[XFRM]: Pack struct xfrm_policy

[acme@newtoy net-2.6.20]$ pahole net/ipv4/tcp.o xfrm_policy
/* /pub/scm/linux/kernel/git/acme/net-2.6.20/include/linux/security.h:67 */
struct xfrm_policy {
        struct xfrm_policy *       next;                 /*     0     4 */
        struct hlist_node          bydst;                /*     4     8 */
        struct hlist_node          byidx;                /*    12     8 */
        rwlock_t                   lock;                 /*    20    36 */
        atomic_t                   refcnt;               /*    56     4 */
        struct timer_list          timer;                /*    60    24 */
        u8                         type;                 /*    84     1 */

        /* XXX 3 bytes hole, try to pack */

        u32                        priority;             /*    88     4 */
        u32                        index;                /*    92     4 */
        struct xfrm_selector       selector;             /*    96    56 */
        struct xfrm_lifetime_cfg   lft;                  /*   152    64 */
        struct xfrm_lifetime_cur   curlft;               /*   216    32 */
        struct dst_entry *         bundles;              /*   248     4 */
        __u16                      family;               /*   252     2 */
        __u8                       action;               /*   254     1 */
        __u8                       flags;                /*   255     1 */
        __u8                       dead;                 /*   256     1 */
        __u8                       xfrm_nr;              /*   257     1 */

        /* XXX 2 bytes hole, try to pack */

        struct xfrm_sec_ctx *      security;             /*   260     4 */
        struct xfrm_tmpl           xfrm_vec[6];          /*   264   360 */
}; /* size: 624, sum members: 619, holes: 2, sum holes: 5 */

So lets have just one hole instead of two, by moving 'type' to just before 'action',
end result:

[acme@newtoy net-2.6.20]$ codiff -s /tmp/tcp.o.before net/ipv4/tcp.o
/pub/scm/linux/kernel/git/acme/net-2.6.20/net/ipv4/tcp.c:
  struct xfrm_policy |   -4
 1 struct changed
[acme@newtoy net-2.6.20]$

[acme@newtoy net-2.6.20]$ pahole -c 64 net/ipv4/tcp.o xfrm_policy
/* /pub/scm/linux/kernel/git/acme/net-2.6.20/include/linux/security.h:67 */
struct xfrm_policy {
        struct xfrm_policy *       next;                 /*     0     4 */
        struct hlist_node          bydst;                /*     4     8 */
        struct hlist_node          byidx;                /*    12     8 */
        rwlock_t                   lock;                 /*    20    36 */
        atomic_t                   refcnt;               /*    56     4 */
        struct timer_list          timer;                /*    60    24 */
        u32                        priority;             /*    84     4 */
        u32                        index;                /*    88     4 */
        struct xfrm_selector       selector;             /*    92    56 */
        struct xfrm_lifetime_cfg   lft;                  /*   148    64 */
        struct xfrm_lifetime_cur   curlft;               /*   212    32 */
        struct dst_entry *         bundles;              /*   244     4 */
        u16                        family;               /*   248     2 */
        u8                         type;                 /*   250     1 */
        u8                         action;               /*   251     1 */
        u8                         flags;                /*   252     1 */
        u8                         dead;                 /*   253     1 */
        u8                         xfrm_nr;              /*   254     1 */

        /* XXX 1 byte hole, try to pack */

        struct xfrm_sec_ctx *      security;             /*   256     4 */
        struct xfrm_tmpl           xfrm_vec[6];          /*   260   360 */
}; /* size: 620, sum members: 619, holes: 1, sum holes: 1 */

Are there any fugly data dependencies here? None that I know.

In the process changed the removed the __ prefixed types, that are just for
userspace visible headers.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 3878a88ff61838e44440a9ebadd4d8c37d23b2a0..984e5c45265c44e9ed9fcca42fbe6c98bc3de383 100644 (file)
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -340,18 +340,19 @@ struct xfrm_policy
        atomic_t                refcnt;
        struct timer_list       timer;
 
-       u8                      type;
        u32                     priority;
        u32                     index;
        struct xfrm_selector    selector;
        struct xfrm_lifetime_cfg lft;
        struct xfrm_lifetime_cur curlft;
        struct dst_entry       *bundles;
-       __u16                   family;
-       __u8                    action;
-       __u8                    flags;
-       __u8                    dead;
-       __u8                    xfrm_nr;
+       u16                     family;
+       u8                      type;
+       u8                      action;
+       u8                      flags;
+       u8                      dead;
+       u8                      xfrm_nr;
+       /* XXX 1 byte hole, try to pack */
        struct xfrm_sec_ctx     *security;
        struct xfrm_tmpl        xfrm_vec[XFRM_MAX_DEPTH];
 };