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

[Dave Chinner <david@fromorbit.com>]

On Sat, Nov 09, 2019 at 04:18:03PM -0800, Darrick J. Wong wrote:
> 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>
> > > -		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.

I was more commenting on the new code. The old code is horrible,
yes, but I don't think the new code is much better. :(

> > >  			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?

Look at what quoting did to it - it'll look the same as above in
patches, unfortunately, so I don't think "short as possible" works
any better.

Perhaps s/IFBAD/XFS_CORRUPT_IF/ ?

		XFS_CORRUPT_IF(be32_to_cpu(sib_info->back) != last_blkno ||
				sib_info->magic != dead_info->magic)) {
			xfs_error(mp, "user readable error message");
			return -EFSCORRUPTED;
		}

That solves the patch/quote indent problem, documents the code well,
and only sacrifices a single tab for the condition statements...

/me gets back on his bike and leaves the shed coated in wet paint.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com