percpu-refcount: use unsigned long for pcpu_count pointer

percpu_ref->pcpu_count is a percpu pointer with a status flag in its
lowest bit.  As such, it always goes through arithmetic operations
which is very cumbersome to do on a pointer.  It has to be first
casted to unsigned long and then back.

Let's just make the field unsigned long so that we can skip the first
casts.  While at it, rename it to pcpu_counter_ptr to clarify that
it's a pointer value.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Christoph Lameter <cl@linux-foundation.org>

diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index b62a4ee6d6ad1981abc3d08ce95d7f8915e0fab0..6f8cd4c0546cb63ca18447962cd6cbf787adb8f6 100644 (file)
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -61,7 +61,7 @@ struct percpu_ref {
         * hack because we need to keep the pointer around for
         * percpu_ref_kill_rcu())
         */
-       unsigned __percpu       *pcpu_count;
+       unsigned long           pcpu_count_ptr;
        percpu_ref_func_t       *release;
        percpu_ref_func_t       *confirm_kill;
        struct rcu_head         rcu;
@@ -99,7 +99,7 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
 static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
                                    unsigned __percpu **pcpu_countp)
 {
-       unsigned long pcpu_ptr = (unsigned long)ACCESS_ONCE(ref->pcpu_count);
+       unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr);
 
        if (unlikely(pcpu_ptr & PCPU_REF_DEAD))
                return false;

diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 087f1a04f9bc21b15acaf10894522498af09c730..94e5b624de640612a639a12c5fdfe092f77b1270 100644 (file)
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -33,7 +33,7 @@
 
 static unsigned __percpu *pcpu_count_ptr(struct percpu_ref *ref)
 {
-       return (unsigned __percpu *)((unsigned long)ref->pcpu_count & ~PCPU_REF_DEAD);
+       return (unsigned __percpu *)(ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
 }
 
 /**
@@ -51,8 +51,8 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release)
 {
        atomic_set(&ref->count, 1 + PCPU_COUNT_BIAS);
 
-       ref->pcpu_count = alloc_percpu(unsigned);
-       if (!ref->pcpu_count)
+       ref->pcpu_count_ptr = (unsigned long)alloc_percpu(unsigned);
+       if (!ref->pcpu_count_ptr)
                return -ENOMEM;
 
        ref->release = release;
@@ -153,11 +153,10 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
 void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
                                 percpu_ref_func_t *confirm_kill)
 {
-       WARN_ONCE((unsigned long)ref->pcpu_count & PCPU_REF_DEAD,
+       WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,
                  "percpu_ref_kill() called more than once!\n");
 
-       ref->pcpu_count = (unsigned __percpu *)
-               (((unsigned long) ref->pcpu_count)|PCPU_REF_DEAD);
+       ref->pcpu_count_ptr |= PCPU_REF_DEAD;
        ref->confirm_kill = confirm_kill;
 
        call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);