linux-ext4 - Re: [PATCH] jbd2: Fix block tag checksum verification brokenness

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Message-ID: <20130508230339.GC25399@ZenIV.linux.org.uk>
Date:	Thu, 9 May 2013 00:03:39 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	Andreas Dilger <adilger@...ger.ca>, Theodore Ts'o <tytso@....edu>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] jbd2: Fix block tag checksum verification brokenness

On Wed, May 08, 2013 at 03:00:27PM -0700, Darrick J. Wong wrote:
> +	crc = csum32 & 0xFFFF;
>  
> -	tag->t_checksum = cpu_to_be32(csum);
> +	tag->t_checksum = cpu_to_be16(crc);

Simple cpu_to_be16(csum) will do - it'll convert the argument to __u16,
which will do exactly the same thing your & 0xFFFF is doing.  Matter of
taste...

> +	crc = csum32 & 0xFFFF;
> +	provided = be16_to_cpu(tag->t_checksum);
>  
> -	return provided == cpu_to_be32(calculated);
> +	return provided == crc;

I'd go for tag->t_checksum == cpu_to_be16(calculated) - less cluttered that
way, IMO.  Again, a matter of taste.  ACK, as far as correctness is concerned.
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