On Apr 28, 2009, at 12:40 PM, J. Bruce Fields wrote:
On Tue, Apr 28, 2009 at 12:35:50PM -0400, Chuck Lever wrote:
On Apr 28, 2009, at 12:31 PM, J. Bruce Fields wrote:
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?
Any struct that has an nsm_private embedded in it, such as struct
nlm_reboot.
I don't see how that or any structure is changed by this patch.
It's not. Note the phrase above in the description: "permits us to
_continue_ to define these" -- meaning, I'm not changing the structures.
It has been suggested that we use a union or __aligned attribute for
RPC opaques. The problem with that is that it would cause structs
like nlm_reboot to balloon in size; char x[] is aligned on bytes, but
a union of u8, u32, and u64 would be aligned on a double-word
boundary. That would make such structures larger.
Legacy RPC code, and any code generated by rpcgen, generally defines
an opaque as a character array. So again, using a union would be
inconsistent with other uses of RPC opaques.
The point is we want to define and access RPC opaque's consistently,
using memset() and memcpy(), since these are nothing more than byte
arrays. The code in nsm_init_private() was an exception to this, for
no reason. We don't really need special alignment macros in there, as
long as we access the RPC opaque field with the byte sets and copies.
Would it help if I described this patch as a "clean up" ?
--b.
--b.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
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,
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
--
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