lib/ext2fs/bmap.c

   1 /*
   2  * bmap.c --- logical to physical block mapping
   3  *
   4  * Copyright (C) 1997 Theodore Ts'o.
   5  *
   6  * %Begin-Header%
   7  * This file may be redistributed under the terms of the GNU Public
   8  * License.
   9  * %End-Header%
  10  */
  11
  12 #include <stdio.h>
  13 #include <string.h>
  14 #if HAVE_UNISTD_H
  15 #include <unistd.h>
  16 #endif
  17
  18 #include "ext2_fs.h"
  19 #include "ext2fs.h"
  20
  21 #if defined(__GNUC__) && !defined(NO_INLINE_FUNCS)
  22 #define _BMAP_INLINE_   __inline__
  23 #else
  24 #define _BMAP_INLINE_
  25 #endif
  26
  27 extern errcode_t ext2fs_bmap(ext2_filsys fs, ext2_ino_t ino,
  28                              struct ext2_inode *inode,
  29                              char *block_buf, int bmap_flags,
  30                              blk_t block, blk_t *phys_blk);
  31
  32 #define inode_bmap(inode, nr) ((inode)->i_block[(nr)])
  33
  34 static _BMAP_INLINE_ errcode_t block_ind_bmap(ext2_filsys fs, int flags,
  35                                               blk_t ind, char *block_buf,
  36                                               int *blocks_alloc,
  37                                               blk_t nr, blk_t *ret_blk)
  38 {
  39         errcode_t       retval;
  40         blk_t           b;
  41
  42         if (!ind) {
  43                 if (flags & BMAP_SET)
  44                         return EXT2_ET_SET_BMAP_NO_IND;
  45                 *ret_blk = 0;
  46                 return 0;
  47         }
  48         retval = io_channel_read_blk(fs->io, ind, 1, block_buf);
  49         if (retval)
  50                 return retval;
  51
  52         if (flags & BMAP_SET) {
  53                 b = *ret_blk;
  54 #ifdef WORDS_BIGENDIAN
  55                 b = ext2fs_swab32(b);
  56 #endif
  57                 ((blk_t *) block_buf)[nr] = b;
  58                 return io_channel_write_blk(fs->io, ind, 1, block_buf);
  59         }
  60
  61         b = ((blk_t *) block_buf)[nr];
  62
  63 #ifdef WORDS_BIGENDIAN
  64         b = ext2fs_swab32(b);
  65 #endif
  66
  67         if (!b && (flags & BMAP_ALLOC)) {
  68                 b = nr ? ((blk_t *) block_buf)[nr-1] : 0;
  69                 retval = ext2fs_alloc_block(fs, b,
  70                                             block_buf + fs->blocksize, &b);
  71                 if (retval)
  72                         return retval;
  73
  74 #ifdef WORDS_BIGENDIAN
  75                 ((blk_t *) block_buf)[nr] = ext2fs_swab32(b);
  76 #else
  77                 ((blk_t *) block_buf)[nr] = b;
  78 #endif
  79
  80                 retval = io_channel_write_blk(fs->io, ind, 1, block_buf);
  81                 if (retval)
  82                         return retval;
  83
  84                 (*blocks_alloc)++;
  85         }
  86
  87         *ret_blk = b;
  88         return 0;
  89 }
  90
  91 static _BMAP_INLINE_ errcode_t block_dind_bmap(ext2_filsys fs, int flags,
  92                                                blk_t dind, char *block_buf,
  93                                                int *blocks_alloc,
  94                                                blk_t nr, blk_t *ret_blk)
  95 {
  96         blk_t           b;
  97         errcode_t       retval;
  98         blk_t           addr_per_block;
  99
 100         addr_per_block = (blk_t) fs->blocksize >> 2;
 101
 102         retval = block_ind_bmap(fs, flags & ~BMAP_SET, dind, block_buf,
 103                                 blocks_alloc, nr / addr_per_block, &b);
 104         if (retval)
 105                 return retval;
 106         retval = block_ind_bmap(fs, flags, b, block_buf, blocks_alloc,
 107                                 nr % addr_per_block, ret_blk);
 108         return retval;
 109 }
 110
 111 static _BMAP_INLINE_ errcode_t block_tind_bmap(ext2_filsys fs, int flags,
 112                                                blk_t tind, char *block_buf,
 113                                                int *blocks_alloc,
 114                                                blk_t nr, blk_t *ret_blk)
 115 {
 116         blk_t           b;
 117         errcode_t       retval;
 118         blk_t           addr_per_block;
 119
 120         addr_per_block = (blk_t) fs->blocksize >> 2;
 121
 122         retval = block_dind_bmap(fs, flags & ~BMAP_SET, tind, block_buf,
 123                                  blocks_alloc, nr / addr_per_block, &b);
 124         if (retval)
 125                 return retval;
 126         retval = block_ind_bmap(fs, flags, b, block_buf, blocks_alloc,
 127                                 nr % addr_per_block, ret_blk);
 128         return retval;
 129 }
 130
 131 errcode_t ext2fs_bmap(ext2_filsys fs, ext2_ino_t ino, struct ext2_inode *inode,
 132                       char *block_buf, int bmap_flags, blk_t block,
 133                       blk_t *phys_blk)
 134 {
 135         struct ext2_inode inode_buf;
 136         blk_t addr_per_block;
 137         blk_t   b;
 138         char    *buf = 0;
 139         errcode_t       retval = 0;
 140         int             blocks_alloc = 0, inode_dirty = 0;
 141
 142         if (!(bmap_flags & BMAP_SET))
 143                 *phys_blk = 0;
 144
 145         /* Read inode structure if necessary */
 146         if (!inode) {
 147                 retval = ext2fs_read_inode(fs, ino, &inode_buf);
 148                 if (retval)
 149                         return retval;
 150                 inode = &inode_buf;
 151         }
 152         addr_per_block = (blk_t) fs->blocksize >> 2;
 153
 154         if (!block_buf) {
 155                 retval = ext2fs_get_mem(fs->blocksize * 2, &buf);
 156                 if (retval)
 157                         return retval;
 158                 block_buf = buf;
 159         }
 160
 161         if (block < EXT2_NDIR_BLOCKS) {
 162                 if (bmap_flags & BMAP_SET) {
 163                         b = *phys_blk;
 164 #ifdef WORDS_BIGENDIAN
 165                         b = ext2fs_swab32(b);
 166 #endif
 167                         inode_bmap(inode, block) = b;
 168                         inode_dirty++;
 169                         goto done;
 170                 }
 171
 172                 *phys_blk = inode_bmap(inode, block);
 173                 b = block ? inode_bmap(inode, block-1) : 0;
 174
 175                 if ((*phys_blk == 0) && (bmap_flags & BMAP_ALLOC)) {
 176                         retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 177                         if (retval)
 178                                 goto done;
 179                         inode_bmap(inode, block) = b;
 180                         blocks_alloc++;
 181                         *phys_blk = b;
 182                 }
 183                 goto done;
 184         }
 185
 186         /* Indirect block */
 187         block -= EXT2_NDIR_BLOCKS;
 188         if (block < addr_per_block) {
 189                 b = inode_bmap(inode, EXT2_IND_BLOCK);
 190                 if (!b) {
 191                         if (!(bmap_flags & BMAP_ALLOC)) {
 192                                 if (bmap_flags & BMAP_SET)
 193                                         retval = EXT2_ET_SET_BMAP_NO_IND;
 194                                 goto done;
 195                         }
 196
 197                         b = inode_bmap(inode, EXT2_IND_BLOCK-1);
 198                         retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 199                         if (retval)
 200                                 goto done;
 201                         inode_bmap(inode, EXT2_IND_BLOCK) = b;
 202                         blocks_alloc++;
 203                 }
 204                 retval = block_ind_bmap(fs, bmap_flags, b, block_buf,
 205                                         &blocks_alloc, block, phys_blk);
 206                 goto done;
 207         }
 208
 209         /* Doubly indirect block  */
 210         block -= addr_per_block;
 211         if (block < addr_per_block * addr_per_block) {
 212                 b = inode_bmap(inode, EXT2_DIND_BLOCK);
 213                 if (!b) {
 214                         if (!(bmap_flags & BMAP_ALLOC)) {
 215                                 if (bmap_flags & BMAP_SET)
 216                                         retval = EXT2_ET_SET_BMAP_NO_IND;
 217                                 goto done;
 218                         }
 219
 220                         b = inode_bmap(inode, EXT2_IND_BLOCK);
 221                         retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 222                         if (retval)
 223                                 goto done;
 224                         inode_bmap(inode, EXT2_DIND_BLOCK) = b;
 225                         blocks_alloc++;
 226                 }
 227                 retval = block_dind_bmap(fs, bmap_flags, b, block_buf,
 228                                          &blocks_alloc, block, phys_blk);
 229                 goto done;
 230         }
 231
 232         /* Triply indirect block */
 233         block -= addr_per_block * addr_per_block;
 234         b = inode_bmap(inode, EXT2_TIND_BLOCK);
 235         if (!b) {
 236                 if (!(bmap_flags & BMAP_ALLOC)) {
 237                         if (bmap_flags & BMAP_SET)
 238                                 retval = EXT2_ET_SET_BMAP_NO_IND;
 239                         goto done;
 240                 }
 241
 242                 b = inode_bmap(inode, EXT2_DIND_BLOCK);
 243                 retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 244                 if (retval)
 245                         goto done;
 246                 inode_bmap(inode, EXT2_TIND_BLOCK) = b;
 247                 blocks_alloc++;
 248         }
 249         retval = block_tind_bmap(fs, bmap_flags, b, block_buf,
 250                                  &blocks_alloc, block, phys_blk);
 251 done:
 252         if (buf)
 253                 ext2fs_free_mem(&buf);
 254         if ((retval == 0) && (blocks_alloc || inode_dirty)) {
 255                 inode->i_blocks += (blocks_alloc * fs->blocksize) / 512;
 256                 retval = ext2fs_write_inode(fs, ino, inode);
 257         }
 258         return retval;
 259 }
 260
 261
 262