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/*
 *  linux/fs/ext2/balloc.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  Enhanced block allocation by Stephen Tweedie (sct@dcs.ed.ac.uk), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */
 
/*
 * balloc.c contains the blocks allocation and deallocation routines
 */
 
/*
 * The free blocks are managed by bitmaps.  A file system contains several
 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 * block for inodes, N blocks for the inode table and data blocks.
 *
 * The file system contains group descriptors which are located after the
 * super block.  Each descriptor contains the number of the bitmap block and
 * the free blocks count in the block.  The descriptors are loaded in memory
 * when a file system is mounted (see ext2_read_super).
 */
 
#include <linux/fs.h>
#include <linux/ext2_fs.h>
#include <linux/stat.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/locks.h>
 
#include <asm/bitops.h>
#include <asm/byteorder.h>
 
#define in_range(b, first, len)		((b) >= (first) && (b) <= (first) + (len) - 1)
 
static struct ext2_group_desc * get_group_desc (struct super_block * sb,
						unsigned int block_group,
						struct buffer_head ** bh)
{
	unsigned long group_desc;
	unsigned long desc;
	struct ext2_group_desc * gdp;
 
	/*
	 * This panic should never trigger on a bad filesystem: the caller
	 * should have verified the block/group number already.
	 */
	if (block_group >= sb->u.ext2_sb.s_groups_count)
		ext2_panic (sb, "get_group_desc",
			    "block_group >= groups_count - "
			    "block_group = %d, groups_count = %lu",
			    block_group, sb->u.ext2_sb.s_groups_count);
 
	group_desc = block_group / EXT2_DESC_PER_BLOCK(sb);
	desc = block_group % EXT2_DESC_PER_BLOCK(sb);
	if (!sb->u.ext2_sb.s_group_desc[group_desc])
		ext2_panic (sb, "get_group_desc",
			    "Group descriptor not loaded - "
			    "block_group = %d, group_desc = %lu, desc = %lu",
			     block_group, group_desc, desc);
	gdp = (struct ext2_group_desc *) 
	      sb->u.ext2_sb.s_group_desc[group_desc]->b_data;
	if (bh)
		*bh = sb->u.ext2_sb.s_group_desc[group_desc];
	return gdp + desc;
}
 
/*
 * Read the bitmap for a given block_group, reading into the specified 
 * slot in the superblock's bitmap cache.
 *
 * Return >=0 on success or a -ve error code.
 */
 
static int read_block_bitmap (struct super_block * sb,
			      unsigned int block_group,
			      unsigned long bitmap_nr)
{
	struct ext2_group_desc * gdp;
	struct buffer_head * bh;
	int retval = 0;
 
	gdp = get_group_desc (sb, block_group, NULL);
	bh = bread (sb->s_dev, swab32(gdp->bg_block_bitmap), sb->s_blocksize);
	if (!bh) {
		ext2_error (sb, "read_block_bitmap",
			    "Cannot read block bitmap - "
			    "block_group = %d, block_bitmap = %lu",
			    block_group, (unsigned long) swab32(gdp->bg_block_bitmap));
		retval = -EIO;
	}
	/*
	 * On IO error, just leave a zero in the superblock's block pointer for
	 * this group.  The IO will be retried next time.
	 */
	sb->u.ext2_sb.s_block_bitmap_number[bitmap_nr] = block_group;
	sb->u.ext2_sb.s_block_bitmap[bitmap_nr] = bh;
	return retval;
}
 
/*
 * load_block_bitmap loads the block bitmap for a blocks group
 *
 * It maintains a cache for the last bitmaps loaded.  This cache is managed
 * with a LRU algorithm.
 *
 * Notes:
 * 1/ There is one cache per mounted file system.
 * 2/ If the file system contains less than EXT2_MAX_GROUP_LOADED groups,
 *    this function reads the bitmap without maintaining a LRU cache.
 *
 * Return the slot used to store the bitmap, or a -ve error code.
 */
static int load__block_bitmap (struct super_block * sb,
			       unsigned int block_group)
{
	int i, j, retval = 0;
	unsigned long block_bitmap_number;
	struct buffer_head * block_bitmap;
 
	if (block_group >= sb->u.ext2_sb.s_groups_count)
		ext2_panic (sb, "load_block_bitmap",
			    "block_group >= groups_count - "
			    "block_group = %d, groups_count = %lu",
			    block_group, sb->u.ext2_sb.s_groups_count);
 
	if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED) {
		if (sb->u.ext2_sb.s_block_bitmap[block_group]) {
			if (sb->u.ext2_sb.s_block_bitmap_number[block_group] !=
			    block_group)
				ext2_panic (sb, "load_block_bitmap",
					    "block_group != block_bitmap_number");
			else
				return block_group;
		} else {
			retval = read_block_bitmap (sb, block_group, block_group);
			if (retval < 0)
				return retval;
			return block_group;
		}
	}
 
	for (i = 0; i < sb->u.ext2_sb.s_loaded_block_bitmaps &&
		    sb->u.ext2_sb.s_block_bitmap_number[i] != block_group; i++)
		;
	if (i < sb->u.ext2_sb.s_loaded_block_bitmaps &&
  	    sb->u.ext2_sb.s_block_bitmap_number[i] == block_group) {
		block_bitmap_number = sb->u.ext2_sb.s_block_bitmap_number[i];
		block_bitmap = sb->u.ext2_sb.s_block_bitmap[i];
		for (j = i; j > 0; j--) {
			sb->u.ext2_sb.s_block_bitmap_number[j] =
				sb->u.ext2_sb.s_block_bitmap_number[j - 1];
			sb->u.ext2_sb.s_block_bitmap[j] =
				sb->u.ext2_sb.s_block_bitmap[j - 1];
		}
		sb->u.ext2_sb.s_block_bitmap_number[0] = block_bitmap_number;
		sb->u.ext2_sb.s_block_bitmap[0] = block_bitmap;
 
		/*
		 * There's still one special case here --- if block_bitmap == 0
		 * then our last attempt to read the bitmap failed and we have
		 * just ended up caching that failure.  Try again to read it.
		 */
		if (!block_bitmap)
			retval = read_block_bitmap (sb, block_group, 0);
	} else {
		if (sb->u.ext2_sb.s_loaded_block_bitmaps < EXT2_MAX_GROUP_LOADED)
			sb->u.ext2_sb.s_loaded_block_bitmaps++;
		else
			brelse (sb->u.ext2_sb.s_block_bitmap[EXT2_MAX_GROUP_LOADED - 1]);
		for (j = sb->u.ext2_sb.s_loaded_block_bitmaps - 1; j > 0;  j--) {
			sb->u.ext2_sb.s_block_bitmap_number[j] =
				sb->u.ext2_sb.s_block_bitmap_number[j - 1];
			sb->u.ext2_sb.s_block_bitmap[j] =
				sb->u.ext2_sb.s_block_bitmap[j - 1];
		}
		retval = read_block_bitmap (sb, block_group, 0);
	}
	return retval;
}
 
/*
 * Load the block bitmap for a given block group.  First of all do a couple
 * of fast lookups for common cases and then pass the request onto the guts
 * of the bitmap loader.
 *
 * Return the slot number of the group in the superblock bitmap cache's on
 * success, or a -ve error code.
 *
 * There is still one inconsistancy here --- if the number of groups in this
 * filesystems is <= EXT2_MAX_GROUP_LOADED, then we have no way of 
 * differentiating between a group for which we have never performed a bitmap
 * IO request, and a group for which the last bitmap read request failed.
 */
static inline int load_block_bitmap (struct super_block * sb,
				     unsigned int block_group)
{
	int slot;
 
	/*
	 * Do the lookup for the slot.  First of all, check if we're asking
	 * for the same slot as last time, and did we succeed that last time?
	 */
	if (sb->u.ext2_sb.s_loaded_block_bitmaps > 0 &&
	    sb->u.ext2_sb.s_block_bitmap_number[0] == block_group &&
	    sb->u.ext2_sb.s_block_bitmap[block_group]) {
		slot = 0;
	}
	/*
	 * Or can we do a fast lookup based on a loaded group on a filesystem
	 * small enough to be mapped directly into the superblock?
	 */
	else if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED && 
		 sb->u.ext2_sb.s_block_bitmap_number[block_group] == block_group &&
		 sb->u.ext2_sb.s_block_bitmap[block_group]) {
		slot = block_group;
	} 
	/*
	 * If not, then do a full lookup for this block group.
	 */
	else {
		slot = load__block_bitmap (sb, block_group);
	}
 
	/*
	 * <0 means we just got an error
	 */
	if (slot < 0)
		return slot;
 
	/*
	 * If it's a valid slot, we may still have cached a previous IO error,
	 * in which case the bh in the superblock cache will be zero.
	 */
	if (!sb->u.ext2_sb.s_block_bitmap[slot])
		return -EIO;
 
	/*
	 * Must have been read in OK to get this far.
	 */
	return slot;
}
 
void ext2_free_blocks (const struct inode * inode, unsigned long block,
		       unsigned long count)
{
	struct buffer_head * bh;
	struct buffer_head * bh2;
	unsigned long block_group;
	unsigned long bit;
	unsigned long i;
	int bitmap_nr;
	struct super_block * sb;
	struct ext2_group_desc * gdp;
	struct ext2_super_block * es;
 
	sb = inode->i_sb;
	if (!sb) {
		printk ("ext2_free_blocks: nonexistent device");
		return;
	}
	lock_super (sb);
	es = sb->u.ext2_sb.s_es;
	if (block < swab32(es->s_first_data_block) || 
	    (block + count) > swab32(es->s_blocks_count)) {
		ext2_error (sb, "ext2_free_blocks",
			    "Freeing blocks not in datazone - "
			    "block = %lu, count = %lu", block, count);
		unlock_super (sb);
		return;
	}
 
	ext2_debug ("freeing block %lu\n", block);
 
	block_group = (block - swab32(es->s_first_data_block)) /
		      EXT2_BLOCKS_PER_GROUP(sb);
	bit = (block - swab32(es->s_first_data_block)) % EXT2_BLOCKS_PER_GROUP(sb);
	if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
		ext2_error (sb, "ext2_free_blocks",
			    "Freeing blocks across group boundary - "
			    "Block = %lu, count = %lu",
			    block, count);
		unlock_super (sb);
		return;
	}
 
	bitmap_nr = load_block_bitmap (sb, block_group);
	if (bitmap_nr < 0)
		goto error_return;
 
	bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
	gdp = get_group_desc (sb, block_group, &bh2);
 
	if (test_opt (sb, CHECK_STRICT) &&
	    (in_range (swab32(gdp->bg_block_bitmap), block, count) ||
	     in_range (swab32(gdp->bg_inode_bitmap), block, count) ||
	     in_range (block, swab32(gdp->bg_inode_table),
		       sb->u.ext2_sb.s_itb_per_group) ||
	     in_range (block + count - 1, swab32(gdp->bg_inode_table),
		       sb->u.ext2_sb.s_itb_per_group))) {
		ext2_error (sb, "ext2_free_blocks",
			    "Freeing blocks in system zones - "
			    "Block = %lu, count = %lu",
			    block, count);
		unlock_super (sb);
		return;
	}
 
	for (i = 0; i < count; i++) {
		if (!__ext2_clear_bit (bit + i, bh->b_data))
			ext2_warning (sb, "ext2_free_blocks",
				      "bit already cleared for block %lu", 
				      block);
		else {
			if (sb->dq_op)
				sb->dq_op->free_block(inode, fs_to_dq_blocks(1, sb->s_blocksize));
			gdp->bg_free_blocks_count =
				swab16(swab16(gdp->bg_free_blocks_count)+1);
			es->s_free_blocks_count =
				swab32(swab32(es->s_free_blocks_count)+1);
		}
	}
 
	mark_buffer_dirty(bh2, 1);
	mark_buffer_dirty(sb->u.ext2_sb.s_sbh, 1);
 
	mark_buffer_dirty(bh, 1);
	if (sb->s_flags & MS_SYNCHRONOUS) {
		ll_rw_block (WRITE, 1, &bh);
		wait_on_buffer (bh);
	}
	sb->s_dirt = 1;
error_return:
	unlock_super (sb);
	return;
}
 
/*
 * ext2_new_block uses a goal block to assist allocation.  If the goal is
 * free, or there is a free block within 32 blocks of the goal, that block
 * is allocated.  Otherwise a forward search is made for a free block; within 
 * each block group the search first looks for an entire free byte in the block
 * bitmap, and then for any free bit if that fails.
 */
int ext2_new_block (const struct inode * inode, unsigned long goal,
		    u32 * prealloc_count, u32 * prealloc_block, int * err)
{
	struct buffer_head * bh;
	struct buffer_head * bh2;
	char * p, * r;
	int i, j, k, tmp;
	int bitmap_nr;
	struct super_block * sb;
	struct ext2_group_desc * gdp;
	struct ext2_super_block * es;
 
	*err = -ENOSPC;
#ifdef EXT2FS_DEBUG
	static int goal_hits = 0, goal_attempts = 0;
#endif
	sb = inode->i_sb;
	if (!sb) {
		printk ("ext2_new_block: nonexistent device");
		return 0;
	}
	lock_super (sb);
	es = sb->u.ext2_sb.s_es;
	if (swab32(es->s_free_blocks_count) <= swab32(es->s_r_blocks_count) &&
	    (!fsuser() && (sb->u.ext2_sb.s_resuid != current->fsuid) &&
	     (sb->u.ext2_sb.s_resgid == 0 ||
	      !in_group_p (sb->u.ext2_sb.s_resgid)))) {
		unlock_super (sb);
		return 0;
	}
 
	ext2_debug ("goal=%lu.\n", goal);
 
repeat:
	/*
	 * First, test whether the goal block is free.
	 */
	if (goal < swab32(es->s_first_data_block) || goal >= swab32(es->s_blocks_count))
		goal = swab32(es->s_first_data_block);
	i = (goal - swab32(es->s_first_data_block)) / EXT2_BLOCKS_PER_GROUP(sb);
	gdp = get_group_desc (sb, i, &bh2);
	if (swab16(gdp->bg_free_blocks_count) > 0) {
		j = ((goal - swab32(es->s_first_data_block)) % EXT2_BLOCKS_PER_GROUP(sb));
#ifdef EXT2FS_DEBUG
		if (j)
			goal_attempts++;
#endif
		bitmap_nr = load_block_bitmap (sb, i);
		if (bitmap_nr < 0) {
			*err = -EIO;
			unlock_super (sb);
			return 0;
		}
 
		bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
 
		ext2_debug ("goal is at %d:%d.\n", i, j);
 
		if (!__ext2_test_bit(j, bh->b_data)) {
#ifdef EXT2FS_DEBUG
			goal_hits++;
			ext2_debug ("goal bit allocated.\n");
#endif
			goto got_block;
		}
		if (j) {
			/*
			 * The goal was occupied; search forward for a free 
			 * block within the next XX blocks.
			 *
			 * end_goal is more or less random, but it has to be
			 * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the
			 * next 64-bit boundary is simple..
			 */
			int end_goal = (j + 63) & ~63;
			j = __ext2_find_next_zero_bit(bh->b_data, end_goal, j);
			if (j < end_goal)
				goto got_block;
		}
 
		ext2_debug ("Bit not found near goal\n");
 
		/*
		 * There has been no free block found in the near vicinity
		 * of the goal: do a search forward through the block groups,
		 * searching in each group first for an entire free byte in
		 * the bitmap and then for any free bit.
		 * 
		 * Search first in the remainder of the current group; then,
		 * cyclicly search through the rest of the groups.
		 */
		p = ((char *) bh->b_data) + (j >> 3);
		r = memscan(p, 0, (EXT2_BLOCKS_PER_GROUP(sb) - j + 7) >> 3);
		k = (r - ((char *) bh->b_data)) << 3;
		if (k < EXT2_BLOCKS_PER_GROUP(sb)) {
			j = k;
			goto search_back;
		}
		k = __ext2_find_next_zero_bit ((unsigned long *) bh->b_data, 
					EXT2_BLOCKS_PER_GROUP(sb),
					j);
		if (k < EXT2_BLOCKS_PER_GROUP(sb)) {
			j = k;
			goto got_block;
		}
	}
 
	ext2_debug ("Bit not found in block group %d.\n", i);
 
	/*
	 * Now search the rest of the groups.  We assume that 
	 * i and gdp correctly point to the last group visited.
	 */
	for (k = 0; k < sb->u.ext2_sb.s_groups_count; k++) {
		i++;
		if (i >= sb->u.ext2_sb.s_groups_count)
			i = 0;
		gdp = get_group_desc (sb, i, &bh2);
		if (swab16(gdp->bg_free_blocks_count) > 0)
			break;
	}
	if (k >= sb->u.ext2_sb.s_groups_count) {
		unlock_super (sb);
		return 0;
	}
 
	bitmap_nr = load_block_bitmap (sb, i);
	if (bitmap_nr < 0) {
		*err = -EIO;
		unlock_super (sb);
		return 0;
	}
 
	bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
	r = memscan(bh->b_data, 0, EXT2_BLOCKS_PER_GROUP(sb) >> 3);
	j = (r - bh->b_data) << 3;
	if (j < EXT2_BLOCKS_PER_GROUP(sb))
		goto search_back;
	else
		j = __ext2_find_first_zero_bit ((unsigned long *) bh->b_data,
					 EXT2_BLOCKS_PER_GROUP(sb));
	if (j >= EXT2_BLOCKS_PER_GROUP(sb)) {
		ext2_error (sb, "ext2_new_block",
			    "Free blocks count corrupted for block group %d", i);
		unlock_super (sb);
		return 0;
	}
 
search_back:
	/* 
	 * We have succeeded in finding a free byte in the block
	 * bitmap.  Now search backwards up to 7 bits to find the
	 * start of this group of free blocks.
	 */
	for (k = 0; k < 7 && j > 0 && !__ext2_test_bit (j - 1, bh->b_data); k++, j--);
 
got_block:
 
	ext2_debug ("using block group %d(%d)\n", i, gdp->bg_free_blocks_count);
 
	/*
	 * Check quota for allocation of this block.
	 */
	if (sb->dq_op)
		if (sb->dq_op->alloc_block (inode, fs_to_dq_blocks(1, sb->s_blocksize))) {
			unlock_super (sb);
			*err = -EDQUOT;
			return 0;
		}
 
	tmp = j + i * EXT2_BLOCKS_PER_GROUP(sb) + swab32(es->s_first_data_block);
 
	if (test_opt (sb, CHECK_STRICT) &&
	    (tmp == swab32(gdp->bg_block_bitmap) ||
	     tmp == swab32(gdp->bg_inode_bitmap) ||
	     in_range (tmp, swab32(gdp->bg_inode_table), sb->u.ext2_sb.s_itb_per_group))) {
		ext2_error (sb, "ext2_new_block",
			    "Allocating block in system zone - "
			    "block = %u", tmp);
		unlock_super (sb);
		*err = -EIO;
		return 0;
	}
 
	if (__ext2_set_bit (j, bh->b_data)) {
		ext2_warning (sb, "ext2_new_block",
			      "bit already set for block %d", j);
		if (sb->dq_op)
			sb->dq_op->free_block(inode, fs_to_dq_blocks(1, sb->s_blocksize));
		goto repeat;
	}
 
	ext2_debug ("found bit %d\n", j);
 
	/*
	 * Do block preallocation now if required.
	 */
#ifdef EXT2_PREALLOCATE
	if (prealloc_block) {
		*prealloc_count = 0;
		*prealloc_block = tmp + 1;
		for (k = 1;
		     k < 8 && (j + k) < EXT2_BLOCKS_PER_GROUP(sb); k++) {
			if (sb->dq_op)
				if (sb->dq_op->alloc_block(inode, fs_to_dq_blocks(1, sb->s_blocksize)))
					break;
			if (__ext2_set_bit (j + k, bh->b_data)) {
				if (sb->dq_op)
					sb->dq_op->free_block(inode, fs_to_dq_blocks(1, sb->s_blocksize));
  				break;
			}
			(*prealloc_count)++;
		}	
		gdp->bg_free_blocks_count =
			swab16(swab16(gdp->bg_free_blocks_count) -
			       *prealloc_count);
		es->s_free_blocks_count =
			swab32(swab32(es->s_free_blocks_count) -
			       *prealloc_count);
		ext2_debug ("Preallocated a further %lu bits.\n",
			    *prealloc_count);
	}
#endif
 
	j = tmp;
 
	mark_buffer_dirty(bh, 1);
	if (sb->s_flags & MS_SYNCHRONOUS) {
		ll_rw_block (WRITE, 1, &bh);
		wait_on_buffer (bh);
	}
 
	if (j >= swab32(es->s_blocks_count)) {
		ext2_error (sb, "ext2_new_block",
			    "block >= blocks count - "
			    "block_group = %d, block=%d", i, j);
		unlock_super (sb);
		return 0;
	}
	if (!(bh = getblk (sb->s_dev, j, sb->s_blocksize))) {
		ext2_error (sb, "ext2_new_block", "cannot get block %d", j);
		unlock_super (sb);
		return 0;
	}
	memset(bh->b_data, 0, sb->s_blocksize);
	mark_buffer_uptodate(bh, 1);
	mark_buffer_dirty(bh, 1);
	brelse (bh);
 
	ext2_debug ("allocating block %d. "
		    "Goal hits %d of %d.\n", j, goal_hits, goal_attempts);
 
	gdp->bg_free_blocks_count = swab16(swab16(gdp->bg_free_blocks_count) - 1);
	mark_buffer_dirty(bh2, 1);
	es->s_free_blocks_count = swab32(swab32(es->s_free_blocks_count) - 1);
	mark_buffer_dirty(sb->u.ext2_sb.s_sbh, 1);
	sb->s_dirt = 1;
	unlock_super (sb);
	*err = 0;
	return j;
}
 
unsigned long ext2_count_free_blocks (struct super_block * sb)
{
#ifdef EXT2FS_DEBUG
	struct ext2_super_block * es;
	unsigned long desc_count, bitmap_count, x;
	int bitmap_nr;
	struct ext2_group_desc * gdp;
	int i;
 
	lock_super (sb);
	es = sb->u.ext2_sb.s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;
	for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
		gdp = get_group_desc (sb, i, NULL);
		desc_count += swab16(gdp->bg_free_blocks_count);
 
		bitmap_nr = load_block_bitmap (sb, i);
		if (bitmap_nr < 0)
			continue;
 
		x = ext2_count_free (sb->u.ext2_sb.s_block_bitmap[bitmap_nr],
				     sb->s_blocksize);
		printk ("group %d: stored = %d, counted = %lu\n",
			i, swab16(gdp->bg_free_blocks_count), x);
		bitmap_count += x;
	}
	printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
	       swab32(es->s_free_blocks_count), desc_count, bitmap_count);
	unlock_super (sb);
	return bitmap_count;
#else
	return swab32(sb->u.ext2_sb.s_es->s_free_blocks_count);
#endif
}
 
static inline int block_in_use (unsigned long block,
				struct super_block * sb,
				unsigned char * map)
{
	return __ext2_test_bit ((block - swab32(sb->u.ext2_sb.s_es->s_first_data_block)) %
			 EXT2_BLOCKS_PER_GROUP(sb), map);
}
 
void ext2_check_blocks_bitmap (struct super_block * sb)
{
	struct buffer_head * bh;
	struct ext2_super_block * es;
	unsigned long desc_count, bitmap_count, x;
	unsigned long desc_blocks;
	int bitmap_nr;
	struct ext2_group_desc * gdp;
	int i, j;
 
	lock_super (sb);
	es = sb->u.ext2_sb.s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;
	desc_blocks = (sb->u.ext2_sb.s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
		      EXT2_DESC_PER_BLOCK(sb);
	for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
		gdp = get_group_desc (sb, i, NULL);
		desc_count += swab16(gdp->bg_free_blocks_count);
		bitmap_nr = load_block_bitmap (sb, i);
		if (bitmap_nr < 0)
			continue;
 
		bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
 
		if (!__ext2_test_bit (0, bh->b_data))
			ext2_error (sb, "ext2_check_blocks_bitmap",
				    "Superblock in group %d is marked free", i);
 
		for (j = 0; j < desc_blocks; j++)
			if (!__ext2_test_bit (j + 1, bh->b_data))
				ext2_error (sb, "ext2_check_blocks_bitmap",
					    "Descriptor block #%d in group "
					    "%d is marked free", j, i);
 
		if (!block_in_use (swab32(gdp->bg_block_bitmap), sb, bh->b_data))
			ext2_error (sb, "ext2_check_blocks_bitmap",
				    "Block bitmap for group %d is marked free",
				    i);
 
		if (!block_in_use (swab32(gdp->bg_inode_bitmap), sb, bh->b_data))
			ext2_error (sb, "ext2_check_blocks_bitmap",
				    "Inode bitmap for group %d is marked free",
				    i);
 
		for (j = 0; j < sb->u.ext2_sb.s_itb_per_group; j++)
			if (!block_in_use (swab32(gdp->bg_inode_table) + j, sb, bh->b_data))
				ext2_error (sb, "ext2_check_blocks_bitmap",
					    "Block #%d of the inode table in "
					    "group %d is marked free", j, i);
 
		x = ext2_count_free (bh, sb->s_blocksize);
		if (swab16(gdp->bg_free_blocks_count) != x)
			ext2_error (sb, "ext2_check_blocks_bitmap",
				    "Wrong free blocks count for group %d, "
				    "stored = %d, counted = %lu", i,
				    swab16(gdp->bg_free_blocks_count), x);
		bitmap_count += x;
	}
	if (swab32(es->s_free_blocks_count) != bitmap_count)
		ext2_error (sb, "ext2_check_blocks_bitmap",
			    "Wrong free blocks count in super block, "
			    "stored = %lu, counted = %lu",
			    (unsigned long) swab32(es->s_free_blocks_count), bitmap_count);
	unlock_super (sb);
}