Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

[mv-sheeva.git] / kernel / taskstats.c

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 5f82ccd103928f27dcd704660cc004485d9bcf76..69691eb4b715da804555e04c79aa4ba44ec2bdd3 100644 (file)
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -348,25 +348,47 @@ static int parse(struct nlattr *na, struct cpumask *mask)
        return ret;
 }
 
+#ifdef CONFIG_IA64
+#define TASKSTATS_NEEDS_PADDING 1
+#endif
+
 static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
 {
        struct nlattr *na, *ret;
        int aggr;
 
-       /* If we don't pad, we end up with alignment on a 4 byte boundary.
-        * This causes lots of runtime warnings on systems requiring 8 byte
-        * alignment */
-       u32 pids[2] = { pid, 0 };
-       int pid_size = ALIGN(sizeof(pid), sizeof(long));
-
        aggr = (type == TASKSTATS_TYPE_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;
-       if (nla_put(skb, type, pid_size, pids) < 0)
+
+       if (nla_put(skb, type, sizeof(pid), &pid) < 0)
                goto err;
        ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
        if (!ret)
@@ -455,6 +477,18 @@ out:
        return rc;
 }
 
+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
+       return size;
+}
+
 static int cmd_attr_pid(struct genl_info *info)
 {
        struct taskstats *stats;
@@ -463,8 +497,7 @@ static int cmd_attr_pid(struct genl_info *info)
        u32 pid;
        int rc;
 
-       size = nla_total_size(sizeof(u32)) +
-               nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+       size = taskstats_packet_size();
 
        rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
        if (rc < 0)
@@ -493,8 +526,7 @@ static int cmd_attr_tgid(struct genl_info *info)
        u32 tgid;
        int rc;
 
-       size = nla_total_size(sizeof(u32)) +
-               nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+       size = taskstats_packet_size();
 
        rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
        if (rc < 0)
@@ -569,8 +601,7 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
        /*
         * Size includes space for nested attributes
         */
-       size = nla_total_size(sizeof(u32)) +
-               nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+       size = taskstats_packet_size();
 
        is_thread_group = !!taskstats_tgid_alloc(tsk);
        if (is_thread_group) {