From f1fd306a91f875e65af0e04855b23adda6831ac9 Mon Sep 17 00:00:00 2001
From: Al Viro
Date: Fri, 26 Aug 2011 22:38:50 -0400
Subject: minixfs: kill manual hweight(), simplify

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/minix/bitmap.c | 41 ++++++++++++++---------------------------
 1 file changed, 14 insertions(+), 27 deletions(-)

(limited to 'fs/minix/bitmap.c')

diff --git a/fs/minix/bitmap.c b/fs/minix/bitmap.c
index 7c82c29429d7..ef175cb8cfd8 100644
--- a/fs/minix/bitmap.c
+++ b/fs/minix/bitmap.c
@@ -16,39 +16,26 @@
 #include <linux/bitops.h>
 #include <linux/sched.h>
 
-static const int nibblemap[] = { 4,3,3,2,3,2,2,1,3,2,2,1,2,1,1,0 };
-
 static DEFINE_SPINLOCK(bitmap_lock);
 
-static unsigned long count_free(struct buffer_head *map[], unsigned blocksize, __u32 numbits)
+/*
+ * bitmap consists of blocks filled with 16bit words
+ * bit set == busy, bit clear == free
+ * endianness is a mess, but for counting zero bits it really doesn't matter...
+ */
+static __u32 count_free(struct buffer_head *map[], unsigned blocksize, __u32 numbits)
 {
-	unsigned i, j, sum = 0;
-	struct buffer_head *bh;
-	unsigned numblocks = minix_blocks_needed(numbits, blocksize);
-  
-	for (i=0; i<numblocks-1; i++) {
-		if (!(bh=map[i])) 
-			return(0);
-		for (j=0; j<bh->b_size; j++)
-			sum += nibblemap[bh->b_data[j] & 0xf]
-				+ nibblemap[(bh->b_data[j]>>4) & 0xf];
-	}
+	__u32 sum = 0;
+	unsigned blocks = DIV_ROUND_UP(numbits, blocksize * 8);
 
-	if (numblocks==0 || !(bh=map[numblocks-1]))
-		return(0);
-	i = ((numbits - (numblocks-1) * bh->b_size * 8) / 16) * 2;
-	for (j=0; j<i; j++) {
-		sum += nibblemap[bh->b_data[j] & 0xf]
-			+ nibblemap[(bh->b_data[j]>>4) & 0xf];
+	while (blocks--) {
+		unsigned words = blocksize / 2;
+		__u16 *p = (__u16 *)(*map++)->b_data;
+		while (words--)
+			sum += 16 - hweight16(*p++);
 	}
 
-	i = numbits%16;
-	if (i!=0) {
-		i = *(__u16 *)(&bh->b_data[j]) | ~((1<<i) - 1);
-		sum += nibblemap[i & 0xf] + nibblemap[(i>>4) & 0xf];
-		sum += nibblemap[(i>>8) & 0xf] + nibblemap[(i>>12) & 0xf];
-	}
-	return(sum);
+	return sum;
 }
 
 void minix_free_block(struct inode *inode, unsigned long block)
-- 
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