Re: [PATCH 3/9] xfs: add CRC checks to the AGF

[Dave Chinner <david@xxxxxxxxxxxxx>]

On Thu, Feb 21, 2013 at 04:53:05PM -0600, Ben Myers wrote:
> > @@ -83,6 +100,7 @@ typedef struct xfs_agf {
> >  #define    XFS_AGF_FREEBLKS        0x00000200
> >  #define    XFS_AGF_LONGEST         0x00000400
> >  #define    XFS_AGF_BTREEBLKS       0x00000800
> > +#define    XFS_AGF_UUID            0x00001000
> >  #define    XFS_AGF_NUM_BITS        12
>                                       13 ?
> You added a 13th bit.

Yup, good catch.

> How do you envision having the uuid in these structures will be helpful?

Same as for all the rest of the metadata. It identifies the
filesystem it belongs to so we can detect and trace misplaced writes
instantly, rather than, say, having to spend months of debugging
with FC analysers to prove the storage array firmware has a bug in
it and that's what is causing the filesystem corruption.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx