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)                    \
  45 u##bits btrfs_##name(struct extent_buffer *eb, type *s);                \
  46 void btrfs_set_##name(struct extent_buffer *eb, type *s, u##bits val);  \
  47 u##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         int err;                                                \
  54         char *kaddr;                                            \
  55         unsigned long map_start;                                \
  56         unsigned long map_len;                                  \
  57         u##bits res;                                            \
  58         err = map_private_extent_buffer(eb, offset,             \
  59                         sizeof(((type *)0)->member),            \
  60                         &kaddr, &map_start, &map_len);          \
  61         if (err) {                                              \
  62                 __le##bits leres;                               \
  63                 read_eb_member(eb, s, type, member, &leres);    \
  64                 return le##bits##_to_cpu(leres);                \
  65         }                                                       \
  66         p = (type *)(kaddr + part_offset - map_start);          \
  67         res = le##bits##_to_cpu(p->member);                     \
  68         return res;                                             \
  69 }                                                                       \
  70 void btrfs_set_##name(struct extent_buffer *eb,                         \
  71                                     type *s, u##bits val)               \
  72 {                                                                       \
  73         unsigned long part_offset = (unsigned long)s;                   \
  74         unsigned long offset = part_offset + offsetof(type, member);    \
  75         type *p;                                                        \
  76         int err;                                                \
  77         char *kaddr;                                            \
  78         unsigned long map_start;                                \
  79         unsigned long map_len;                                  \
  80         err = map_private_extent_buffer(eb, offset,             \
  81                         sizeof(((type *)0)->member),            \
  82                         &kaddr, &map_start, &map_len);          \
  83         if (err) {                                              \
  84                 __le##bits val2;                                \
  85                 val2 = cpu_to_le##bits(val);                    \
  86                 write_eb_member(eb, s, type, member, &val2);    \
  87                 return;                                         \
  88         }                                                       \
  89         p = (type *)(kaddr + part_offset - map_start);          \
  90         p->member = cpu_to_le##bits(val);                       \
  91 }
  92
  93 #include "ctree.h"
  94
  95 void btrfs_node_key(struct extent_buffer *eb,
  96                     struct btrfs_disk_key *disk_key, int nr)
  97 {
  98         unsigned long ptr = btrfs_node_key_ptr_offset(nr);
  99         read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
 100                        struct btrfs_key_ptr, key, disk_key);
 101 }