taskstats: use the libnl API to align nlattr on 64-bit

Goal of this patch is to use the new libnl API to align netlink attribute
when needed.
The layout of the netlink message will be a bit different after the patch,
because the padattr (TASKSTATS_TYPE_STATS) will be inside the nested
attribute instead of before it.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 21f82c2..b3f05ee 100644 (file)
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -357,10 +357,6 @@ static int parse(struct nlattr *na, struct cpumask *mask)
        return ret;
 }
 
-#if defined(CONFIG_64BIT) && !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
-#define TASKSTATS_NEEDS_PADDING 1
-#endif
-
 static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
 {
        struct nlattr *na, *ret;
@@ -370,29 +366,6 @@ static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
                        ? TASKSTATS_TYPE_AGGR_PID
                        : TASKSTATS_TYPE_AGGR_TGID;
 
-       /*
-        * The taskstats structure is internally aligned on 8 byte
-        * boundaries but the layout of the aggregrate reply, with
-        * two NLA headers and the pid (each 4 bytes), actually
-        * force the entire structure to be unaligned. This causes
-        * the kernel to issue unaligned access warnings on some
-        * architectures like ia64. Unfortunately, some software out there
-        * doesn't properly unroll the NLA packet and assumes that the start
-        * of the taskstats structure will always be 20 bytes from the start
-        * of the netlink payload. Aligning the start of the taskstats
-        * structure breaks this software, which we don't want. So, for now
-        * the alignment only happens on architectures that require it
-        * and those users will have to update to fixed versions of those
-        * packages. Space is reserved in the packet only when needed.
-        * This ifdef should be removed in several years e.g. 2012 once
-        * we can be confident that fixed versions are installed on most
-        * systems. We add the padding before the aggregate since the
-        * aggregate is already a defined type.
-        */
-#ifdef TASKSTATS_NEEDS_PADDING
-       if (nla_put(skb, TASKSTATS_TYPE_NULL, 0, NULL) < 0)
-               goto err;
-#endif
        na = nla_nest_start(skb, aggr);
        if (!na)
                goto err;
@@ -401,7 +374,8 @@ static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
                nla_nest_cancel(skb, na);
                goto err;
        }
-       ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
+       ret = nla_reserve_64bit(skb, TASKSTATS_TYPE_STATS,
+                               sizeof(struct taskstats), TASKSTATS_TYPE_NULL);
        if (!ret) {
                nla_nest_cancel(skb, na);
                goto err;
@@ -500,10 +474,9 @@ static size_t taskstats_packet_size(void)
        size_t size;
 
        size = nla_total_size(sizeof(u32)) +
-               nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
-#ifdef TASKSTATS_NEEDS_PADDING
-       size += nla_total_size(0); /* Padding for alignment */
-#endif
+               nla_total_size_64bit(sizeof(struct taskstats)) +
+               nla_total_size(0);
+
        return size;
 }