Re: [PATCH 19/19] lockd: clean up 64-bit alignment fix in nsm_init_private()

["J. Bruce Fields" <bfields@fieldses.org>]

On Thu, Apr 23, 2009 at 07:33:40PM -0400, Chuck Lever wrote:
> Recently, commit ad5b365c fixed a data type alignment issue in
> nsm_init_private() by introducing put_unaligned().  We don't actually
> _require_ an unaligned access to nsm_private here.
> 
> Instead, we should always use memcpy/memcmp to access the contents of
> RPC opaque data types.  This permits us to continue to define these as
> simple character arrays, as most legacy RPC code does, and to rely on
> gcc to pack the fields in in-core structures optimally without breaking
> on platforms that require strict alignment.

OK, I'm confused.  What structures will get packed differently?

--b.

> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> 
>  fs/lockd/mon.c |   12 +++++-------
>  1 files changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
> index 5017d50..763509a 100644
> --- a/fs/lockd/mon.c
> +++ b/fs/lockd/mon.c
> @@ -16,8 +16,6 @@
>  #include <linux/sunrpc/svc.h>
>  #include <linux/lockd/lockd.h>
>  
> -#include <asm/unaligned.h>
> -
>  #define NLMDBG_FACILITY		NLMDBG_MONITOR
>  #define NSM_PROGRAM		100024
>  #define NSM_VERSION		1
> @@ -278,14 +276,14 @@ static struct nsm_handle *nsm_lookup_priv(const struct nsm_private *priv)
>   */
>  static void nsm_init_private(struct nsm_handle *nsm)
>  {
> -	u64 *p = (u64 *)&nsm->sm_priv.data;
>  	struct timespec ts;
> -	s64 ns;
> +	u64 buf[2];
>  
>  	ktime_get_ts(&ts);
> -	ns = timespec_to_ns(&ts);
> -	put_unaligned(ns, p);
> -	put_unaligned((unsigned long)nsm, p + 1);
> +	buf[0] = timespec_to_ns(&ts);
> +	buf[1] = (unsigned long)nsm;
> +
> +	memcpy(nsm->sm_priv.data, buf, SM_PRIV_SIZE);
>  }
>  
>  static struct nsm_handle *nsm_create_handle(const struct sockaddr *sap,
>