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 #include <asm/unaligned.h>
  21
  22 #include "ctree.h"
  23
  24 static inline u8 get_unaligned_le8(const void *p)
  25 {
  26        return *(u8 *)p;
  27 }
  28
  29 static inline void put_unaligned_le8(u8 val, void *p)
  30 {
  31        *(u8 *)p = val;
  32 }
  33
  34 /*
  35  * this is some deeply nasty code.
  36  *
  37  * The end result is that anyone who #includes ctree.h gets a
  38  * declaration for the btrfs_set_foo functions and btrfs_foo functions,
  39  * which are wappers of btrfs_set_token_#bits functions and
  40  * btrfs_get_token_#bits functions, which are defined in this file.
  41  *
  42  * These setget functions do all the extent_buffer related mapping
  43  * required to efficiently read and write specific fields in the extent
  44  * buffers.  Every pointer to metadata items in btrfs is really just
  45  * an unsigned long offset into the extent buffer which has been
  46  * cast to a specific type.  This gives us all the gcc type checking.
  47  *
  48  * The extent buffer api is used to do the page spanning work required to
  49  * have a metadata blocksize different from the page size.
  50  */
  51
  52 #define DEFINE_BTRFS_SETGET_BITS(bits)                                  \
  53 u##bits btrfs_get_token_##bits(struct extent_buffer *eb, void *ptr,     \
  54                                unsigned long off,                       \
  55                                struct btrfs_map_token *token)           \
  56 {                                                                       \
  57         unsigned long part_offset = (unsigned long)ptr;                 \
  58         unsigned long offset = part_offset + off;                       \
  59         void *p;                                                        \
  60         int err;                                                        \
  61         char *kaddr;                                                    \
  62         unsigned long map_start;                                        \
  63         unsigned long map_len;                                          \
  64         int size = sizeof(u##bits);                                     \
  65         u##bits res;                                                    \
  66                                                                         \
  67         if (token && token->kaddr && token->offset <= offset &&         \
  68             token->eb == eb &&                                          \
  69            (token->offset + PAGE_CACHE_SIZE >= offset + size)) {        \
  70                 kaddr = token->kaddr;                                   \
  71                 p = kaddr + part_offset - token->offset;                \
  72                 res = get_unaligned_le##bits(p + off);                  \
  73                 return res;                                             \
  74         }                                                               \
  75         err = map_private_extent_buffer(eb, offset, size,               \
  76                                         &kaddr, &map_start, &map_len);  \
  77         if (err) {                                                      \
  78                 __le##bits leres;                                       \
  79                                                                         \
  80                 read_extent_buffer(eb, &leres, offset, size);           \
  81                 return le##bits##_to_cpu(leres);                        \
  82         }                                                               \
  83         p = kaddr + part_offset - map_start;                            \
  84         res = get_unaligned_le##bits(p + off);                          \
  85         if (token) {                                                    \
  86                 token->kaddr = kaddr;                                   \
  87                 token->offset = map_start;                              \
  88                 token->eb = eb;                                         \
  89         }                                                               \
  90         return res;                                                     \
  91 }                                                                       \
  92 void btrfs_set_token_##bits(struct extent_buffer *eb,                   \
  93                             void *ptr, unsigned long off, u##bits val,  \
  94                             struct btrfs_map_token *token)              \
  95 {                                                                       \
  96         unsigned long part_offset = (unsigned long)ptr;                 \
  97         unsigned long offset = part_offset + off;                       \
  98         void *p;                                                        \
  99         int err;                                                        \
 100         char *kaddr;                                                    \
 101         unsigned long map_start;                                        \
 102         unsigned long map_len;                                          \
 103         int size = sizeof(u##bits);                                     \
 104                                                                         \
 105         if (token && token->kaddr && token->offset <= offset &&         \
 106             token->eb == eb &&                                          \
 107            (token->offset + PAGE_CACHE_SIZE >= offset + size)) {        \
 108                 kaddr = token->kaddr;                                   \
 109                 p = kaddr + part_offset - token->offset;                \
 110                 put_unaligned_le##bits(val, p + off);                   \
 111                 return;                                                 \
 112         }                                                               \
 113         err = map_private_extent_buffer(eb, offset, size,               \
 114                         &kaddr, &map_start, &map_len);                  \
 115         if (err) {                                                      \
 116                 __le##bits val2;                                        \
 117                                                                         \
 118                 val2 = cpu_to_le##bits(val);                            \
 119                 write_extent_buffer(eb, &val2, offset, size);           \
 120                 return;                                                 \
 121         }                                                               \
 122         p = kaddr + part_offset - map_start;                            \
 123         put_unaligned_le##bits(val, p + off);                           \
 124         if (token) {                                                    \
 125                 token->kaddr = kaddr;                                   \
 126                 token->offset = map_start;                              \
 127                 token->eb = eb;                                         \
 128         }                                                               \
 129 }
 130
 131 DEFINE_BTRFS_SETGET_BITS(8)
 132 DEFINE_BTRFS_SETGET_BITS(16)
 133 DEFINE_BTRFS_SETGET_BITS(32)
 134 DEFINE_BTRFS_SETGET_BITS(64)
 135
 136 void btrfs_node_key(struct extent_buffer *eb,
 137                     struct btrfs_disk_key *disk_key, int nr)
 138 {
 139         unsigned long ptr = btrfs_node_key_ptr_offset(nr);
 140         read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
 141                        struct btrfs_key_ptr, key, disk_key);
 142 }