From: Akinobu Mita Date: Mon, 30 Jul 2012 21:41:08 +0000 (-0700) Subject: ext4: use memweight() X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=6017b485caeae5915956190b4f3d8307021e785d;p=deliverable%2Flinux.git 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 Cc: "Theodore Ts'o" Cc: Andreas Dilger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 #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,