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-rw-r--r--lib/find_next_bit.c27
1 files changed, 26 insertions, 1 deletions
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 */