Re: [PATCH 2/2] xfs: convert open coded corruption check to use XFS_IS_CORRUPT

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sun, Nov 10, 2019 at 09:32:38AM +1100, Dave Chinner wrote:
> On Thu, Nov 07, 2019 at 11:05:21PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Convert the last of the open coded corruption check and report idioms to
> > use the XFS_IS_CORRUPT macro.
> 
> hmmm.
> 
> > +	if (XFS_IS_CORRUPT(mp,
> > +	    ir.loaded != XFS_IFORK_NEXTENTS(ip, whichfork))) {
> 
> This pattern is weird. It looks like there are two separate logic
> statements to the if() condition, when in fact the second line is
> part of the XFS_IS_CORRUPT() macro.
> 
> It just looks wrong to me, especially when everything other
> multi-line macro is indented based on the indenting of the macro
> parameters....
> 
> Yes, in this case it looks a bit strange, too:
> 
> 	if (XFS_IS_CORRUPT(mp,
> 			   ir.loaded != XFS_IFORK_NEXTENTS(ip, whichfork))) {
> 
> but there is no mistaking it for separate logic statements.

They're all ugly, because of all the stupid identing when the
conditional gets too long.

> I kinda value being able to glance at the indent levels to see
> separate logic elements....
> 
> > -		if (unlikely(
> > -		       be32_to_cpu(sib_info->back) != last_blkno ||
> > -		       sib_info->magic != dead_info->magic)) {
> > -			XFS_ERROR_REPORT("xfs_da_swap_lastblock(3)",
> > -					 XFS_ERRLEVEL_LOW, mp);
> > +		if (XFS_IS_CORRUPT(mp,
> > +		    be32_to_cpu(sib_info->back) != last_blkno ||
> > +		    sib_info->magic != dead_info->magic)) {

They're both ugly, IMHO.  One has horrible indentation that's too close
to the code in the if statement body, the other is hard to read as an if
statement.

> >  			error = -EFSCORRUPTED;
> >  			goto done;
> >  		}
> 
> This is kind of what I mean - is it two or three  logic statments
> here? No, it's actually one, but it has two nested checks...
> 
> There's a few other list this that are somewhat non-obvious as to
> the logic...

I'd thought about giving it the shortest name possible, not bothering to
log the fsname that goes with the error report, and making the if part
of the macro:

#define IFBAD(cond) if ((unlikely(cond) ? assert(...), true : false))

IFBAD(be32_to_cpu(sib_info->back) != last_blkno ||
      sib_info->magic != dead_info->magic)) {
	xfs_whatever();
	return -EFSCORRUPTED;
}

Is that better?

--D

> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com