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-rw-r--r--lib/find_last_bit.c36
1 files changed, 14 insertions, 22 deletions
diff --git a/lib/find_last_bit.c b/lib/find_last_bit.c
index 91ca09fbf6f9..3e3be40c6a6e 100644
--- a/lib/find_last_bit.c
+++ b/lib/find_last_bit.c
@@ -4,6 +4,9 @@
* 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.
+ *
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
@@ -11,37 +14,26 @@
*/
#include <linux/bitops.h>
+#include <linux/bitmap.h>
#include <linux/export.h>
-#include <asm/types.h>
-#include <asm/byteorder.h>
+#include <linux/kernel.h>
#ifndef find_last_bit
unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
{
- unsigned long words;
- unsigned long tmp;
-
- /* Start at final word. */
- words = size / BITS_PER_LONG;
+ if (size) {
+ unsigned long val = BITMAP_LAST_WORD_MASK(size);
+ unsigned long idx = (size-1) / BITS_PER_LONG;
- /* Partial final word? */
- if (size & (BITS_PER_LONG-1)) {
- tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
- - (size & (BITS_PER_LONG-1)))));
- if (tmp)
- goto found;
- }
+ do {
+ val &= addr[idx];
+ if (val)
+ return idx * BITS_PER_LONG + __fls(val);
- while (words) {
- tmp = addr[--words];
- if (tmp) {
-found:
- return words * BITS_PER_LONG + __fls(tmp);
- }
+ val = ~0ul;
+ } while (idx--);
}
-
- /* Not found */
return size;
}
EXPORT_SYMBOL(find_last_bit);