2 files changed, 27 insertions, 2 deletions

diff --git a/lib/Makefile b/lib/Makefile
index 58f74d2dd396..05f8fa56a1bc 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -25,7 +25,7 @@ obj-y	+= lockref.o
 obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
          bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
          gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
-         bsearch.o find_last_bit.o find_next_bit.o llist.o memweight.o kfifo.o \
+         bsearch.o find_next_bit.o llist.o memweight.o kfifo.o \
          percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o
 obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c
index cbea5ef843aa..18072ea9c20e 100644
--- a/lib/find_next_bit.c
+++ b/lib/find_next_bit.c
@@ -1,8 +1,12 @@
-/* find_next_bit.c: fallback find next bit implementation
+/* bit search implementation
  *
  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
+ * Copyright (C) 2008 IBM Corporation
+ * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
+ * (Inspired by David Howell's find_next_bit implementation)
+ *
  * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
  * size and improve performance, 2015.
  *
@@ -13,6 +17,7 @@
  */
 
 #include <linux/bitops.h>
+#include <linux/bitmap.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 
@@ -106,6 +111,26 @@ unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
 EXPORT_SYMBOL(find_first_zero_bit);
 #endif
 
+#ifndef find_last_bit
+unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
+{
+        if (size) {
+                unsigned long val = BITMAP_LAST_WORD_MASK(size);
+                unsigned long idx = (size-1) / BITS_PER_LONG;
+
+                do {
+                        val &= addr[idx];
+                        if (val)
+                                return idx * BITS_PER_LONG + __fls(val);
+
+                        val = ~0ul;
+                } while (idx--);
+        }
+        return size;
+}
+EXPORT_SYMBOL(find_last_bit);
+#endif
+
 #ifdef __BIG_ENDIAN
 
 /* include/linux/byteorder does not support "unsigned long" type */