && token->kaddr && token->offset <= offset && \
token->eb == eb && \
(token->offset + PAGE_CACHE_SIZE >= offset + size)) { \
kaddr = token->kaddr; \
p = kaddr + part_offset - token->offset; \
res = get_unaligned_le##bits(p + off); \
return res; \
} \
err = map_private_extent_buffer(eb, offset, size, \
&kaddr, &map_start, &map_len); \
if (err) { \
__le##bits leres; \
\
read_extent_buffer(eb, &leres, offset, size); \
return le##bits##_to_cpu(leres); \
} \
p = kaddr + part_offset - map_start; \
res = get_unaligned_le##bits(p + off); \
if (token) { \
token->kaddr = kaddr; \
token->offset = map_start; \
token->eb = eb; \
} \
return res; \
} \
void btrfs_set_token_##bits(struct extent_buffer *eb, \
void *ptr, unsigned long off, u##bits val, \
struct btrfs_map_token *token) \
{ \
unsigned long part_offset = (unsigned long)ptr; \
unsigned long offset = part_offset + off; \
void *p; \
int err; \
char *kaddr; \
unsigned long map_start; \
unsigned long map_len; \
int size = sizeof(u##bits); \
\
if (token && token->kaddr && token->offset <= offset && \
token->eb == eb && \
(token->offset + PAGE_CACHE_SIZE >= offset + size)) { \
kaddr = token->kaddr; \
p = kaddr + part_offset - token->offset; \
put_unaligned_le##bits(val, p + off); \
return; \
} \
err = map_private_extent_buffer(eb, offset, size, \
&kaddr, &map_start, &map_len); \
if (err) { \
__le##bits val2; \
\
val2 = cpu_to_le##bits(val); \
write_extent_buffer(eb, &val2, offset, size); \
return; \
} \
p = kaddr + part_offset - map_start; \
put_unaligned_le##bits(val, p + off); \
if (token) { \
token->kaddr = kaddr; \
token->offset = map_start; \
token->eb = eb; \
} \
}
DEFINE_BTRFS_SETGET_BITS(8)
DEFINE_BTRFS_SETGET_BITS(16)
DEFINE_BTRFS_SETGET_BITS(32)
DEFINE_BTRFS_SETGET_BITS(64)
void btrfs_node_key(struct extent_buffer *eb,
struct btrfs_disk_key *disk_key, int nr)
{
unsigned long ptr = btrfs_node_key_ptr_offset(nr);
read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
struct btrfs_key_ptr, key, disk_key);
}