[PATCH 46/48] libxfs: fix dir3 freespace block corruption

[Ben Myers]

On Fri, Jun 07, 2013 at 10:26:09AM +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>

Goes with commit 5170711df79b28

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