On Sat, 24 Nov 2012, Theodore Ts'o wrote:
> Date: Sat, 24 Nov 2012 19:36:32 -0500
> From: Theodore Ts'o <tytso@xxxxxxx>
> To: Ext4 Developers List <linux-ext4@xxxxxxxxxxxxxxx>
> Cc: Theodore Ts'o <tytso@xxxxxxx>
> Subject: [PATCH 4/6] libext2fs: optimize rb_get_bmap_range()
>
> This simplifies the rb_get_bmap_range() function and speeds it up for
> the case where most of the bitmap is zero.
Looks good
Reviewed-by: Lukas Czerner <lczerner@xxxxxxxxxx>
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> lib/ext2fs/blkmap64_rb.c | 25 ++++++++-----------------
> 1 file changed, 8 insertions(+), 17 deletions(-)
>
> diff --git a/lib/ext2fs/blkmap64_rb.c b/lib/ext2fs/blkmap64_rb.c
> index 816f44f..0705cf2 100644
> --- a/lib/ext2fs/blkmap64_rb.c
> +++ b/lib/ext2fs/blkmap64_rb.c
> @@ -741,32 +741,23 @@ static errcode_t rb_get_bmap_range(ext2fs_generic_bitmap bitmap,
> break;
> }
>
> - pos = start;
> + memset(out, 0, (num + 7) >> 3);
> +
> for (; parent != NULL; parent = next) {
> next = ext2fs_rb_next(parent);
> ext = ext2fs_rb_entry(parent, struct bmap_rb_extent, node);
>
> - while (((pos - start) < num) &&
> - (pos < ext->start)) {
> - ext2fs_fast_clear_bit64((pos - start), out);
> - pos++;
> - }
> -
> - if ((pos - start) >= num)
> - return 0;
> + pos = ext->start;
> + if (pos < start)
> + pos = start;
>
> - while (((pos - start) < num) &&
> - (pos < (ext->start + ext->count))) {
> + while (pos < (ext->start + ext->count)) {
> + if ((pos - start) >= num)
> + return 0;
> ext2fs_fast_set_bit64((pos - start), out);
> pos++;
> }
> }
> -
> - while ((pos - start) < num) {
> - ext2fs_fast_clear_bit64((pos - start), out);
> - pos++;
> - }
> -
> return 0;
> }
>
>
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