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 <linux/highmem.h>
   7 #include <asm/unaligned.h>
   8
   9 #include "ctree.h"
  10
  11 static inline u8 get_unaligned_le8(const void *p)
  12 {
  13        return *(u8 *)p;
  14 }
  15
  16 static inline void put_unaligned_le8(u8 val, void *p)
  17 {
  18        *(u8 *)p = val;
  19 }
  20
  21 /*
  22  * this is some deeply nasty code.
  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  * which are wrappers of btrfs_set_token_#bits functions and
  27  * btrfs_get_token_#bits functions, which are defined in this file.
  28  *
  29  * These setget functions do all the extent_buffer related mapping
  30  * required to efficiently read and write specific fields in the extent
  31  * buffers.  Every pointer to metadata items in btrfs is really just
  32  * an unsigned long offset into the extent buffer which has been
  33  * cast to a specific type.  This gives us all the gcc type checking.
  34  *
  35  * The extent buffer api is used to do the page spanning work required to
  36  * have a metadata blocksize different from the page size.
  37  */
  38
  39 #define DEFINE_BTRFS_SETGET_BITS(bits)                                  \
  40 u##bits btrfs_get_token_##bits(const struct extent_buffer *eb,          \
  41                                const void *ptr, unsigned long off,      \
  42                                struct btrfs_map_token *token)           \
  43 {                                                                       \
  44         unsigned long part_offset = (unsigned long)ptr;                 \
  45         unsigned long offset = part_offset + off;                       \
  46         void *p;                                                        \
  47         int err;                                                        \
  48         char *kaddr;                                                    \
  49         unsigned long map_start;                                        \
  50         unsigned long map_len;                                          \
  51         int size = sizeof(u##bits);                                     \
  52         u##bits res;                                                    \
  53                                                                         \
  54         if (token && token->kaddr && token->offset <= offset &&         \
  55             token->eb == eb &&                                          \
  56            (token->offset + PAGE_SIZE >= offset + size)) {      \
  57                 kaddr = token->kaddr;                                   \
  58                 p = kaddr + part_offset - token->offset;                \
  59                 res = get_unaligned_le##bits(p + off);                  \
  60                 return res;                                             \
  61         }                                                               \
  62         err = map_private_extent_buffer(eb, offset, size,               \
  63                                         &kaddr, &map_start, &map_len);  \
  64         if (err) {                                                      \
  65                 __le##bits leres;                                       \
  66                                                                         \
  67                 read_extent_buffer(eb, &leres, offset, size);           \
  68                 return le##bits##_to_cpu(leres);                        \
  69         }                                                               \
  70         p = kaddr + part_offset - map_start;                            \
  71         res = get_unaligned_le##bits(p + off);                          \
  72         if (token) {                                                    \
  73                 token->kaddr = kaddr;                                   \
  74                 token->offset = map_start;                              \
  75                 token->eb = eb;                                         \
  76         }                                                               \
  77         return res;                                                     \
  78 }                                                                       \
  79 void btrfs_set_token_##bits(struct extent_buffer *eb,                   \
  80                             const void *ptr, unsigned long off,         \
  81                             u##bits val,                                \
  82                             struct btrfs_map_token *token)              \
  83 {                                                                       \
  84         unsigned long part_offset = (unsigned long)ptr;                 \
  85         unsigned long offset = part_offset + off;                       \
  86         void *p;                                                        \
  87         int err;                                                        \
  88         char *kaddr;                                                    \
  89         unsigned long map_start;                                        \
  90         unsigned long map_len;                                          \
  91         int size = sizeof(u##bits);                                     \
  92                                                                         \
  93         if (token && token->kaddr && token->offset <= offset &&         \
  94             token->eb == eb &&                                          \
  95            (token->offset + PAGE_SIZE >= offset + size)) {      \
  96                 kaddr = token->kaddr;                                   \
  97                 p = kaddr + part_offset - token->offset;                \
  98                 put_unaligned_le##bits(val, p + off);                   \
  99                 return;                                                 \
 100         }                                                               \
 101         err = map_private_extent_buffer(eb, offset, size,               \
 102                         &kaddr, &map_start, &map_len);                  \
 103         if (err) {                                                      \
 104                 __le##bits val2;                                        \
 105                                                                         \
 106                 val2 = cpu_to_le##bits(val);                            \
 107                 write_extent_buffer(eb, &val2, offset, size);           \
 108                 return;                                                 \
 109         }                                                               \
 110         p = kaddr + part_offset - map_start;                            \
 111         put_unaligned_le##bits(val, p + off);                           \
 112         if (token) {                                                    \
 113                 token->kaddr = kaddr;                                   \
 114                 token->offset = map_start;                              \
 115                 token->eb = eb;                                         \
 116         }                                                               \
 117 }
 118
 119 DEFINE_BTRFS_SETGET_BITS(8)
 120 DEFINE_BTRFS_SETGET_BITS(16)
 121 DEFINE_BTRFS_SETGET_BITS(32)
 122 DEFINE_BTRFS_SETGET_BITS(64)
 123
 124 void btrfs_node_key(const struct extent_buffer *eb,
 125                     struct btrfs_disk_key *disk_key, int nr)
 126 {
 127         unsigned long ptr = btrfs_node_key_ptr_offset(nr);
 128         read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
 129                        struct btrfs_key_ptr, key, disk_key);
 130 }