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

Dave Chinner
2013-02-22T01:41:49Z

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@fromorbit.com