Re: [Qemu-devel] [PATCH 2/6] dirty-bitmap: add bdrv_dirty_bitmap_next_dirty_area

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

03.08.2018 20:46, Vladimir Sementsov-Ogievskiy wrote:
> The function alters bdrv_dirty_iter_next_area(), which is wrong and
> less efficient (see next commit for description).
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>   include/block/dirty-bitmap.h |  3 +++
>   include/qemu/hbitmap.h       | 15 +++++++++++++++
>   block/dirty-bitmap.c         |  7 +++++++
>   util/hbitmap.c               | 39 +++++++++++++++++++++++++++++++++++++++
>   4 files changed, 64 insertions(+)
>
> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
> index 5dc146abf3..c02be67564 100644
> --- a/include/block/dirty-bitmap.h
> +++ b/include/block/dirty-bitmap.h
> @@ -100,6 +100,9 @@ BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BlockDriverState *bs,
>   char *bdrv_dirty_bitmap_sha256(const BdrvDirtyBitmap *bitmap, Error **errp);
>   int64_t bdrv_dirty_bitmap_next_zero(BdrvDirtyBitmap *bitmap, uint64_t start,
>                                       uint64_t bytes);
> +bool bdrv_dirty_bitmap_next_dirty_area(BdrvDirtyBitmap *bitmap,
> +                                       uint64_t *offset, uint64_t end,
> +                                       uint64_t *length);
>   BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap_locked(BlockDriverState *bs,
>                                                     BdrvDirtyBitmap *bitmap,
>                                                     Error **errp);
> diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h
> index 259bfc2936..347a46ef48 100644
> --- a/include/qemu/hbitmap.h
> +++ b/include/qemu/hbitmap.h
> @@ -303,6 +303,21 @@ unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi);
>    */
>   int64_t hbitmap_next_zero(const HBitmap *hb, uint64_t start, uint64_t bytes);
>   
> +/* hbitmap_next_dirty_area:
> + * @hb: The HBitmap to operate on
> + * @offset: in-out parameter.
> + *          in: the offset to start from
> + *          out: (if area found) start of found area
> + * @end: end of requested region. (*@offset + *@length) will be <= @end
> + * @length: length of found area
> + *
> + * If dirty area found within [@offset, @end), returns true and sets @offset
> + * and @length appropriately. Otherwise returns true and leaves @offset and
> + * @length unchanged.
> + */
> +bool hbitmap_next_dirty_area(const HBitmap *hb, uint64_t *offset,
> +                             uint64_t end, uint64_t *length);
> +
>   /* hbitmap_create_meta:
>    * Create a "meta" hbitmap to track dirtiness of the bits in this HBitmap.
>    * The caller owns the created bitmap and must call hbitmap_free_meta(hb) to
> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index a9ee814da7..c24aa0e229 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
> @@ -791,6 +791,13 @@ int64_t bdrv_dirty_bitmap_next_zero(BdrvDirtyBitmap *bitmap, uint64_t offset,
>       return hbitmap_next_zero(bitmap->bitmap, offset, bytes);
>   }
>   
> +bool bdrv_dirty_bitmap_next_dirty_area(BdrvDirtyBitmap *bitmap,
> +                                       uint64_t *offset, uint64_t end,
> +                                       uint64_t *length)
> +{
> +    return hbitmap_next_dirty_area(bitmap->bitmap, offset, end, length);
> +}
> +
>   void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
>                                Error **errp)
>   {
> diff --git a/util/hbitmap.c b/util/hbitmap.c
> index 73137c10a0..7bfcb878c1 100644
> --- a/util/hbitmap.c
> +++ b/util/hbitmap.c
> @@ -53,6 +53,9 @@
>    */
>   
>   struct HBitmap {
> +    /* Size of the bitmap, as requested in hbitmap_alloc. */
> +    uint64_t orig_size;
> +
>       /* Number of total bits in the bottom level.  */
>       uint64_t size;
>   
> @@ -238,6 +241,40 @@ int64_t hbitmap_next_zero(const HBitmap *hb, uint64_t start, uint64_t bytes)
>       return res;
>   }
>   
> +bool hbitmap_next_dirty_area(const HBitmap *hb, uint64_t *offset,
> +                             uint64_t end, uint64_t *length)
> +{
> +    HBitmapIter hbi;
> +    int64_t off1, off0;
> +    uint32_t granularity = 1UL << hb->granularity;
> +
> +    if (end == 0) {
> +        end = hb->orig_size;
> +    }
> +
> +    hbitmap_iter_init(&hbi, hb, *offset << hb->granularity);
> +    off1 = hbitmap_iter_next(&hbi, true);
> +
> +    if (off1 < 0 || off1 >= end) {
> +        return false;
> +    }
> +
> +    if (off1 + granularity >= end) {

here:
if (off1 > *offset) {

> +        *offset = off1;

}

> +        *length = end - off1;
instead:

*length = end - *offset;



> +        return true;
> +    }
> +
> +    off0 = hbitmap_next_zero(hb, off1 + granularity, end);
> +    if (off0 < 0) {
> +        off0 = end;
> +    }
> +

and here too:
if (off1 > *offset) {
> +    *offset = off1;
}
> +    *length = off0 - off1;
instead:

*length = off0 - *offset;


> +    return true;
> +}
> +
>   bool hbitmap_empty(const HBitmap *hb)
>   {
>       return hb->count == 0;
> @@ -659,6 +696,8 @@ HBitmap *hbitmap_alloc(uint64_t size, int granularity)
>       HBitmap *hb = g_new0(struct HBitmap, 1);
>       unsigned i;
>   
> +    hb->orig_size = size;
> +
>       assert(granularity >= 0 && granularity < 64);
>       size = (size + (1ULL << granularity) - 1) >> granularity;
>       assert(size <= ((uint64_t)1 << HBITMAP_LOG_MAX_SIZE));


-- 
Best regards,
Vladimir