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rw_bitmaps.c

/*
 * rw_bitmaps.c --- routines to read and write the  inode and block bitmaps.
 *
 * Copyright (C) 1993, 1994, 1994, 1996 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <fcntl.h>
#include <time.h>
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#include "ext2_fs.h"
#include "ext2fs.h"
#include "e2image.h"

#if defined(__powerpc__) && defined(EXT2FS_ENABLE_SWAPFS)
/*
 * On the PowerPC, the big-endian variant of the ext2 filesystem
 * has its bitmaps stored as 32-bit words with bit 0 as the LSB
 * of each word.  Thus a bitmap with only bit 0 set would be, as
 * a string of bytes, 00 00 00 01 00 ...
 * To cope with this, we byte-reverse each word of a bitmap if
 * we have a big-endian filesystem, that is, if we are *not*
 * byte-swapping other word-sized numbers.
 */
#define EXT2_BIG_ENDIAN_BITMAPS
#endif

#ifdef EXT2_BIG_ENDIAN_BITMAPS
void ext2fs_swap_bitmap(ext2_filsys fs, char *bitmap, int nbytes)
{
      __u32 *p = (__u32 *) bitmap;
      int n;
            
      for (n = nbytes / sizeof(__u32); n > 0; --n, ++p)
            *p = ext2fs_swab32(*p);
}
#endif

errcode_t ext2fs_write_inode_bitmap(ext2_filsys fs)
{
      dgrp_t            i;
      size_t            nbytes;
      errcode_t   retval;
      char * inode_bitmap = fs->inode_map->bitmap;
      char * bitmap_block = NULL;
      blk_t       blk;

      EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

      if (!(fs->flags & EXT2_FLAG_RW))
            return EXT2_ET_RO_FILSYS;
      if (!inode_bitmap)
            return 0;
      nbytes = (size_t) ((EXT2_INODES_PER_GROUP(fs->super)+7) / 8);
      
      retval = ext2fs_get_mem(fs->blocksize, (void **) &bitmap_block);
      if (retval)
            return retval;
      memset(bitmap_block, 0xff, fs->blocksize);
      for (i = 0; i < fs->group_desc_count; i++) {
            memcpy(bitmap_block, inode_bitmap, nbytes);
            blk = fs->group_desc[i].bg_inode_bitmap;
            if (blk) {
#ifdef EXT2_BIG_ENDIAN_BITMAPS
                  if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
                        (fs->flags & EXT2_FLAG_SWAP_BYTES_WRITE)))
                        ext2fs_swap_bitmap(fs, bitmap_block, nbytes);
#endif
                  retval = io_channel_write_blk(fs->io, blk, 1,
                                          bitmap_block);
                  if (retval)
                        return EXT2_ET_INODE_BITMAP_WRITE;
            }
            inode_bitmap += nbytes;
      }
      fs->flags |= EXT2_FLAG_CHANGED;
      fs->flags &= ~EXT2_FLAG_IB_DIRTY;
      ext2fs_free_mem((void **) &bitmap_block);
      return 0;
}

errcode_t ext2fs_write_block_bitmap (ext2_filsys fs)
{
      dgrp_t            i;
      int         j;
      int         nbytes;
      int         nbits;
      errcode_t   retval;
      char * block_bitmap = fs->block_map->bitmap;
      char * bitmap_block = NULL;
      blk_t       blk;

      EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

      if (!(fs->flags & EXT2_FLAG_RW))
            return EXT2_ET_RO_FILSYS;
      if (!block_bitmap)
            return 0;
      nbytes = EXT2_BLOCKS_PER_GROUP(fs->super) / 8;
      retval = ext2fs_get_mem(fs->blocksize, (void **) &bitmap_block);
      if (retval)
            return retval;
      memset(bitmap_block, 0xff, fs->blocksize);
      for (i = 0; i < fs->group_desc_count; i++) {
            memcpy(bitmap_block, block_bitmap, nbytes);
            if (i == fs->group_desc_count - 1) {
                  /* Force bitmap padding for the last group */
                  nbits = (int) ((fs->super->s_blocks_count
                              - fs->super->s_first_data_block)
                               % EXT2_BLOCKS_PER_GROUP(fs->super));
                  if (nbits)
                        for (j = nbits; j < fs->blocksize * 8; j++)
                              ext2fs_set_bit(j, bitmap_block);
            }
            blk = fs->group_desc[i].bg_block_bitmap;
            if (blk) {
#ifdef EXT2_BIG_ENDIAN_BITMAPS
                  if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
                        (fs->flags & EXT2_FLAG_SWAP_BYTES_WRITE)))
                        ext2fs_swap_bitmap(fs, bitmap_block, nbytes);
#endif
                  retval = io_channel_write_blk(fs->io, blk, 1,
                                          bitmap_block);
                  if (retval)
                        return EXT2_ET_BLOCK_BITMAP_WRITE;
            }
            block_bitmap += nbytes;
      }
      fs->flags |= EXT2_FLAG_CHANGED;
      fs->flags &= ~EXT2_FLAG_BB_DIRTY;
      ext2fs_free_mem((void **) &bitmap_block);
      return 0;
}

static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
{
      dgrp_t i;
      char *block_bitmap = 0, *inode_bitmap = 0;
      char *buf;
      errcode_t retval;
      int block_nbytes = (int) EXT2_BLOCKS_PER_GROUP(fs->super) / 8;
      int inode_nbytes = (int) EXT2_INODES_PER_GROUP(fs->super) / 8;
      blk_t blk;

      EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

      fs->write_bitmaps = ext2fs_write_bitmaps;

      retval = ext2fs_get_mem(strlen(fs->device_name) + 80, (void **) &buf);
      if (retval)
            return retval;
      if (do_block) {
            if (fs->block_map)
                  ext2fs_free_block_bitmap(fs->block_map);
            sprintf(buf, "block bitmap for %s", fs->device_name);
            retval = ext2fs_allocate_block_bitmap(fs, buf, &fs->block_map);
            if (retval)
                  goto cleanup;
            block_bitmap = fs->block_map->bitmap;
      }
      if (do_inode) {
            if (fs->inode_map)
                  ext2fs_free_inode_bitmap(fs->inode_map);
            sprintf(buf, "inode bitmap for %s", fs->device_name);
            retval = ext2fs_allocate_inode_bitmap(fs, buf, &fs->inode_map);
            if (retval)
                  goto cleanup;
            inode_bitmap = fs->inode_map->bitmap;
      }
      ext2fs_free_mem((void **) &buf);

      if (fs->flags & EXT2_FLAG_IMAGE_FILE) {
            if (inode_bitmap) {
                  blk = (fs->image_header->offset_inodemap /
                         fs->blocksize);
                  retval = io_channel_read_blk(fs->io, blk,
                       -(inode_nbytes * fs->group_desc_count),
                       inode_bitmap);
                  if (retval)
                        goto cleanup;
            }
            if (block_bitmap) {
                  blk = (fs->image_header->offset_blockmap /
                         fs->blocksize);
                  retval = io_channel_read_blk(fs->io, blk, 
                       -(block_nbytes * fs->group_desc_count),
                       block_bitmap);
                  if (retval)
                        goto cleanup;
            }
            return 0;
      }

      for (i = 0; i < fs->group_desc_count; i++) {
            if (block_bitmap) {
                  blk = fs->group_desc[i].bg_block_bitmap;
                  if (blk) {
                        retval = io_channel_read_blk(fs->io, blk,
                                   -block_nbytes, block_bitmap);
                        if (retval) {
                              retval = EXT2_ET_BLOCK_BITMAP_READ;
                              goto cleanup;
                        }
#ifdef EXT2_BIG_ENDIAN_BITMAPS
                        if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
                              (fs->flags & EXT2_FLAG_SWAP_BYTES_READ)))
                              ext2fs_swap_bitmap(fs, block_bitmap, block_nbytes);
#endif
                  } else
                        memset(block_bitmap, 0, block_nbytes);
                  block_bitmap += block_nbytes;
            }
            if (inode_bitmap) {
                  blk = fs->group_desc[i].bg_inode_bitmap;
                  if (blk) {
                        retval = io_channel_read_blk(fs->io, blk,
                                   -inode_nbytes, inode_bitmap);
                        if (retval) {
                              retval = EXT2_ET_INODE_BITMAP_READ;
                              goto cleanup;
                        }
#ifdef EXT2_BIG_ENDIAN_BITMAPS
                        if (!((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
                              (fs->flags & EXT2_FLAG_SWAP_BYTES_READ)))
                              ext2fs_swap_bitmap(fs, inode_bitmap, inode_nbytes);
#endif
                  } else
                        memset(inode_bitmap, 0, inode_nbytes);
                  inode_bitmap += inode_nbytes;
            }
      }
      return 0;
      
cleanup:
      if (do_block) {
            ext2fs_free_mem((void **) &fs->block_map);
            fs->block_map = 0;
      }
      if (do_inode) {
            ext2fs_free_mem((void **) &fs->inode_map);
            fs->inode_map = 0;
      }
      if (buf)
            ext2fs_free_mem((void **) &buf);
      return retval;
}

errcode_t ext2fs_read_inode_bitmap (ext2_filsys fs)
{
      return read_bitmaps(fs, 1, 0);
}

errcode_t ext2fs_read_block_bitmap(ext2_filsys fs)
{
      return read_bitmaps(fs, 0, 1);
}

errcode_t ext2fs_read_bitmaps(ext2_filsys fs)
{

      EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

      if (fs->inode_map && fs->block_map)
            return 0;

      return read_bitmaps(fs, !fs->inode_map, !fs->block_map);
}

errcode_t ext2fs_write_bitmaps(ext2_filsys fs)
{
      errcode_t   retval;

      EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

      if (fs->block_map && ext2fs_test_bb_dirty(fs)) {
            retval = ext2fs_write_block_bitmap(fs);
            if (retval)
                  return retval;
      }
      if (fs->inode_map && ext2fs_test_ib_dirty(fs)) {
            retval = ext2fs_write_inode_bitmap(fs);
            if (retval)
                  return retval;
      }
      return 0;
}     


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