Re: [RFC] [PATCH 1/1] Nanosecond timestamps

[Dave Kleikamp <shaggy@linux.vnet.ibm.com>]

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