rcu: simplify the usage of percpu data

&percpu_data is compatible with allocated percpu data.

And we use it and remove the "->rda[NR_CPUS]" array, saving significant
storage on systems with large numbers of CPUs.  This does add an additional
level of indirection and thus an additional cache line referenced, but
because ->rda is not used on the read side, this is OK.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 14c040b18ed0..5ce197e87792 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -283,7 +283,7 @@ struct rcu_state {
         struct rcu_node *level[NUM_RCU_LVLS];   /* Hierarchy levels. */
         u32 levelcnt[MAX_RCU_LVLS + 1];         /* # nodes in each level. */
         u8 levelspread[NUM_RCU_LVLS];           /* kids/node in each level. */
-        struct rcu_data *rda[NR_CPUS];          /* array of rdp pointers. */
+        struct rcu_data __percpu *rda;          /* pointer of percu rcu_data. */
 
         /* The following fields are guarded by the root rcu_node's lock. */