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    SubjectRe: [PATCH v3 7/9] ext2: use memweight()
    On Sat 09-06-12 09:50:36, Akinobu Mita wrote:
    > Convert ext2_count_free() to use memweight() instead of table lookup
    > based counting clear bits implementation. This change only affects
    > the code segments enabled by EXT2FS_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 ext2_count_free() which
    > always takes non-null pointer as the memory area.
    >
    > - Fix printk format warning that only reveals with EXT2FS_DEBUG.
    >
    > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
    > Cc: Jan Kara <jack@suse.cz>
    Acked-by: Jan Kara <jack@suse.cz>

    Honza

    > Cc: linux-ext4@vger.kernel.org
    > ---
    > v3: rewrite to keep ext2_count_free() as a wrapper for memweight()
    >
    > fs/ext2/balloc.c | 14 ++------------
    > fs/ext2/ialloc.c | 1 +
    > 2 files changed, 3 insertions(+), 12 deletions(-)
    >
    > diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
    > index 1c36139..376aa77 100644
    > --- a/fs/ext2/balloc.c
    > +++ b/fs/ext2/balloc.c
    > @@ -1444,19 +1444,9 @@ ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp)
    >
    > #ifdef EXT2FS_DEBUG
    >
    > -static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
    > -
    > -unsigned long ext2_count_free (struct buffer_head * map, unsigned int numchars)
    > +unsigned long ext2_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 /* EXT2FS_DEBUG */
    > diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
    > index c13eb7b..8f370e01 100644
    > --- a/fs/ext2/ialloc.c
    > +++ b/fs/ext2/ialloc.c
    > @@ -644,6 +644,7 @@ unsigned long ext2_count_free_inodes (struct super_block * sb)
    > }
    > brelse(bitmap_bh);
    > printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
    > + (unsigned long)
    > percpu_counter_read(&EXT2_SB(sb)->s_freeinodes_counter),
    > desc_count, bitmap_count);
    > return desc_count;
    > --
    > 1.7.7.6
    >
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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