From: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Subject: Re: [RFC] [PATCH 1/1] Nanosecond timestamps
Date: Wed, 07 Feb 2007 15:05:39 -0600
Message-ID: <1170882340.13329.4.camel@kleikamp.austin.ibm.com>
References: <1170427790.6464.6.camel@garfield>
	 <20070206151242.GB3140@lombardij>
	 <20070207203946.GB6565@schatzie.adilger.int>
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Cc: Johann Lombardi <johann.lombardi@bull.net>,
	Kalpak Shah <kalpak@clusterfs.com>,
	linux-ext4 <linux-ext4@vger.kernel.org>, tytso <tytso@mit.edu>,
	sct <sct@redhat.com>
To: Andreas Dilger <adilger@clusterfs.com>
In-Reply-To: <20070207203946.GB6565@schatzie.adilger.int>
Sender: linux-ext4-owner@vger.kernel.org

On Wed, 2007-02-07 at 13:39 -0700, Andreas Dilger wrote:
> On Feb 06, 2007  16:12 +0100, Johann Lombardi wrote:
> > > +                       if (EXT3_SB(sb)->s_want_extra_isize <
> > > +                           le32_to_cpu(es->s_min_extra_isize))
> >                                 ^^
> > > +                               EXT3_SB(sb)->s_want_extra_isize =
> > > +                                       le32_to_cpu(es->s_min_extra_isize);
> >                                             ^^
> > Since es->s_{min,want}_extra_isize are both __u16 (BTW, shouldn't it be
> > __le16?), I think you should use le16_to_cpu() instead of le32_to_cpu().
> 
> You are right - this works fine on little endian systems, but fails on
> big endian systems where you will get the other half of the word.
> 
> This has been a bug in several places already, and I wonder if the
> le*_to_cpu() and cpu_to_le*() macros shouldn't do some type checking
> instead of just casting the variable to the specified type?

I think that sparse will catch this.  To get the endian checks you need
to do something like this:

make C=2 CF="-D__CHECK_ENDIAN__"'

-- 
David Kleikamp
IBM Linux Technology Center