e2fsprogs/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 extern errcode_t ext2fs_bmap(ext2_filsys fs, ext2_ino_t ino,
  22                              struct ext2_inode *inode,
  23                              char *block_buf, int bmap_flags,
  24                              blk_t block, blk_t *phys_blk);
  25
  26 #define inode_bmap(inode, nr) ((inode)->i_block[(nr)])
  27
  28 static errcode_t block_ind_bmap(ext2_filsys fs, int flags,
  29                                               blk_t ind, char *block_buf,
  30                                               int *blocks_alloc,
  31                                               blk_t nr, blk_t *ret_blk)
  32 {
  33         errcode_t       retval;
  34         blk_t           b;
  35
  36         if (!ind) {
  37                 if (flags & BMAP_SET)
  38                         return EXT2_ET_SET_BMAP_NO_IND;
  39                 *ret_blk = 0;
  40                 return 0;
  41         }
  42         retval = io_channel_read_blk(fs->io, ind, 1, block_buf);
  43         if (retval)
  44                 return retval;
  45
  46         if (flags & BMAP_SET) {
  47                 b = *ret_blk;
  48 #if BB_BIG_ENDIAN
  49                 if ((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
  50                     (fs->flags & EXT2_FLAG_SWAP_BYTES_WRITE))
  51                         b = ext2fs_swab32(b);
  52 #endif
  53                 ((blk_t *) block_buf)[nr] = b;
  54                 return io_channel_write_blk(fs->io, ind, 1, block_buf);
  55         }
  56
  57         b = ((blk_t *) block_buf)[nr];
  58
  59 #if BB_BIG_ENDIAN
  60         if ((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
  61             (fs->flags & EXT2_FLAG_SWAP_BYTES_READ))
  62                 b = ext2fs_swab32(b);
  63 #endif
  64
  65         if (!b && (flags & BMAP_ALLOC)) {
  66                 b = nr ? ((blk_t *) block_buf)[nr-1] : 0;
  67                 retval = ext2fs_alloc_block(fs, b,
  68                                             block_buf + fs->blocksize, &b);
  69                 if (retval)
  70                         return retval;
  71
  72 #if BB_BIG_ENDIAN
  73                 if ((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
  74                     (fs->flags & EXT2_FLAG_SWAP_BYTES_WRITE))
  75                         ((blk_t *) block_buf)[nr] = ext2fs_swab32(b);
  76                 else
  77 #endif
  78                         ((blk_t *) block_buf)[nr] = b;
  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 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 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 #if BB_BIG_ENDIAN
 165                         if ((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
 166                             (fs->flags & EXT2_FLAG_SWAP_BYTES_READ))
 167                                 b = ext2fs_swab32(b);
 168 #endif
 169                         inode_bmap(inode, block) = b;
 170                         inode_dirty++;
 171                         goto done;
 172                 }
 173
 174                 *phys_blk = inode_bmap(inode, block);
 175                 b = block ? inode_bmap(inode, block-1) : 0;
 176
 177                 if ((*phys_blk == 0) && (bmap_flags & BMAP_ALLOC)) {
 178                         retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 179                         if (retval)
 180                                 goto done;
 181                         inode_bmap(inode, block) = b;
 182                         blocks_alloc++;
 183                         *phys_blk = b;
 184                 }
 185                 goto done;
 186         }
 187
 188         /* Indirect block */
 189         block -= EXT2_NDIR_BLOCKS;
 190         if (block < addr_per_block) {
 191                 b = inode_bmap(inode, EXT2_IND_BLOCK);
 192                 if (!b) {
 193                         if (!(bmap_flags & BMAP_ALLOC)) {
 194                                 if (bmap_flags & BMAP_SET)
 195                                         retval = EXT2_ET_SET_BMAP_NO_IND;
 196                                 goto done;
 197                         }
 198
 199                         b = inode_bmap(inode, EXT2_IND_BLOCK-1);
 200                         retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 201                         if (retval)
 202                                 goto done;
 203                         inode_bmap(inode, EXT2_IND_BLOCK) = b;
 204                         blocks_alloc++;
 205                 }
 206                 retval = block_ind_bmap(fs, bmap_flags, b, block_buf,
 207                                         &blocks_alloc, block, phys_blk);
 208                 goto done;
 209         }
 210
 211         /* Doubly indirect block  */
 212         block -= addr_per_block;
 213         if (block < addr_per_block * addr_per_block) {
 214                 b = inode_bmap(inode, EXT2_DIND_BLOCK);
 215                 if (!b) {
 216                         if (!(bmap_flags & BMAP_ALLOC)) {
 217                                 if (bmap_flags & BMAP_SET)
 218                                         retval = EXT2_ET_SET_BMAP_NO_IND;
 219                                 goto done;
 220                         }
 221
 222                         b = inode_bmap(inode, EXT2_IND_BLOCK);
 223                         retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 224                         if (retval)
 225                                 goto done;
 226                         inode_bmap(inode, EXT2_DIND_BLOCK) = b;
 227                         blocks_alloc++;
 228                 }
 229                 retval = block_dind_bmap(fs, bmap_flags, b, block_buf,
 230                                          &blocks_alloc, block, phys_blk);
 231                 goto done;
 232         }
 233
 234         /* Triply indirect block */
 235         block -= addr_per_block * addr_per_block;
 236         b = inode_bmap(inode, EXT2_TIND_BLOCK);
 237         if (!b) {
 238                 if (!(bmap_flags & BMAP_ALLOC)) {
 239                         if (bmap_flags & BMAP_SET)
 240                                 retval = EXT2_ET_SET_BMAP_NO_IND;
 241                         goto done;
 242                 }
 243
 244                 b = inode_bmap(inode, EXT2_DIND_BLOCK);
 245                 retval = ext2fs_alloc_block(fs, b, block_buf, &b);
 246                 if (retval)
 247                         goto done;
 248                 inode_bmap(inode, EXT2_TIND_BLOCK) = b;
 249                 blocks_alloc++;
 250         }
 251         retval = block_tind_bmap(fs, bmap_flags, b, block_buf,
 252                                  &blocks_alloc, block, phys_blk);
 253 done:
 254         ext2fs_free_mem(&buf);
 255         if ((retval == 0) && (blocks_alloc || inode_dirty)) {
 256                 inode->i_blocks += (blocks_alloc * fs->blocksize) / 512;
 257                 retval = ext2fs_write_inode(fs, ino, inode);
 258         }
 259         return retval;
 260 }
 261
 262
 263