Re: [PATCH 2/2] xfs: don't take addresses of packed xfs_rmap_key

Darrick J. Wong
2020-01-29T17:58:46Z

On Wed, Jan 29, 2020 at 11:45:05AM -0600, Eric Sandeen wrote:
> gcc now warns about taking an address of a packed structure member.
>
> This happens here because of how be32_add_cpu() works; just open-code
> the modification using a temporary variable instead.
>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
>
> diff --git a/fs/xfs/libxfs/xfs_rmap_btree.c b/fs/xfs/libxfs/xfs_rmap_btree.c
> index fc78efa52c94..ad5ead62c992 100644
> --- a/fs/xfs/libxfs/xfs_rmap_btree.c
> +++ b/fs/xfs/libxfs/xfs_rmap_btree.c
> @@ -182,12 +182,14 @@ xfs_rmapbt_init_high_key_from_rec(
> union xfs_btree_rec *rec)
> {
> uint64_t off;
> + xfs_agblock_t start;
> int adj;
>
> adj = be32_to_cpu(rec->rmap.rm_blockcount) - 1;
>
> key->rmap.rm_startblock = rec->rmap.rm_startblock;

I was gonna say to kill this statement since you set it again two lines
later, but then spotted a bug two lines down...

> - be32_add_cpu(&key->rmap.rm_startblock, adj);
> + start = be32_to_cpu(rec->rmap.rm_startblock) - adj;
> + rec->rmap.rm_startblock = cpu_to_be32(start);

...this should be setting key->rmap.rm_startblock.

--D

> key->rmap.rm_owner = rec->rmap.rm_owner;
> key->rmap.rm_offset = rec->rmap.rm_offset;
> if (XFS_RMAP_NON_INODE_OWNER(be64_to_cpu(rec->rmap.rm_owner)) ||
>
>