linux-ext4 - Re: [PATCH 1/2] ext4: Make ext4_block_in

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Message-ID: <20130327030555.GB5861@thunk.org>
Date:	Tue, 26 Mar 2013 23:05:55 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/2] ext4: Make ext4_block_in_group() much more efficient

On Mon, Mar 25, 2013 at 11:24:10AM +0100, Lukas Czerner wrote:
> +	actual_group = (le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block) +
> +			block) >>
> +		       (EXT4_BLOCK_SIZE_BITS(sb) + EXT4_CLUSTER_BITS(sb) + 3);

The problem with this change is that you are assuming that the number
of blocks per group is equal to block_size * 8.  This is not always
the case; a nonstandard number of blocks per group can be set using
mke2fs's -g option.

						- Ted
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