[RFC 2/4] pid_namespace: remove .kref field for !CONFIG_PID_NS

From: Rasmus Villemoes
Date: Wed Sep 30 2015 - 16:50:33 EST


When there's only one global pid_namespace (init_pid_ns), the kref
field is unused (since both get_pid_ns and put_pid_ns are
no-ops). While we only save a few bytes by removing it, it could also
help catch users manipulating ->kref directly.

Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
include/linux/pid_namespace.h | 2 ++
kernel/pid.c | 2 ++
2 files changed, 4 insertions(+)

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 03a84a0cdc75..1cac17eb0775 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -22,7 +22,9 @@ struct pidmap {
struct fs_pin;

struct pid_namespace {
+#ifdef CONFIG_PID_NS
struct kref kref;
+#endif
struct pidmap pidmap[PIDMAP_ENTRIES];
struct rcu_head rcu;
int last_pid;
diff --git a/kernel/pid.c b/kernel/pid.c
index 909d3dcd8085..25332679a4d3 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -68,9 +68,11 @@ static inline int mk_pid(struct pid_namespace *pid_ns,
* the scheme scales to up to 4 million PIDs, runtime.
*/
struct pid_namespace init_pid_ns = {
+#ifdef CONFIG_PID_NS
.kref = {
.refcount = ATOMIC_INIT(2),
},
+#endif
.pidmap = {
[ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL }
},
--
2.1.3

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