Re: [PATCH v2] xfs: check da node block pad field during scrub

[Dave Chinner]

On Wed, Apr 08, 2026 at 06:40:34PM +0100, Yuto Ohnuki wrote:
> The da node block header (xfs_da3_node_hdr) contains a __pad32 field
> that should always be zero. Add a check for this during directory and
> attribute btree scrubbing.
> 
> Since old kernels may have written non-zero padding without issues, flag
> this as an optimization opportunity (preen) rather than corruption.
> 
> Signed-off-by: Yuto Ohnuki <ytohnuki@xxxxxxxxxx>
> ---
> Changes in v2:
> - Use xchk_da_set_preen instead of xchk_da_set_corrupt since
>   old kernels may have written non-zero padding without issues.
> - Link to v1: https://lore.kernel.org/all/20260404143043.65268-2-ytohnuki@xxxxxxxxxx/
> ---
>  fs/xfs/scrub/dabtree.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/scrub/dabtree.c b/fs/xfs/scrub/dabtree.c
> index 1a71d36898b1..b55922d3e988 100644
> --- a/fs/xfs/scrub/dabtree.c
> +++ b/fs/xfs/scrub/dabtree.c
> @@ -454,7 +454,12 @@ xchk_da_btree_block(
>  			}
>  		}
>  
> -		/* XXX: Check hdr3.pad32 once we know how to fix it. */
> +		if (xfs_has_crc(ip->i_mount)) {
> +			struct xfs_da3_node_hdr *nodehdr3 = blk->bp->b_addr;
> +
> +			if (be32_to_cpu(nodehdr3->__pad32) != 0)
> +				xchk_da_set_preen(ds, level);
> +		}

Endian conversion not necessary on comaprison to zero.

-Dave.
-- 
Dave Chinner
dgc@xxxxxxxxxx