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
  41 #define BTRFS_SETGET_FUNCS(name, type, member, bits)                    \
  42 u##bits btrfs_##name(struct extent_buffer *eb,                          \
  43                                    type *s)                             \
  44 {                                                                       \
  45         unsigned long part_offset = (unsigned long)s;                   \
  46         unsigned long offset = part_offset + offsetof(type, member);    \
  47         type *p;                                                        \
  48         /* ugly, but we want the fast path here */                      \
  49         if (eb->map_token && offset >= eb->map_start &&                 \
  50             offset + sizeof(((type *)0)->member) <= eb->map_start +     \
  51             eb->map_len) {                                              \
  52                 p = (type *)(eb->kaddr + part_offset - eb->map_start);  \
  53                 return le##bits##_to_cpu(p->member);                    \
  54         }                                                               \
  55         {                                                               \
  56                 int err;                                                \
  57                 char *map_token;                                        \
  58                 char *kaddr;                                            \
  59                 int unmap_on_exit = (eb->map_token == NULL);            \
  60                 unsigned long map_start;                                \
  61                 unsigned long map_len;                                  \
  62                 __le##bits res;                                         \
  63                 err = map_extent_buffer(eb, offset,                     \
  64                                 sizeof(((type *)0)->member),            \
  65                                 &map_token, &kaddr,                     \
  66                                 &map_start, &map_len, KM_USER1);        \
  67                 if (err) {                                              \
  68                         read_eb_member(eb, s, type, member, &res);      \
  69                         return le##bits##_to_cpu(res);                  \
  70                 }                                                       \
  71                 p = (type *)(kaddr + part_offset - map_start);          \
  72                 res = le##bits##_to_cpu(p->member);                     \
  73                 if (unmap_on_exit)                                      \
  74                         unmap_extent_buffer(eb, map_token, KM_USER1);   \
  75                 return res;                                             \
  76         }                                                               \
  77 }                                                                       \
  78 void btrfs_set_##name(struct extent_buffer *eb,                         \
  79                                     type *s, u##bits val)               \
  80 {                                                                       \
  81         unsigned long part_offset = (unsigned long)s;                   \
  82         unsigned long offset = part_offset + offsetof(type, member);    \
  83         type *p;                                                        \
  84         /* ugly, but we want the fast path here */                      \
  85         if (eb->map_token && offset >= eb->map_start &&                 \
  86             offset + sizeof(((type *)0)->member) <= eb->map_start +     \
  87             eb->map_len) {                                              \
  88                 p = (type *)(eb->kaddr + part_offset - eb->map_start);  \
  89                 p->member = cpu_to_le##bits(val);                       \
  90                 return;                                                 \
  91         }                                                               \
  92         {                                                               \
  93                 int err;                                                \
  94                 char *map_token;                                        \
  95                 char *kaddr;                                            \
  96                 int unmap_on_exit = (eb->map_token == NULL);            \
  97                 unsigned long map_start;                                \
  98                 unsigned long map_len;                                  \
  99                 err = map_extent_buffer(eb, offset,                     \
 100                                 sizeof(((type *)0)->member),            \
 101                                 &map_token, &kaddr,                     \
 102                                 &map_start, &map_len, KM_USER1);        \
 103                 if (err) {                                              \
 104                         val = cpu_to_le##bits(val);                     \
 105                         write_eb_member(eb, s, type, member, &val);     \
 106                         return;                                         \
 107                 }                                                       \
 108                 p = (type *)(kaddr + part_offset - map_start);          \
 109                 p->member = cpu_to_le##bits(val);                       \
 110                 if (unmap_on_exit)                                      \
 111                         unmap_extent_buffer(eb, map_token, KM_USER1);   \
 112         }                                                               \
 113 }
 114
 115 #include "ctree.h"
 116
 117 void btrfs_node_key(struct extent_buffer *eb,
 118                     struct btrfs_disk_key *disk_key, int nr)
 119 {
 120         unsigned long ptr = btrfs_node_key_ptr_offset(nr);
 121         if (eb->map_token && ptr >= eb->map_start &&
 122             ptr + sizeof(*disk_key) <= eb->map_start + eb->map_len) {
 123                 memcpy(disk_key, eb->kaddr + ptr - eb->map_start,
 124                         sizeof(*disk_key));
 125                 return;
 126         } else if (eb->map_token) {
 127                 unmap_extent_buffer(eb, eb->map_token, KM_USER1);
 128                 eb->map_token = NULL;
 129         }
 130         read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
 131                        struct btrfs_key_ptr, key, disk_key);
 132 }