linux-ext4 - Re: [PATCH] ext4: fix overhead calculations in ext4

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Message-ID: <5089736F.1030509@redhat.com>
Date:	Thu, 25 Oct 2012 12:14:23 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: fix overhead calculations in ext4_statfs, again

sorry that should be "ext4_statfs" in the subject.

On 10/25/12 11:59 AM, Eric Sandeen wrote:
> "overhead" was a write-only variable in this function after commit
> 952fc18e; we set it to 0 for minixdf, or to sbi->s_overhead if !minixdf,
> but never read it again after that.
> 
> We need to use it, not sbi->s_overhead, when subtracting out overhead
> for f_blocks, or we get the wrong answer for minixdf.
> 
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
> ---
> 
> "Once more, with feeling!" ;)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index e44b233..2feaf78 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4758,7 +4758,7 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
>  
>  	buf->f_type = EXT4_SUPER_MAGIC;
>  	buf->f_bsize = sb->s_blocksize;
> -	buf->f_blocks = ext4_blocks_count(es) - EXT4_C2B(sbi, sbi->s_overhead);
> +	buf->f_blocks = ext4_blocks_count(es) - EXT4_C2B(sbi, overhead);
>  	bfree = percpu_counter_sum_positive(&sbi->s_freeclusters_counter) -
>  		percpu_counter_sum_positive(&sbi->s_dirtyclusters_counter);
>  	/* prevent underflow in case that few free space is available */
> 
> --
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