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linux-next/fs/btrfs/struct-funcs.c
David Sterba 870b388db0 btrfs: preset set/get token with first page and drop condition
All the set/get helpers first check if the token contains a cached
address. After first use the address is always valid, but the extra
check is done for each call.

The token initialization can optimistically set it to the first extent
buffer page, that we know always exists. Then the condition in all
btrfs_token_*/btrfs_set_token_* can be simplified by removing the
address check from the condition, but for development the assertion
still makes sure it's valid.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-05-25 11:25:32 +02:00

175 lines
5.3 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2007 Oracle. All rights reserved.
*/
#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 wrappers 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.
*
* There are 2 variants defined, one with a token pointer and one without.
*/
#define DEFINE_BTRFS_SETGET_BITS(bits) \
u##bits btrfs_get_token_##bits(struct btrfs_map_token *token, \
const void *ptr, unsigned long off) \
{ \
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; \
\
ASSERT(token); \
ASSERT(token->kaddr); \
if (token->offset <= offset && \
(token->offset + PAGE_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(token->eb, offset, size, \
&kaddr, &map_start, &map_len); \
if (err) { \
__le##bits leres; \
\
read_extent_buffer(token->eb, &leres, offset, size); \
return le##bits##_to_cpu(leres); \
} \
p = kaddr + part_offset - map_start; \
res = get_unaligned_le##bits(p + off); \
token->kaddr = kaddr; \
token->offset = map_start; \
return res; \
} \
u##bits btrfs_get_##bits(const struct extent_buffer *eb, \
const void *ptr, unsigned long off) \
{ \
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; \
\
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); \
return res; \
} \
void btrfs_set_token_##bits(struct btrfs_map_token *token, \
const void *ptr, unsigned long off, \
u##bits val) \
{ \
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); \
\
ASSERT(token); \
ASSERT(token->kaddr); \
if (token->offset <= offset && \
(token->offset + PAGE_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(token->eb, offset, size, \
&kaddr, &map_start, &map_len); \
if (err) { \
__le##bits val2; \
\
val2 = cpu_to_le##bits(val); \
write_extent_buffer(token->eb, &val2, offset, size); \
return; \
} \
p = kaddr + part_offset - map_start; \
put_unaligned_le##bits(val, p + off); \
token->kaddr = kaddr; \
token->offset = map_start; \
} \
void btrfs_set_##bits(struct extent_buffer *eb, void *ptr, \
unsigned long off, u##bits val) \
{ \
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); \
\
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); \
}
DEFINE_BTRFS_SETGET_BITS(8)
DEFINE_BTRFS_SETGET_BITS(16)
DEFINE_BTRFS_SETGET_BITS(32)
DEFINE_BTRFS_SETGET_BITS(64)
void btrfs_node_key(const 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);
}