linux-ext4 - Re: [PATCH] ext2/ext3/ext4: Add block bitmap validation

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Message-Id: <1186127051.3866.12.camel@garfield>
Date:	Fri, 03 Aug 2007 13:14:11 +0530
From:	Kalpak Shah <kalpak@...sterfs.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	cmm@...ibm.com, linux-ext4@...r.kernel.org,
	Andreas Dilger <adilger@...sterfs.com>
Subject: Re: [PATCH] ext2/ext3/ext4: Add block bitmap validation

On Fri, 2007-08-03 at 12:40 +0530, Aneesh Kumar K.V wrote:
>  	desc = ext2_get_group_desc (sb, block_group, NULL);
>  	if (!desc)
> -		goto error_out;
> -	bh = sb_bread(sb, le32_to_cpu(desc->bg_block_bitmap));
> +		return NULL;
> +	bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
> +	bh = sb_bread(sb, bitmap_blk);
>  	if (!bh)
> -		ext2_error (sb, "read_block_bitmap",
> +		ext2_error (sb, __FUNCTION__,
>  			    "Cannot read block bitmap - "
>  			    "block_group = %d, block_bitmap = %u",
>  			    block_group, le32_to_cpu(desc->bg_block_bitmap));

bitmap_blk should be used here instead of
le32_to_cpu(desc->bg_block_bitmap). It reduces one endianness
conversion.

> -error_out:
> +
> +	/* check whether block bitmap block number is set */
> +	if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
> +		/* bad block bitmap */
> +		goto error_out;
> +	}
> +	/* check whether the inode bitmap block number is set */
> +	bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
> +	if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
> +		/* bad block bitmap */
> +		goto error_out;
> +	}
> +	/* check whether the inode table block number is set */
> +	bitmap_blk = le32_to_cpu(desc->bg_inode_table);
> +	for (i = 0; i < EXT2_SB(sb)->s_itb_per_group; i++, bitmap_blk++) {
> +		if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
> +			/* bad block bitmap */
> +			goto error_out;
> +		}
> +	}

Why not reduce a lot of this code by having:
int block_range_in_use(ext4_fsblk_t start_blk, ext4_fsblk_t num_blks,
struct super_block *sb, unsigned char *map)?

It will also help to do away with a lot of repetitive calculations in
block_in_use().

> +	ext3_error(sb, __FUNCTION__,
> +			"Invalid block bitmap - "
> +			"block_group = %d, block = %lu",
> +			block_group, bitmap_blk);

Please align this according to kernel coding style.

Thanks,
Kalpak.

-
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