lib/ext2fs/rw_bitmaps.c

   1 /*
   2  * rw_bitmaps.c --- routines to read and write the  inode and block bitmaps.
   3  *
   4  * Copyright (C) 1993, 1994, 1994, 1996 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 #include <stdlib.h>
  18 #include <fcntl.h>
  19 #include <time.h>
  20 #include <sys/stat.h>
  21 #include <sys/types.h>
  22 #if HAVE_ERRNO_H
  23 #include <errno.h>
  24 #endif
  25
  26 #include <linux/ext2_fs.h>
  27
  28 #include "ext2fs.h"
  29
  30 #ifdef __powerpc__
  31 /*
  32  * On the PowerPC, the big-endian variant of the ext2 filesystem
  33  * has its bitmaps stored as 32-bit words with bit 0 as the LSB
  34  * of each word.  Thus a bitmap with only bit 0 set would be, as
  35  * a string of bytes, 00 00 00 01 00 ...
  36  * To cope with this, we byte-reverse each word of a bitmap if
  37  * we have a big-endian filesystem, that is, if we are *not*
  38  * byte-swapping other word-sized numbers.
  39  */
  40 #define EXT2_BIG_ENDIAN_BITMAPS
  41 #endif
  42
  43 #ifdef EXT2_BIG_ENDIAN_BITMAPS
  44 void ext2fs_swap_bitmap(ext2_filsys fs, char *bitmap, int nbytes)
  45 {
  46         __u32 *p = (__u32 *) bitmap;
  47         int n;
  48
  49         for (n = nbytes / sizeof(__u32); n > 0; --n, ++p)
  50                 *p = ext2fs_swab32(*p);
  51 }
  52 #endif
  53
  54 errcode_t ext2fs_write_inode_bitmap(ext2_filsys fs)
  55 {
  56         int             i;
  57         size_t          nbytes;
  58         errcode_t       retval;
  59         char * inode_bitmap = fs->inode_map->bitmap;
  60         char * bitmap_block = NULL;
  61         blk_t           blk;
  62
  63         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
  64
  65         if (!(fs->flags & EXT2_FLAG_RW))
  66                 return EXT2_ET_RO_FILSYS;
  67         if (!inode_bitmap)
  68                 return 0;
  69         nbytes = (size_t) ((EXT2_INODES_PER_GROUP(fs->super)+7) / 8);
  70
  71         bitmap_block = malloc(fs->blocksize);
  72         if (!bitmap_block)
  73                 return ENOMEM;
  74         memset(bitmap_block, 0xff, fs->blocksize);
  75         for (i = 0; i < fs->group_desc_count; i++) {
  76                 memcpy(bitmap_block, inode_bitmap, nbytes);
  77                 blk = fs->group_desc[i].bg_inode_bitmap;
  78                 if (blk) {
  79 #ifdef EXT2_BIG_ENDIAN_BITMAPS
  80                         if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
  81                               (fs->flags & EXT2_FLAG_SWAP_BYTES_WRITE)))
  82                                 ext2fs_swap_bitmap(fs, bitmap_block, nbytes);
  83 #endif
  84                         retval = io_channel_write_blk(fs->io, blk, 1,
  85                                                       bitmap_block);
  86                         if (retval)
  87                                 return EXT2_ET_INODE_BITMAP_WRITE;
  88                 }
  89                 inode_bitmap += nbytes;
  90         }
  91         fs->flags |= EXT2_FLAG_CHANGED;
  92         fs->flags &= ~EXT2_FLAG_IB_DIRTY;
  93         free(bitmap_block);
  94         return 0;
  95 }
  96
  97 errcode_t ext2fs_write_block_bitmap (ext2_filsys fs)
  98 {
  99         int             i;
 100         int             j;
 101         int             nbytes;
 102         int             nbits;
 103         errcode_t       retval;
 104         char * block_bitmap = fs->block_map->bitmap;
 105         char * bitmap_block = NULL;
 106         blk_t           blk;
 107
 108         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 109
 110         if (!(fs->flags & EXT2_FLAG_RW))
 111                 return EXT2_ET_RO_FILSYS;
 112         if (!block_bitmap)
 113                 return 0;
 114         nbytes = EXT2_BLOCKS_PER_GROUP(fs->super) / 8;
 115         bitmap_block = malloc(fs->blocksize);
 116         if (!bitmap_block)
 117                 return ENOMEM;
 118         memset(bitmap_block, 0xff, fs->blocksize);
 119         for (i = 0; i < fs->group_desc_count; i++) {
 120                 memcpy(bitmap_block, block_bitmap, nbytes);
 121                 if (i == fs->group_desc_count - 1) {
 122                         /* Force bitmap padding for the last group */
 123                         nbits = (int) ((fs->super->s_blocks_count
 124                                         - fs->super->s_first_data_block)
 125                                        % EXT2_BLOCKS_PER_GROUP(fs->super));
 126                         if (nbits)
 127                                 for (j = nbits; j < fs->blocksize * 8; j++)
 128                                         ext2fs_set_bit(j, bitmap_block);
 129                 }
 130                 blk = fs->group_desc[i].bg_block_bitmap;
 131                 if (blk) {
 132 #ifdef EXT2_BIG_ENDIAN_BITMAPS
 133                         if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
 134                               (fs->flags & EXT2_FLAG_SWAP_BYTES_WRITE)))
 135                                 ext2fs_swap_bitmap(fs, bitmap_block, nbytes);
 136 #endif
 137                         retval = io_channel_write_blk(fs->io, blk, 1,
 138                                                       bitmap_block);
 139                         if (retval)
 140                                 return EXT2_ET_BLOCK_BITMAP_WRITE;
 141                 }
 142                 block_bitmap += nbytes;
 143         }
 144         fs->flags |= EXT2_FLAG_CHANGED;
 145         fs->flags &= ~EXT2_FLAG_BB_DIRTY;
 146         free(bitmap_block);
 147         return 0;
 148 }
 149
 150 static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
 151 {
 152         int i;
 153         char *block_bitmap = 0, *inode_bitmap = 0;
 154         char *buf;
 155         errcode_t retval;
 156         int block_nbytes = (int) EXT2_BLOCKS_PER_GROUP(fs->super) / 8;
 157         int inode_nbytes = (int) EXT2_INODES_PER_GROUP(fs->super) / 8;
 158         blk_t   blk;
 159
 160         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 161
 162         fs->write_bitmaps = ext2fs_write_bitmaps;
 163
 164         buf = malloc(strlen(fs->device_name) + 80);
 165         if (do_block) {
 166                 if (fs->block_map)
 167                         ext2fs_free_block_bitmap(fs->block_map);
 168                 sprintf(buf, "block bitmap for %s", fs->device_name);
 169                 retval = ext2fs_allocate_block_bitmap(fs, buf, &fs->block_map);
 170                 if (retval)
 171                         goto cleanup;
 172                 block_bitmap = fs->block_map->bitmap;
 173         }
 174         if (do_inode) {
 175                 if (fs->inode_map)
 176                         ext2fs_free_inode_bitmap(fs->inode_map);
 177                 sprintf(buf, "inode bitmap for %s", fs->device_name);
 178                 retval = ext2fs_allocate_inode_bitmap(fs, buf, &fs->inode_map);
 179                 if (retval)
 180                         goto cleanup;
 181                 inode_bitmap = fs->inode_map->bitmap;
 182         }
 183         free(buf);
 184
 185         for (i = 0; i < fs->group_desc_count; i++) {
 186                 if (block_bitmap) {
 187                         blk = fs->group_desc[i].bg_block_bitmap;
 188                         if (blk) {
 189                                 retval = io_channel_read_blk(fs->io, blk,
 190                                              -block_nbytes, block_bitmap);
 191                                 if (retval) {
 192                                         retval = EXT2_ET_BLOCK_BITMAP_READ;
 193                                         goto cleanup;
 194                                 }
 195 #ifdef EXT2_BIG_ENDIAN_BITMAPS
 196                                 if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
 197                                       (fs->flags & EXT2_FLAG_SWAP_BYTES_READ)))
 198                                         ext2fs_swap_bitmap(fs, block_bitmap, block_nbytes);
 199 #endif
 200                         } else
 201                                 memset(block_bitmap, 0, block_nbytes);
 202                         block_bitmap += block_nbytes;
 203                 }
 204                 if (inode_bitmap) {
 205                         blk = fs->group_desc[i].bg_inode_bitmap;
 206                         if (blk) {
 207                                 retval = io_channel_read_blk(fs->io, blk,
 208                                              -inode_nbytes, inode_bitmap);
 209                                 if (retval) {
 210                                         retval = EXT2_ET_INODE_BITMAP_READ;
 211                                         goto cleanup;
 212                                 }
 213 #ifdef EXT2_BIG_ENDIAN_BITMAPS
 214                                 if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
 215                                       (fs->flags & EXT2_FLAG_SWAP_BYTES_READ)))
 216                                         ext2fs_swap_bitmap(fs, inode_bitmap, inode_nbytes);
 217 #endif
 218                         } else
 219                                 memset(inode_bitmap, 0, inode_nbytes);
 220                         inode_bitmap += inode_nbytes;
 221                 }
 222         }
 223         return 0;
 224
 225 cleanup:
 226         if (do_block) {
 227                 free(fs->block_map);
 228                 fs->block_map = 0;
 229         }
 230         if (do_inode) {
 231                 free(fs->inode_map);
 232                 fs->inode_map = 0;
 233         }
 234         if (buf)
 235                 free(buf);
 236         return retval;
 237 }
 238
 239 errcode_t ext2fs_read_inode_bitmap (ext2_filsys fs)
 240 {
 241         return read_bitmaps(fs, 1, 0);
 242 }
 243
 244 errcode_t ext2fs_read_block_bitmap(ext2_filsys fs)
 245 {
 246         return read_bitmaps(fs, 0, 1);
 247 }
 248
 249 errcode_t ext2fs_read_bitmaps(ext2_filsys fs)
 250 {
 251
 252         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 253
 254         return read_bitmaps(fs, !fs->inode_map, !fs->block_map);
 255 }
 256
 257 errcode_t ext2fs_write_bitmaps(ext2_filsys fs)
 258 {
 259         errcode_t       retval;
 260
 261         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 262
 263         if (fs->block_map && ext2fs_test_bb_dirty(fs)) {
 264                 retval = ext2fs_write_block_bitmap(fs);
 265                 if (retval)
 266                         return retval;
 267         }
 268         if (fs->inode_map && ext2fs_test_ib_dirty(fs)) {
 269                 retval = ext2fs_write_inode_bitmap(fs);
 270                 if (retval)
 271                         return retval;
 272         }
 273         return 0;
 274 }
 275