1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 22eaed188907..a856e0aee73b 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -20,6 +20,7 @@
 #include <linux/completion.h>
 #include <linux/kobject.h>
 #include <linux/refcount.h>
+#include <linux/log2.h>
 
 #include "dm-stats.h"
 
@@ -228,4 +229,25 @@ void dm_free_md_mempools(struct dm_md_mempools *pools);
  */
 unsigned int dm_get_reserved_bio_based_ios(void);
 
+#define DM_HASH_LOCKS_MAX 64
+
+static inline unsigned int dm_num_hash_locks(void)
+{
+	unsigned int num_locks = roundup_pow_of_two(num_online_cpus()) << 1;
+
+	return min_t(unsigned int, num_locks, DM_HASH_LOCKS_MAX);
+}
+
+#define DM_HASH_LOCKS_MULT  4294967291ULL
+#define DM_HASH_LOCKS_SHIFT 6
+
+static inline unsigned int dm_hash_locks_index(sector_t block,
+					       unsigned int num_locks)
+{
+	sector_t h1 = (block * DM_HASH_LOCKS_MULT) >> DM_HASH_LOCKS_SHIFT;
+	sector_t h2 = h1 >> DM_HASH_LOCKS_SHIFT;
+
+	return (h1 ^ h2) & (num_locks - 1);
+}
+
 #endif