[PATCH 5/9] repair: detect CRC errors in AG headers

[Dave Chinner]

On Tue, Apr 29, 2014 at 10:06:19AM -0400, Brian Foster wrote:
> On Tue, Apr 29, 2014 at 07:04:55AM +1000, Dave Chinner wrote:
> > From: Dave Chinner <dchinner at redhat.com>
> > 
> > repair doesn't currently detect verifier errors in AG header
> > blocks - apart from the primary superblock they are not detected.
> > They are, fortunately, corrected in the important cases (AGF, AGI
> > and AGFL) because these structures are rebuilt in phase 5, but if
> > you run xfs_repair in checking mode it won't report them as bad.
> > 
> > Signed-off-by: Dave Chinner <dchinner at redhat.com>
.....
> > @@ -1312,21 +1302,34 @@ scan_ag(
> >  	validate_agi(agi, agno, agcnts);
> >  
> >  	ASSERT(agi_dirty == 0 || (agi_dirty && !no_modify));
> > +	ASSERT(agf_dirty == 0 || (agf_dirty && !no_modify));
> > +	ASSERT(sb_dirty == 0 || (sb_dirty && !no_modify));
> > +
> > +	/*
> > +	 * Only pay attention to CRC/verifier errors if we can correct them.
> > +	 * While there, ensure that we corrected a corruption error if the
> > +	 * verifier detected one.
> > +	 */
> > +	if (!no_modify) {
> > +		ASSERT(agi_dirty || agibuf->b_error != EFSCORRUPTED);
> > +		ASSERT(agf_dirty || agfbuf->b_error != EFSCORRUPTED);
> > +		ASSERT(sb_dirty || sbbuf->b_error != EFSCORRUPTED);
> > +
> > +		agi_dirty += (agibuf->b_error == EFSBADCRC);
> > +		agf_dirty += (agfbuf->b_error == EFSBADCRC);
> > +		sb_dirty += (sbbuf->b_error == EFSBADCRC);
> > +	}
> 
> So we'll detect and correct the CRC error in normal mode, but no longer
> issue the preceding warnings ("would reset bad ...") for CRC errors in
> no_modify mode. Is that desired?

It will still throw a bad CRC error, so the user is still told that
there is a problem.

> I ask because it looks like a departure from previous versions.
> Otherwise, the code looks fine to me.

Slightly, but I don't think it makes much difference...

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com