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 static bool check_setget_bounds(const struct extent_buffer *eb,
  21                                 const void *ptr, unsigned off, int size)
  22 {
  23         const unsigned long member_offset = (unsigned long)ptr + off;
  24
  25         if (member_offset > eb->len) {
  26                 btrfs_warn(eb->fs_info,
  27         "bad eb member start: ptr 0x%lx start %llu member offset %lu size %d",
  28                         (unsigned long)ptr, eb->start, member_offset, size);
  29                 return false;
  30         }
  31         if (member_offset + size > eb->len) {
  32                 btrfs_warn(eb->fs_info,
  33         "bad eb member end: ptr 0x%lx start %llu member offset %lu size %d",
  34                         (unsigned long)ptr, eb->start, member_offset, size);
  35                 return false;
  36         }
  37
  38         return true;
  39 }
  40
  41 /*
  42  * this is some deeply nasty code.
  43  *
  44  * The end result is that anyone who #includes ctree.h gets a
  45  * declaration for the btrfs_set_foo functions and btrfs_foo functions,
  46  * which are wrappers of btrfs_set_token_#bits functions and
  47  * btrfs_get_token_#bits functions, which are defined in this file.
  48  *
  49  * These setget functions do all the extent_buffer related mapping
  50  * required to efficiently read and write specific fields in the extent
  51  * buffers.  Every pointer to metadata items in btrfs is really just
  52  * an unsigned long offset into the extent buffer which has been
  53  * cast to a specific type.  This gives us all the gcc type checking.
  54  *
  55  * The extent buffer api is used to do the page spanning work required to
  56  * have a metadata blocksize different from the page size.
  57  *
  58  * There are 2 variants defined, one with a token pointer and one without.
  59  */
  60
  61 #define DEFINE_BTRFS_SETGET_BITS(bits)                                  \
  62 u##bits btrfs_get_token_##bits(struct btrfs_map_token *token,           \
  63                                const void *ptr, unsigned long off)      \
  64 {                                                                       \
  65         const unsigned long member_offset = (unsigned long)ptr + off;   \
  66         const unsigned long idx = member_offset >> PAGE_SHIFT;          \
  67         const unsigned long oip = offset_in_page(member_offset);        \
  68         const int size = sizeof(u##bits);                               \
  69         __le##bits leres;                                               \
  70                                                                         \
  71         ASSERT(token);                                                  \
  72         ASSERT(token->kaddr);                                           \
  73         ASSERT(check_setget_bounds(token->eb, ptr, off, size));         \
  74         if (token->offset <= member_offset &&                           \
  75             member_offset + size <= token->offset + PAGE_SIZE) {        \
  76                 return get_unaligned_le##bits(token->kaddr + oip);      \
  77         }                                                               \
  78         if (oip + size <= PAGE_SIZE) {                                  \
  79                 token->kaddr = page_address(token->eb->pages[idx]);     \
  80                 token->offset = idx << PAGE_SHIFT;                      \
  81                 return get_unaligned_le##bits(token->kaddr + oip);      \
  82         }                                                               \
  83         token->kaddr = page_address(token->eb->pages[idx + 1]);         \
  84         token->offset = (idx + 1) << PAGE_SHIFT;                        \
  85         read_extent_buffer(token->eb, &leres, member_offset, size);     \
  86         return le##bits##_to_cpu(leres);                                \
  87 }                                                                       \
  88 u##bits btrfs_get_##bits(const struct extent_buffer *eb,                \
  89                          const void *ptr, unsigned long off)            \
  90 {                                                                       \
  91         const unsigned long member_offset = (unsigned long)ptr + off;   \
  92         const unsigned long oip = offset_in_page(member_offset);        \
  93         const int size = sizeof(u##bits);                               \
  94         __le##bits leres;                                               \
  95                                                                         \
  96         ASSERT(check_setget_bounds(eb, ptr, off, size));                \
  97         if (oip + size <= PAGE_SIZE) {                                  \
  98                 const unsigned long idx = member_offset >> PAGE_SHIFT;  \
  99                 const char *kaddr = page_address(eb->pages[idx]);       \
 100                 return get_unaligned_le##bits(kaddr + oip);             \
 101         }                                                               \
 102         read_extent_buffer(eb, &leres, member_offset, size);            \
 103         return le##bits##_to_cpu(leres);                                \
 104 }                                                                       \
 105 void btrfs_set_token_##bits(struct btrfs_map_token *token,              \
 106                             const void *ptr, unsigned long off,         \
 107                             u##bits val)                                \
 108 {                                                                       \
 109         unsigned long part_offset = (unsigned long)ptr;                 \
 110         unsigned long offset = part_offset + off;                       \
 111         void *p;                                                        \
 112         int err;                                                        \
 113         char *kaddr;                                                    \
 114         unsigned long map_start;                                        \
 115         unsigned long map_len;                                          \
 116         int size = sizeof(u##bits);                                     \
 117                                                                         \
 118         ASSERT(token);                                                  \
 119         ASSERT(token->kaddr);                                           \
 120         ASSERT(check_setget_bounds(token->eb, ptr, off, size));         \
 121         if (token->offset <= offset &&                                  \
 122            (token->offset + PAGE_SIZE >= offset + size)) {      \
 123                 kaddr = token->kaddr;                                   \
 124                 p = kaddr + part_offset - token->offset;                \
 125                 put_unaligned_le##bits(val, p + off);                   \
 126                 return;                                                 \
 127         }                                                               \
 128         err = map_private_extent_buffer(token->eb, offset, size,        \
 129                         &kaddr, &map_start, &map_len);                  \
 130         if (err) {                                                      \
 131                 __le##bits val2;                                        \
 132                                                                         \
 133                 val2 = cpu_to_le##bits(val);                            \
 134                 write_extent_buffer(token->eb, &val2, offset, size);    \
 135                 return;                                                 \
 136         }                                                               \
 137         p = kaddr + part_offset - map_start;                            \
 138         put_unaligned_le##bits(val, p + off);                           \
 139         token->kaddr = kaddr;                                           \
 140         token->offset = map_start;                                      \
 141 }                                                                       \
 142 void btrfs_set_##bits(struct extent_buffer *eb, void *ptr,              \
 143                       unsigned long off, u##bits val)                   \
 144 {                                                                       \
 145         unsigned long part_offset = (unsigned long)ptr;                 \
 146         unsigned long offset = part_offset + off;                       \
 147         void *p;                                                        \
 148         int err;                                                        \
 149         char *kaddr;                                                    \
 150         unsigned long map_start;                                        \
 151         unsigned long map_len;                                          \
 152         int size = sizeof(u##bits);                                     \
 153                                                                         \
 154         ASSERT(check_setget_bounds(eb, ptr, off, size));                \
 155         err = map_private_extent_buffer(eb, offset, size,               \
 156                         &kaddr, &map_start, &map_len);                  \
 157         if (err) {                                                      \
 158                 __le##bits val2;                                        \
 159                                                                         \
 160                 val2 = cpu_to_le##bits(val);                            \
 161                 write_extent_buffer(eb, &val2, offset, size);           \
 162                 return;                                                 \
 163         }                                                               \
 164         p = kaddr + part_offset - map_start;                            \
 165         put_unaligned_le##bits(val, p + off);                           \
 166 }
 167
 168 DEFINE_BTRFS_SETGET_BITS(8)
 169 DEFINE_BTRFS_SETGET_BITS(16)
 170 DEFINE_BTRFS_SETGET_BITS(32)
 171 DEFINE_BTRFS_SETGET_BITS(64)
 172
 173 void btrfs_node_key(const struct extent_buffer *eb,
 174                     struct btrfs_disk_key *disk_key, int nr)
 175 {
 176         unsigned long ptr = btrfs_node_key_ptr_offset(nr);
 177         read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
 178                        struct btrfs_key_ptr, key, disk_key);
 179 }