futex: Use runtime constants for __futex_hash() hot path

diff --git a/kernel/futex/core.c b/kernel/futex/core.c
@@ -48,23 +48,19 @@
 #include <vdso/futex.h>
 
+#include <asm/runtime-const.h>
+
 #include "futex.h"
 #include "../locking/rtmutex_common.h"
 
-/*
- * The base of the bucket array and its size are always used together
- * (after initialization only in futex_hash()), so ensure that they
- * reside in the same cacheline.
- */
-static struct {
-	unsigned long            hashmask;
-	unsigned int		 hashshift;
-	struct futex_hash_bucket *queues[MAX_NUMNODES];
-} __futex_data __read_mostly __aligned(2*sizeof(long));
+static u32 __futex_mask __ro_after_init;
+static u32 __futex_shift __ro_after_init;
+static struct futex_hash_bucket **__futex_queues __ro_after_init;
 
-#define futex_hashmask	(__futex_data.hashmask)
-#define futex_hashshift	(__futex_data.hashshift)
-#define futex_queues	(__futex_data.queues)
+static __always_inline struct futex_hash_bucket **futex_queues(void)
+{
+	return runtime_const_ptr(__futex_queues);
+}

@@ -395,13 +391,13 @@ __futex_hash(union futex_key *key, struct futex_private_hash *fph, struct futex_
 	 * NOTE: this isn't perfectly uniform, but it is fast and
 	 * handles sparse node masks.
 	 */
-		node = (hash >> futex_hashshift) % nr_node_ids;
+		node = runtime_const_shift_right_32(hash, __futex_shift) % nr_node_ids;
 		if (!node_possible(node)) {
 			node = find_next_bit_wrap(node_possible_map.bits, nr_node_ids, node);
 		}
 	}
 
-	return &futex_queues[node][hash & futex_hashmask];
+	return &futex_queues()[node][runtime_const_mask_32(hash, __futex_mask)];

@@ -2019,10 +2015,21 @@ static int __init futex_init(void)
 	hashsize = max(4, hashsize);
 	hashsize = roundup_pow_of_two(hashsize);
 #endif
-	futex_hashshift = ilog2(hashsize);
+	__futex_mask = hashsize - 1;
+	__futex_shift = ilog2(hashsize);
 	size = sizeof(struct futex_hash_bucket) * hashsize;
 	order = get_order(size);
 
+	__futex_queues = kcalloc(nr_node_ids, sizeof(*__futex_queues), GFP_KERNEL);
+
+	runtime_const_init(shift, __futex_shift);
+	runtime_const_init(mask,  __futex_mask);
+	runtime_const_init(ptr,   __futex_queues);
+
+	barrier();
+
+	BUG_ON(!futex_queues());
+
 	for_each_node(n) {
 		struct futex_hash_bucket *table;
@@ -2036,10 +2043,9 @@ static int __init futex_init(void)
 		for (i = 0; i < hashsize; i++)
 			futex_hash_bucket_init(&table[i]);
 
-		futex_queues[n] = table;
+		futex_queues()[n] = table;
 	}
 
-	futex_hashmask = hashsize - 1;
 	pr_info("futex hash table entries: %lu (%lu bytes on %d NUMA nodes, total %lu KiB, %s).\n",