balloc.c

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

	
	if (next < maxblocks && ext3_test_allocatable(next, bh))
		return next;
	
	/* The bitmap search --- search forward alternately
	 * through the actual bitmap and the last-committed copy
	 * until we find a bit free in both. */

	while (here < maxblocks) {
		next  = ext3_find_next_zero_bit ((unsigned long *) bh->b_data, 
						 maxblocks, here);
		if (next >= maxblocks)
			return -1;
		if (ext3_test_allocatable(next, bh))
			return next;

		J_ASSERT_BH(bh, bh2jh(bh)->b_committed_data);
		here = ext3_find_next_zero_bit
			((unsigned long *) bh2jh(bh)->b_committed_data, 
			 maxblocks, next);
	}
	return -1;
}

/*
 * ext3_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.
 * This function also updates quota and i_blocks field.
 */
int ext3_new_block (handle_t *handle, struct inode * inode,
		unsigned long goal, u32 * prealloc_count,
		u32 * prealloc_block, int * errp)
{
	struct buffer_head * bh, *bhtmp;
	struct buffer_head * bh2;
#if 0
	char * p, * r;
#endif
	int i, j, k, tmp, alloctmp;
	int bitmap_nr;
	int fatal = 0, err;
	int performed_allocation = 0;
	struct super_block * sb;
	struct ext3_group_desc * gdp;
	struct ext3_super_block * es;
#ifdef EXT3FS_DEBUG
	static int goal_hits = 0, goal_attempts = 0;
#endif
	*errp = -ENOSPC;
	sb = inode->i_sb;
	if (!sb) {
		printk ("ext3_new_block: nonexistent device");
		return 0;
	}

	/*
	 * Check quota for allocation of this block.
	 */
	if (DQUOT_ALLOC_BLOCK(inode, 1)) {
		*errp = -EDQUOT;
		return 0;
	}

	lock_super (sb);
	es = sb->u.ext3_sb.s_es;
	if (le32_to_cpu(es->s_free_blocks_count) <=
			le32_to_cpu(es->s_r_blocks_count) &&
	    ((sb->u.ext3_sb.s_resuid != current->fsuid) &&
	     (sb->u.ext3_sb.s_resgid == 0 ||
	      !in_group_p (sb->u.ext3_sb.s_resgid)) && 
	     !capable(CAP_SYS_RESOURCE)))
		goto out;

	ext3_debug ("goal=%lu.\n", goal);

	/*
	 * First, test whether the goal block is free.
	 */
	if (goal < le32_to_cpu(es->s_first_data_block) ||
	    goal >= le32_to_cpu(es->s_blocks_count))
		goal = le32_to_cpu(es->s_first_data_block);
	i = (goal - le32_to_cpu(es->s_first_data_block)) /
			EXT3_BLOCKS_PER_GROUP(sb);
	gdp = ext3_get_group_desc (sb, i, &bh2);
	if (!gdp)
		goto io_error;

	if (le16_to_cpu(gdp->bg_free_blocks_count) > 0) {
		j = ((goal - le32_to_cpu(es->s_first_data_block)) %
				EXT3_BLOCKS_PER_GROUP(sb));
#ifdef EXT3FS_DEBUG
		if (j)
			goal_attempts++;
#endif
		bitmap_nr = load_block_bitmap (sb, i);
		if (bitmap_nr < 0)
			goto io_error;
		
		bh = sb->u.ext3_sb.s_block_bitmap[bitmap_nr];

		ext3_debug ("goal is at %d:%d.\n", i, j);

		if (ext3_test_allocatable(j, bh)) {
#ifdef EXT3FS_DEBUG
			goal_hits++;
			ext3_debug ("goal bit allocated.\n");
#endif
			goto got_block;
		}

		j = find_next_usable_block(j, bh, EXT3_BLOCKS_PER_GROUP(sb));
		if (j >= 0)
			goto search_back;
	}

	ext3_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.ext3_sb.s_groups_count; k++) {
		i++;
		if (i >= sb->u.ext3_sb.s_groups_count)
			i = 0;
		gdp = ext3_get_group_desc (sb, i, &bh2);
		if (!gdp) {
			*errp = -EIO;
			goto out;
		}
		if (le16_to_cpu(gdp->bg_free_blocks_count) > 0) {
			bitmap_nr = load_block_bitmap (sb, i);
			if (bitmap_nr < 0)
				goto io_error;
	
			bh = sb->u.ext3_sb.s_block_bitmap[bitmap_nr];
			j = find_next_usable_block(-1, bh, 
						   EXT3_BLOCKS_PER_GROUP(sb));
			if (j >= 0) 
				goto search_back;
		}
	}

	/* No space left on the device */
	goto out;

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 && ext3_test_allocatable(j - 1, bh);
		k++, j--)
		;
	
got_block:

	ext3_debug ("using block group %d(%d)\n", i, gdp->bg_free_blocks_count);

	/* Make sure we use undo access for the bitmap, because it is
           critical that we do the frozen_data COW on bitmap buffers in
           all cases even if the buffer is in BJ_Forget state in the
           committing transaction.  */
	BUFFER_TRACE(bh, "get undo access for marking new block");
	fatal = ext3_journal_get_undo_access(handle, bh);
	if (fatal) goto out;
	
	BUFFER_TRACE(bh2, "get_write_access");
	fatal = ext3_journal_get_write_access(handle, bh2);
	if (fatal) goto out;

	BUFFER_TRACE(sb->u.ext3_sb.s_sbh, "get_write_access");
	fatal = ext3_journal_get_write_access(handle, sb->u.ext3_sb.s_sbh);
	if (fatal) goto out;

	tmp = j + i * EXT3_BLOCKS_PER_GROUP(sb)
				+ le32_to_cpu(es->s_first_data_block);

	if (tmp == le32_to_cpu(gdp->bg_block_bitmap) ||
	    tmp == le32_to_cpu(gdp->bg_inode_bitmap) ||
	    in_range (tmp, le32_to_cpu(gdp->bg_inode_table),
		      sb->u.ext3_sb.s_itb_per_group))
		ext3_error (sb, "ext3_new_block",
			    "Allocating block in system zone - "
			    "block = %u", tmp);

	/* The superblock lock should guard against anybody else beating
	 * us to this point! */
	J_ASSERT_BH(bh, !ext3_test_bit(j, bh->b_data));
	BUFFER_TRACE(bh, "setting bitmap bit");
	ext3_set_bit(j, bh->b_data);
	performed_allocation = 1;

#ifdef CONFIG_JBD_DEBUG
	{
		struct buffer_head *debug_bh;

		/* Record bitmap buffer state in the newly allocated block */
		debug_bh = sb_get_hash_table(sb, tmp);
		if (debug_bh) {
			BUFFER_TRACE(debug_bh, "state when allocated");
			BUFFER_TRACE2(debug_bh, bh, "bitmap state");
			brelse(debug_bh);
		}
	}
#endif
	if (buffer_jbd(bh) && bh2jh(bh)->b_committed_data)
		J_ASSERT_BH(bh, !ext3_test_bit(j, bh2jh(bh)->b_committed_data));
	bhtmp = bh;
	alloctmp = j;

	ext3_debug ("found bit %d\n", j);

	/*
	 * Do block preallocation now if required.
	 */
#ifdef EXT3_PREALLOCATE
	/*
	 * akpm: this is not enabled for ext3.  Need to use
	 * ext3_test_allocatable()
	 */
	/* Writer: ->i_prealloc* */
	if (prealloc_count && !*prealloc_count) {
		int	prealloc_goal;
		unsigned long next_block = tmp + 1;

		prealloc_goal = es->s_prealloc_blocks ?
			es->s_prealloc_blocks : EXT3_DEFAULT_PREALLOC_BLOCKS;

		*prealloc_block = next_block;
		/* Writer: end */
		for (k = 1;
		     k < prealloc_goal && (j + k) < EXT3_BLOCKS_PER_GROUP(sb);
		     k++, next_block++) {
			if (DQUOT_PREALLOC_BLOCK(inode, 1))
				break;
			/* Writer: ->i_prealloc* */
			if (*prealloc_block + *prealloc_count != next_block ||
			    ext3_set_bit (j + k, bh->b_data)) {
				/* Writer: end */
				DQUOT_FREE_BLOCK(inode, 1);
 				break;
			}
			(*prealloc_count)++;
			/* Writer: end */
		}	
		/*
		 * As soon as we go for per-group spinlocks we'll need these
		 * done inside the loop above.
		 */
		gdp->bg_free_blocks_count =
			cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) -
			       (k - 1));
		es->s_free_blocks_count =
			cpu_to_le32(le32_to_cpu(es->s_free_blocks_count) -
			       (k - 1));
		ext3_debug ("Preallocated a further %lu bits.\n",
			       (k - 1));
	}
#endif

	j = tmp;

	BUFFER_TRACE(bh, "journal_dirty_metadata for bitmap block");
	err = ext3_journal_dirty_metadata(handle, bh);
	if (!fatal) fatal = err;
	
	if (j >= le32_to_cpu(es->s_blocks_count)) {
		ext3_error (sb, "ext3_new_block",
			    "block(%d) >= blocks count(%d) - "
			    "block_group = %d, es == %p ",j,
			le32_to_cpu(es->s_blocks_count), i, es);
		goto out;
	}

	/*
	 * It is up to the caller to add the new buffer to a journal
	 * list of some description.  We don't know in advance whether
	 * the caller wants to use it as metadata or data.
	 */

	ext3_debug ("allocating block %d. "
		    "Goal hits %d of %d.\n", j, goal_hits, goal_attempts);

	gdp->bg_free_blocks_count =
			cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) - 1);
	es->s_free_blocks_count =
			cpu_to_le32(le32_to_cpu(es->s_free_blocks_count) - 1);

	BUFFER_TRACE(bh2, "journal_dirty_metadata for group descriptor");
	err = ext3_journal_dirty_metadata(handle, bh2);
	if (!fatal) fatal = err;
	
	BUFFER_TRACE(bh, "journal_dirty_metadata for superblock");
	err = ext3_journal_dirty_metadata(handle, sb->u.ext3_sb.s_sbh);
	if (!fatal) fatal = err;

	sb->s_dirt = 1;
	if (fatal)
		goto out;

	unlock_super (sb);
	*errp = 0;
	return j;
	
io_error:
	*errp = -EIO;
out:
	if (fatal) {
		*errp = fatal;
		ext3_std_error(sb, fatal);
	}
	unlock_super (sb);
	/*
	 * Undo the block allocation
	 */
	if (!performed_allocation)
		DQUOT_FREE_BLOCK(inode, 1);
	return 0;
	
}

unsigned long ext3_count_free_blocks (struct super_block * sb)
{
#ifdef EXT3FS_DEBUG
	struct ext3_super_block * es;
	unsigned long desc_count, bitmap_count, x;
	int bitmap_nr;
	struct ext3_group_desc * gdp;
	int i;
	
	lock_super (sb);
	es = sb->u.ext3_sb.s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;
	for (i = 0; i < sb->u.ext3_sb.s_groups_count; i++) {
		gdp = ext3_get_group_desc (sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
		bitmap_nr = load_block_bitmap (sb, i);
		if (bitmap_nr < 0)
			continue;
		
		x = ext3_count_free (sb->u.ext3_sb.s_block_bitmap[bitmap_nr],
				     sb->s_blocksize);
		printk ("group %d: stored = %d, counted = %lu\n",
			i, le16_to_cpu(gdp->bg_free_blocks_count), x);
		bitmap_count += x;
	}
	printk("ext3_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
	       le32_to_cpu(es->s_free_blocks_count), desc_count, bitmap_count);
	unlock_super (sb);
	return bitmap_count;
#else
	return le32_to_cpu(sb->u.ext3_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 ext3_test_bit ((block -
		le32_to_cpu(sb->u.ext3_sb.s_es->s_first_data_block)) %
			 EXT3_BLOCKS_PER_GROUP(sb), map);
}

static inline int test_root(int a, int b)
{
	if (a == 0)
		return 1;
	while (1) {
		if (a == 1)
			return 1;
		if (a % b)
			return 0;
		a = a / b;
	}
}

int ext3_group_sparse(int group)
{
	return (test_root(group, 3) || test_root(group, 5) ||
		test_root(group, 7));
}

/**
 *	ext3_bg_has_super - number of blocks used by the superblock in group
 *	@sb: superblock for filesystem
 *	@group: group number to check
 *
 *	Return the number of blocks used by the superblock (primary or backup)
 *	in this group.  Currently this will be only 0 or 1.
 */
int ext3_bg_has_super(struct super_block *sb, int group)
{
	if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
	    !ext3_group_sparse(group))
		return 0;
	return 1;
}

/**
 *	ext3_bg_num_gdb - number of blocks used by the group table in group
 *	@sb: superblock for filesystem
 *	@group: group number to check
 *
 *	Return the number of blocks used by the group descriptor table
 *	(primary or backup) in this group.  In the future there may be a
 *	different number of descriptor blocks in each group.
 */
unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
{
	if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
	    !ext3_group_sparse(group))
		return 0;
	return EXT3_SB(sb)->s_gdb_count;
}

#ifdef CONFIG_EXT3_CHECK
/* Called at mount-time, super-block is locked */
void ext3_check_blocks_bitmap (struct super_block * sb)
{
	struct buffer_head * bh;
	struct ext3_super_block * es;
	unsigned long desc_count, bitmap_count, x, j;
	unsigned long desc_blocks;
	int bitmap_nr;
	struct ext3_group_desc * gdp;
	int i;

	es = sb->u.ext3_sb.s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;
	for (i = 0; i < sb->u.ext3_sb.s_groups_count; i++) {
		gdp = ext3_get_group_desc (sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
		bitmap_nr = load_block_bitmap (sb, i);
		if (bitmap_nr < 0)
			continue;

		bh = EXT3_SB(sb)->s_block_bitmap[bitmap_nr];

		if (ext3_bg_has_super(sb, i) && !ext3_test_bit(0, bh->b_data))
			ext3_error(sb, __FUNCTION__,
				   "Superblock in group %d is marked free", i);

		desc_blocks = ext3_bg_num_gdb(sb, i);
		for (j = 0; j < desc_blocks; j++)
			if (!ext3_test_bit(j + 1, bh->b_data))
				ext3_error(sb, __FUNCTION__,
					   "Descriptor block #%ld in group "
					   "%d is marked free", j, i);

		if (!block_in_use (le32_to_cpu(gdp->bg_block_bitmap),
						sb, bh->b_data))
			ext3_error (sb, "ext3_check_blocks_bitmap",
				    "Block bitmap for group %d is marked free",
				    i);

		if (!block_in_use (le32_to_cpu(gdp->bg_inode_bitmap),
						sb, bh->b_data))
			ext3_error (sb, "ext3_check_blocks_bitmap",
				    "Inode bitmap for group %d is marked free",
				    i);

		for (j = 0; j < sb->u.ext3_sb.s_itb_per_group; j++)
			if (!block_in_use (le32_to_cpu(gdp->bg_inode_table) + j,
							sb, bh->b_data))
				ext3_error (sb, "ext3_check_blocks_bitmap",
					    "Block #%d of the inode table in "
					    "group %d is marked free", j, i);

		x = ext3_count_free (bh, sb->s_blocksize);
		if (le16_to_cpu(gdp->bg_free_blocks_count) != x)
			ext3_error (sb, "ext3_check_blocks_bitmap",
				    "Wrong free blocks count for group %d, "
				    "stored = %d, counted = %lu", i,
				    le16_to_cpu(gdp->bg_free_blocks_count), x);
		bitmap_count += x;
	}
	if (le32_to_cpu(es->s_free_blocks_count) != bitmap_count)
		ext3_error (sb, "ext3_check_blocks_bitmap",
			"Wrong free blocks count in super block, "
			"stored = %lu, counted = %lu",
			(unsigned long)le32_to_cpu(es->s_free_blocks_count),
			bitmap_count);
}
#endif