[PATCH 07/25] xfs: verify AGI blocks as they are read from disk

[Phil White]

On Thu, Oct 25, 2012 at 05:33:56PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> Add an AGI block verify callback function and pass it into the
> buffer read functions. Remove the now redundant verification code
> that is currently in use.
> 
> Signed-off-by: Dave Chinner <dchinner at redhat.com>
> Reviewed-by: Christoph Hellwig <hch at lst.de>
> ---
>  fs/xfs/xfs_ialloc.c |   47 ++++++++++++++++++++++++++---------------------
>  1 file changed, 26 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/xfs/xfs_ialloc.c b/fs/xfs/xfs_ialloc.c
> index 7c944e1..9311ae5 100644
> --- a/fs/xfs/xfs_ialloc.c
> +++ b/fs/xfs/xfs_ialloc.c
> @@ -1472,6 +1472,31 @@ xfs_check_agi_unlinked(
>  #define xfs_check_agi_unlinked(agi)
>  #endif
>  
> +static void
> +xfs_agi_read_verify(
> +	struct xfs_buf	*bp)
> +{
> +	struct xfs_mount *mp = bp->b_target->bt_mount;
> +	struct xfs_agi	*agi = XFS_BUF_TO_AGI(bp);
> +	int		agi_ok;
> +
> +	/*
> +	 * Validate the magic number of the agi block.
> +	 */
> +	agi_ok = agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC) &&
> +		XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum)) &&
> +		be32_to_cpu(agi->agi_seqno) == bp->b_pag->pag_agno;
> +	if (unlikely(XFS_TEST_ERROR(!agi_ok, mp, XFS_ERRTAG_IALLOC_READ_AGI,
> +			XFS_RANDOM_IALLOC_READ_AGI))) {
> +		XFS_CORRUPTION_ERROR("xfs_read_agi", XFS_ERRLEVEL_LOW,
> +				     mp, agi);
> +		xfs_buf_ioerror(bp, EFSCORRUPTED);
> +	}
> +	xfs_check_agi_unlinked(agi);
> +	bp->b_iodone = NULL;
> +	xfs_buf_ioend(bp, 0);
> +}
> +

In like fashion, shouldn't this be XFS_CORRUPTION_ERROR("xfs_agi_read_verify",
...)?  In principle, it might be called from somewhere else in the future.

-Phil