Commit 6017b485 authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
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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

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: default avatarAkinobu Mita <>
Cc: "Theodore Ts'o" <>
Cc: Andreas Dilger <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 10d47084
......@@ -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,
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