ext3: use memweight()
Akinobu Mita [Mon, 30 Jul 2012 21:41:06 +0000 (14:41 -0700)]
Convert ext3_count_free() to use memweight() instead of table lookup
based counting clear bits implementation.  This change only affects the
code segments enabled by EXT3FS_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 changes.

- Remove unnecessary map == NULL check in ext3_count_free() which
  always takes non-null pointer as the memory area.

- Fix printk format warning that only reveals with EXT3FS_DEBUG.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Jan Kara <jack@suse.cz>
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>

fs/ext3/balloc.c
fs/ext3/bitmap.c

index 25cd608..90d901f 100644 (file)
@@ -1813,7 +1813,7 @@ ext3_fsblk_t ext3_count_free_blocks(struct super_block *sb)
        brelse(bitmap_bh);
        printk("ext3_count_free_blocks: stored = "E3FSBLK
                ", computed = "E3FSBLK", "E3FSBLK"\n",
-              le32_to_cpu(es->s_free_blocks_count),
+              (ext3_fsblk_t)le32_to_cpu(es->s_free_blocks_count),
                desc_count, bitmap_count);
        return bitmap_count;
 #else
index 909d13e..ef9c643 100644 (file)
 
 #ifdef EXT3FS_DEBUG
 
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
 unsigned long ext3_count_free (struct buffer_head * map, unsigned int numchars)
 {
-       unsigned int i;
-       unsigned long sum = 0;
-
-       if (!map)
-               return (0);
-       for (i = 0; i < numchars; i++)
-               sum += nibblemap[map->b_data[i] & 0xf] +
-                       nibblemap[(map->b_data[i] >> 4) & 0xf];
-       return (sum);
+       return numchars * BITS_PER_BYTE - memweight(map->b_data, numchars);
 }
 
 #endif  /*  EXT3FS_DEBUG  */