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1cbb1f454e
We have reader helpers for most of the on-disk structures that use an extent_buffer and pointer as offset into the buffer that are read-only. We should mark them as const and, in turn, allow consumers of these interfaces to mark the buffers const as well. No impact on code, but serves as documentation that a buffer is intended not to be modified. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
144 lines
4.5 KiB
C
144 lines
4.5 KiB
C
/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#include <linux/highmem.h>
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#include <asm/unaligned.h>
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#include "ctree.h"
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static inline u8 get_unaligned_le8(const void *p)
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{
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return *(u8 *)p;
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}
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static inline void put_unaligned_le8(u8 val, void *p)
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{
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*(u8 *)p = val;
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}
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/*
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* this is some deeply nasty code.
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*
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* The end result is that anyone who #includes ctree.h gets a
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* declaration for the btrfs_set_foo functions and btrfs_foo functions,
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* which are wrappers of btrfs_set_token_#bits functions and
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* btrfs_get_token_#bits functions, which are defined in this file.
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*
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* These setget functions do all the extent_buffer related mapping
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* required to efficiently read and write specific fields in the extent
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* buffers. Every pointer to metadata items in btrfs is really just
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* an unsigned long offset into the extent buffer which has been
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* cast to a specific type. This gives us all the gcc type checking.
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*
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* The extent buffer api is used to do the page spanning work required to
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* have a metadata blocksize different from the page size.
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*/
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#define DEFINE_BTRFS_SETGET_BITS(bits) \
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u##bits btrfs_get_token_##bits(const struct extent_buffer *eb, \
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const void *ptr, unsigned long off, \
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struct btrfs_map_token *token) \
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{ \
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unsigned long part_offset = (unsigned long)ptr; \
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unsigned long offset = part_offset + off; \
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void *p; \
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int err; \
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char *kaddr; \
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unsigned long map_start; \
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unsigned long map_len; \
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int size = sizeof(u##bits); \
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u##bits res; \
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\
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if (token && token->kaddr && token->offset <= offset && \
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token->eb == eb && \
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(token->offset + PAGE_SIZE >= offset + size)) { \
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kaddr = token->kaddr; \
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p = kaddr + part_offset - token->offset; \
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res = get_unaligned_le##bits(p + off); \
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return res; \
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} \
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err = map_private_extent_buffer(eb, offset, size, \
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&kaddr, &map_start, &map_len); \
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if (err) { \
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__le##bits leres; \
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\
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read_extent_buffer(eb, &leres, offset, size); \
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return le##bits##_to_cpu(leres); \
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} \
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p = kaddr + part_offset - map_start; \
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res = get_unaligned_le##bits(p + off); \
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if (token) { \
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token->kaddr = kaddr; \
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token->offset = map_start; \
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token->eb = eb; \
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} \
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return res; \
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} \
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void btrfs_set_token_##bits(struct extent_buffer *eb, \
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const void *ptr, unsigned long off, \
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u##bits val, \
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struct btrfs_map_token *token) \
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{ \
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unsigned long part_offset = (unsigned long)ptr; \
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unsigned long offset = part_offset + off; \
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void *p; \
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int err; \
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char *kaddr; \
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unsigned long map_start; \
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unsigned long map_len; \
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int size = sizeof(u##bits); \
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\
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if (token && token->kaddr && token->offset <= offset && \
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token->eb == eb && \
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(token->offset + PAGE_SIZE >= offset + size)) { \
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kaddr = token->kaddr; \
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p = kaddr + part_offset - token->offset; \
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put_unaligned_le##bits(val, p + off); \
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return; \
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} \
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err = map_private_extent_buffer(eb, offset, size, \
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&kaddr, &map_start, &map_len); \
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if (err) { \
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__le##bits val2; \
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\
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val2 = cpu_to_le##bits(val); \
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write_extent_buffer(eb, &val2, offset, size); \
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return; \
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} \
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p = kaddr + part_offset - map_start; \
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put_unaligned_le##bits(val, p + off); \
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if (token) { \
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token->kaddr = kaddr; \
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token->offset = map_start; \
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token->eb = eb; \
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} \
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}
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DEFINE_BTRFS_SETGET_BITS(8)
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DEFINE_BTRFS_SETGET_BITS(16)
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DEFINE_BTRFS_SETGET_BITS(32)
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DEFINE_BTRFS_SETGET_BITS(64)
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void btrfs_node_key(const struct extent_buffer *eb,
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struct btrfs_disk_key *disk_key, int nr)
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{
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unsigned long ptr = btrfs_node_key_ptr_offset(nr);
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read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
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struct btrfs_key_ptr, key, disk_key);
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}
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