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authorAkinobu Mita <akinobu.mita@gmail.com>2012-07-31 01:41:08 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-31 04:25:16 +0400
commit6017b485caeae5915956190b4f3d8307021e785d (patch)
treed2f3acfc4b8ea70db019367c3561ee272343a643 /fs/ext4/bitmap.c
parent10d470849a7c6dd360e8ad4770160ad7af9adb4b (diff)
downloadlinux-6017b485caeae5915956190b4f3d8307021e785d.tar.xz
ext4: use memweight()
Convert ext4_count_free() to use memweight() instead of table lookup based counting clear bits implementation. This change only affects the code segments enabled by EXT4FS_DEBUG. Note that this memweight() call can't be replaced with a single bitmap_weight() call, although the pointer to the memory area is aligned to long-word boundary. Because the size of the memory area may not be a multiple of BITS_PER_LONG, then it returns wrong value on big-endian architecture. This also includes the following change. - Remove unnecessary map == NULL check in ext4_count_free() which always takes non-null pointer as the memory area. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/ext4/bitmap.c')
-rw-r--r--fs/ext4/bitmap.c9
1 files changed, 1 insertions, 8 deletions
diff --git a/fs/ext4/bitmap.c b/fs/ext4/bitmap.c
index a94b9c63ee5c..f8716eab9995 100644
--- a/fs/ext4/bitmap.c
+++ b/fs/ext4/bitmap.c
@@ -11,16 +11,9 @@
#include <linux/jbd2.h>
#include "ext4.h"
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
unsigned int ext4_count_free(char *bitmap, unsigned int numchars)
{
- unsigned int i, sum = 0;
-
- for (i = 0; i < numchars; i++)
- sum += nibblemap[bitmap[i] & 0xf] +
- nibblemap[(bitmap[i] >> 4) & 0xf];
- return sum;
+ return numchars * BITS_PER_BYTE - memweight(bitmap, numchars);
}
int ext4_inode_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,