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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
static 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

static errcode_t write_bitmaps(ext2_filsys fs, int do_inode, int do_block)
{
      dgrp_t            i;
      unsigned int      j;
      int         block_nbytes, inode_nbytes;
      unsigned int      nbits;
      errcode_t   retval;
      char        *block_bitmap, *inode_bitmap;
      char        *block_buf, *inode_buf;
      int         lazy_flag = 0;
      blk_t       blk;

      EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

      if (!(fs->flags & EXT2_FLAG_RW))
            return EXT2_ET_RO_FILSYS;
      if (EXT2_HAS_COMPAT_FEATURE(fs->super, 
                            EXT2_FEATURE_COMPAT_LAZY_BG))
            lazy_flag = 1;
      inode_nbytes = block_nbytes = 0;
      block_bitmap = inode_bitmap = 0;
      if (do_block) {
            block_bitmap = fs->block_map->bitmap;
            block_nbytes = EXT2_BLOCKS_PER_GROUP(fs->super) / 8;
            retval = ext2fs_get_mem(fs->blocksize, &block_buf);
            if (retval)
                  return retval;
            memset(block_buf, 0xff, fs->blocksize);
      }
      if (do_inode) {
            inode_bitmap = fs->inode_map->bitmap;
            inode_nbytes = (size_t) 
                  ((EXT2_INODES_PER_GROUP(fs->super)+7) / 8);
            retval = ext2fs_get_mem(fs->blocksize, &inode_buf);
            if (retval)
                  return retval;
            memset(inode_buf, 0xff, fs->blocksize);
      }

      for (i = 0; i < fs->group_desc_count; i++) {
            if (!block_bitmap || !do_block)
                  goto skip_block_bitmap;

            if (lazy_flag && fs->group_desc[i].bg_flags &
                EXT2_BG_BLOCK_UNINIT) 
                  goto skip_this_block_bitmap;
 
            memcpy(block_buf, block_bitmap, block_nbytes);
            if (i == fs->group_desc_count - 1) {
                  /* Force bitmap padding for the last group */
                  nbits = ((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, block_buf);
            }
            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, block_buf, 
                                       block_nbytes);
#endif
                  retval = io_channel_write_blk(fs->io, blk, 1,
                                          block_buf);
                  if (retval)
                        return EXT2_ET_BLOCK_BITMAP_WRITE;
            }
      skip_this_block_bitmap:
            block_bitmap += block_nbytes;
      skip_block_bitmap:

            if (!inode_bitmap || !do_inode)
                  continue;

            if (lazy_flag && fs->group_desc[i].bg_flags &
                EXT2_BG_INODE_UNINIT) 
                  goto skip_this_inode_bitmap;
 
            memcpy(inode_buf, inode_bitmap, inode_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, inode_buf, 
                                       inode_nbytes);
#endif
                  retval = io_channel_write_blk(fs->io, blk, 1,
                                          inode_buf);
                  if (retval)
                        return EXT2_ET_INODE_BITMAP_WRITE;
            }
      skip_this_inode_bitmap:
            inode_bitmap += inode_nbytes;

      }
      if (do_block) {
            fs->flags &= ~EXT2_FLAG_BB_DIRTY;
            ext2fs_free_mem(&block_buf);
      }
      if (do_inode) {
            fs->flags &= ~EXT2_FLAG_IB_DIRTY;
            ext2fs_free_mem(&inode_buf);
      }
      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;
      int lazy_flag = 0;
      blk_t blk;

      EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

      fs->write_bitmaps = ext2fs_write_bitmaps;

      if (EXT2_HAS_COMPAT_FEATURE(fs->super, 
                            EXT2_FEATURE_COMPAT_LAZY_BG))
            lazy_flag = 1;

      retval = ext2fs_get_mem(strlen(fs->device_name) + 80, &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(&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->image_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->image_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 (lazy_flag && fs->group_desc[i].bg_flags &
                      EXT2_BG_BLOCK_UNINIT)
                        blk = 0;
                  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, 0xff, block_nbytes);
                  block_bitmap += block_nbytes;
            }
            if (inode_bitmap) {
                  blk = fs->group_desc[i].bg_inode_bitmap;
                  if (lazy_flag && fs->group_desc[i].bg_flags &
                      EXT2_BG_INODE_UNINIT)
                        blk = 0;
                  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, 0xff, inode_nbytes);
                  inode_bitmap += inode_nbytes;
            }
      }
      return 0;
      
cleanup:
      if (do_block) {
            ext2fs_free_mem(&fs->block_map);
            fs->block_map = 0;
      }
      if (do_inode) {
            ext2fs_free_mem(&fs->inode_map);
            fs->inode_map = 0;
      }
      if (buf)
            ext2fs_free_mem(&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_write_inode_bitmap(ext2_filsys fs)
{
      return write_bitmaps(fs, 1, 0);
}

errcode_t ext2fs_write_block_bitmap (ext2_filsys fs)
{
      return write_bitmaps(fs, 0, 1);
}

errcode_t ext2fs_read_bitmaps(ext2_filsys fs)
{
      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)
{
      int do_inode = fs->inode_map && ext2fs_test_ib_dirty(fs);
      int do_block = fs->block_map && ext2fs_test_bb_dirty(fs);

      if (!do_inode && !do_block)
            return 0;

      return write_bitmaps(fs, do_inode, do_block);
}

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