fs/btrfs/struct-funcs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2007 Oracle.  All rights reserved.
   4  */
   5
   6 #include <asm/unaligned.h>
   7
   8 #include "ctree.h"
   9
  10 static inline u8 get_unaligned_le8(const void *p)
  11 {
  12        return *(u8 *)p;
  13 }
  14
  15 static inline void put_unaligned_le8(u8 val, void *p)
  16 {
  17        *(u8 *)p = val;
  18 }
  19
  20 /*
  21  * this is some deeply nasty code.
  22  *
  23  * The end result is that anyone who #includes ctree.h gets a
  24  * declaration for the btrfs_set_foo functions and btrfs_foo functions,
  25  * which are wrappers of btrfs_set_token_#bits functions and
  26  * btrfs_get_token_#bits functions, which are defined in this file.
  27  *
  28  * These setget functions do all the extent_buffer related mapping
  29  * required to efficiently read and write specific fields in the extent
  30  * buffers.  Every pointer to metadata items in btrfs is really just
  31  * an unsigned long offset into the extent buffer which has been
  32  * cast to a specific type.  This gives us all the gcc type checking.
  33  *
  34  * The extent buffer api is used to do the page spanning work required to
  35  * have a metadata blocksize different from the page size.
  36  */
  37
  38 #define DEFINE_BTRFS_SETGET_BITS(bits)                                  \
  39 u##bits btrfs_get_token_##bits(const struct extent_buffer *eb,          \
  40                                const void *ptr, unsigned long off,      \
  41                                struct btrfs_map_token *token)           \
  42 {                                                                       \
  43         unsigned long part_offset = (unsigned long)ptr;                 \
  44         unsigned long offset = part_offset + off;                       \
  45         void *p;                                                        \
  46         int err;                                                        \
  47         char *kaddr;                                                    \
  48         unsigned long map_start;                                        \
  49         unsigned long map_len;                                          \
  50         int size = sizeof(u##bits);                                     \
  51         u##bits res;                                                    \
  52                                                                         \
  53         if (token && token->kaddr && token->offset <= offset &&         \
  54             token->eb == eb &&                                          \
  55            (token->offset + PAGE_SIZE >= offset + size)) {      \
  56                 kaddr = token->kaddr;                                   \
  57                 p = kaddr + part_offset - token->offset;                \
  58                 res = get_unaligned_le##bits(p + off);                  \
  59                 return res;                                             \
  60         }                                                               \
  61         err = map_private_extent_buffer(eb, offset, size,               \
  62                                         &kaddr, &map_start, &map_len);  \
  63         if (err) {                                                      \
  64                 __le##bits leres;                                       \
  65                                                                         \
  66                 read_extent_buffer(eb, &leres, offset, size);           \
  67                 return le##bits##_to_cpu(leres);                        \
  68         }                                                               \
  69         p = kaddr + part_offset - map_start;                            \
  70         res = get_unaligned_le##bits(p + off);                          \
  71         if (token) {                                                    \
  72                 token->kaddr = kaddr;                                   \
  73                 token->offset = map_start;                              \
  74                 token->eb = eb;                                         \
  75         }                                                               \
  76         return res;                                                     \
  77 }                                                                       \
  78 void btrfs_set_token_##bits(struct extent_buffer *eb,                   \
  79                             const void *ptr, unsigned long off,         \
  80                             u##bits val,                                \
  81                             struct btrfs_map_token *token)              \
  82 {                                                                       \
  83         unsigned long part_offset = (unsigned long)ptr;                 \
  84         unsigned long offset = part_offset + off;                       \
  85         void *p;                                                        \
  86         int err;                                                        \
  87         char *kaddr;                                                    \
  88         unsigned long map_start;                                        \
  89         unsigned long map_len;                                          \
  90         int size = sizeof(u##bits);                                     \
  91                                                                         \
  92         if (token && token->kaddr && token->offset <= offset &&         \
  93             token->eb == eb &&                                          \
  94            (token->offset + PAGE_SIZE >= offset + size)) {      \
  95                 kaddr = token->kaddr;                                   \
  96                 p = kaddr + part_offset - token->offset;                \
  97                 put_unaligned_le##bits(val, p + off);                   \
  98                 return;                                                 \
  99         }                                                               \
 100         err = map_private_extent_buffer(eb, offset, size,               \
 101                         &kaddr, &map_start, &map_len);                  \
 102         if (err) {                                                      \
 103                 __le##bits val2;                                        \
 104                                                                         \
 105                 val2 = cpu_to_le##bits(val);                            \
 106                 write_extent_buffer(eb, &val2, offset, size);           \
 107                 return;                                                 \
 108         }                                                               \
 109         p = kaddr + part_offset - map_start;                            \
 110         put_unaligned_le##bits(val, p + off);                           \
 111         if (token) {                                                    \
 112                 token->kaddr = kaddr;                                   \
 113                 token->offset = map_start;                              \
 114                 token->eb = eb;                                         \
 115         }                                                               \
 116 }
 117
 118 DEFINE_BTRFS_SETGET_BITS(8)
 119 DEFINE_BTRFS_SETGET_BITS(16)
 120 DEFINE_BTRFS_SETGET_BITS(32)
 121 DEFINE_BTRFS_SETGET_BITS(64)
 122
 123 void btrfs_node_key(const struct extent_buffer *eb,
 124                     struct btrfs_disk_key *disk_key, int nr)
 125 {
 126         unsigned long ptr = btrfs_node_key_ptr_offset(nr);
 127         read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
 128                        struct btrfs_key_ptr, key, disk_key);
 129 }