On Sat 09-06-12 09:50:37, Akinobu Mita wrote:
> 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@xxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
Acked-by: Jan Kara <jack@xxxxxxx>
Honza
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
> Cc: linux-ext4@xxxxxxxxxxxxxxx
> ---
> v3: rewrite to keep ext3_count_free() as a wrapper for memweight()
>
> fs/ext3/balloc.c | 2 +-
> fs/ext3/bitmap.c | 12 +-----------
> 2 files changed, 2 insertions(+), 12 deletions(-)
>
> diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
> index 25cd608..90d901f 100644
> --- a/fs/ext3/balloc.c
> +++ b/fs/ext3/balloc.c
> @@ -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
> diff --git a/fs/ext3/bitmap.c b/fs/ext3/bitmap.c
> index 909d13e..ef9c643 100644
> --- a/fs/ext3/bitmap.c
> +++ b/fs/ext3/bitmap.c
> @@ -11,19 +11,9 @@
>
> #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 */
> --
> 1.7.7.6
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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