[PATCH 10/9] xfs: fix dir3 freespace block corruption

[Ben Myers]

On Tue, May 28, 2013 at 06:37:17PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> When the directory freespace index grows to a second block (2017
> 4k data blocks in the directory), the initialisation of the second
> new block header goes wrong. The write verifier fires a corruption
> error indicating that the block number in the header is zero. This
> was being tripped by xfs/110.
> 
> The problem is that the initialisation of the new block is done just
> fine in xfs_dir3_free_get_buf(), but the caller then users a dirv2
> structure to zero on-disk header fields that xfs_dir3_free_get_buf()
> has already zeroed. These lined up with the block number in the dir
> v3 header format.
> 
> While looking at this, I noticed that the struct xfs_dir3_free_hdr()
> had 4 bytes of padding in it that wasn't defined as padding or being
> zeroed by the initialisation. Add a pad field declaration and fully
> zero the on disk and in-core headers in xfs_dir3_free_get_buf() so
> that this is never an issue in the future. Note that this doesn't
> change the on-disk layout, just makes the 32 bits of padding in the
> layout explicit.
> 
> Signed-off-by: Dave Chinner <dchinner at redhat.com>
> ---
>  fs/xfs/xfs_dir2_format.h |    1 +
>  fs/xfs/xfs_dir2_node.c   |   13 ++++++-------
>  2 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/xfs/xfs_dir2_format.h b/fs/xfs/xfs_dir2_format.h
> index a3b1bd8..995f1f5 100644
> --- a/fs/xfs/xfs_dir2_format.h
> +++ b/fs/xfs/xfs_dir2_format.h
> @@ -715,6 +715,7 @@ struct xfs_dir3_free_hdr {
>  	__be32			firstdb;	/* db of first entry */
>  	__be32			nvalid;		/* count of valid entries */
>  	__be32			nused;		/* count of used entries */
> +	__be32			pad;		/* 64 bit alignment. */

Yeah, my count also puts nused short of 64 bit alignment.  Looks ok.

Reviewed-by: Ben Myers <bpm at sgi.com>