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Date: Fri, 28 Sep 2007 08:15:56 -0500
From: Eric Sandeen <sandeen@sandeen.net>
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Subject: [PATCH 1/2] Use generic routines for xfs_next_bit
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To: xfs-oss <xfs@oss.sgi.com>

We can use find_next_bit, which is assembly on some arches,
to implement xfs_next_bit.  Tested on x86.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

Index: linux-2.6.22.i386/fs/xfs/xfs_bit.c
===================================================================
--- linux-2.6.22.i386.orig/fs/xfs/xfs_bit.c
+++ linux-2.6.22.i386/fs/xfs/xfs_bit.c
@@ -192,32 +192,16 @@ found:
  */
 int xfs_next_bit(uint *map, uint size, uint start_bit)
 {
-	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
-	uint result = start_bit & ~(NBWORD - 1);
-	uint tmp;
+	int result;
 
-	size <<= BIT_TO_WORD_SHIFT;
+	size <<= BIT_TO_WORD_SHIFT;
+	if (start_bit >= size)	/* beyond end of bitmap */
+		return -1;
 
-	if (start_bit >= size)
-		return -1;
-	size -= result;
-	start_bit &= (NBWORD - 1);
-	if (start_bit) {
-		tmp = *p++;
-		/* set to zero first offset bits prior to start */
-		tmp &= (~0U << start_bit);
-		if (tmp != 0U)
-			goto found;
-		result += NBWORD;
-		size -= NBWORD;
-	}
-	while (size) {
-		if ((tmp = *p++) != 0U)
-			goto found;
-		result += NBWORD;
-		size -= NBWORD;
-	}
-	return -1;
-found:
-	return result + ffs(tmp) - 1;
+	result = find_next_bit((unsigned long *)map, size, start_bit);
+
+	if (result == size)	/* no bits set */
+		return -1;
+
+	return result;
 }