Re: [Qemu-devel] [PATCH v2 08/13] block: Support meta dirty bitmap

[John Snow <jsnow@redhat.com>]

On 01/20/2016 01:11 AM, Fam Zheng wrote:
> The added group of operations enables tracking of the changed bits in
> the dirty bitmap.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>

Reviewed-by: John Snow <jsnow@redhat.com>

> ---
>  block/dirty-bitmap.c         | 51 ++++++++++++++++++++++++++++++++++++++++++++
>  include/block/dirty-bitmap.h |  9 ++++++++
>  2 files changed, 60 insertions(+)
> 
> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index bd7758b..d75dcf7 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
> @@ -37,6 +37,7 @@
>   */
>  struct BdrvDirtyBitmap {
>      HBitmap *bitmap;            /* Dirty sector bitmap implementation */
> +    HBitmap *meta;              /* Meta dirty bitmap */
>      BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */
>      char *name;                 /* Optional non-empty unique ID */
>      int64_t size;               /* Size of the bitmap (Number of sectors) */
> @@ -102,6 +103,56 @@ BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
>      return bitmap;
>  }
>  
> +/* bdrv_create_meta_dirty_bitmap
> + *
> + * Create a meta dirty bitmap that tracks the changes of bits in @bitmap. I.e.
> + * when a dirty status bit in @bitmap is changed (either from reset to set or
> + * the other way around), its respective meta dirty bitmap bit will be marked
> + * dirty as well.
> + *
> + * @bitmap: the block dirty bitmap for which to create a meta dirty bitmap.
> + * @granularity: how many bytes of bitmap data does each bit in the meta bitmap
> + * track.
> + */
> +void bdrv_create_meta_dirty_bitmap(BdrvDirtyBitmap *bitmap,
> +                                   int granularity)
> +{
> +    assert(!bitmap->meta);
> +    bitmap->meta = hbitmap_create_meta(bitmap->bitmap,
> +                                       BDRV_SECTOR_SIZE * BITS_PER_BYTE);
> +}
> +
> +void bdrv_release_meta_dirty_bitmap(BdrvDirtyBitmap *bitmap)
> +{
> +    assert(bitmap->meta);
> +    hbitmap_free_meta(bitmap->bitmap);
> +    bitmap->meta = NULL;
> +}
> +
> +int bdrv_dirty_bitmap_get_meta(BlockDriverState *bs,
> +                               BdrvDirtyBitmap *bitmap, int64_t sector,
> +                               int nb_sectors)
> +{
> +    uint64_t i;
> +    int gran = bdrv_dirty_bitmap_granularity(bitmap) >> BDRV_SECTOR_BITS;
> +
> +    /* To optimize: we can make hbitmap to internally check the range in a
> +     * coarse level, or at least do it word by word. */
> +    for (i = sector; i < sector + nb_sectors; i += gran) {
> +        if (hbitmap_get(bitmap->meta, i)) {
> +            return true;
> +        }
> +    }
> +    return false;
> +}
> +
> +void bdrv_dirty_bitmap_reset_meta(BlockDriverState *bs,
> +                                  BdrvDirtyBitmap *bitmap, int64_t sector,
> +                                  int nb_sectors)
> +{
> +    hbitmap_reset(bitmap->meta, sector, nb_sectors);
> +}
> +
>  bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap)
>  {
>      return bitmap->successor;
> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
> index 120bac6..d9b281a 100644
> --- a/include/block/dirty-bitmap.h
> +++ b/include/block/dirty-bitmap.h
> @@ -9,6 +9,9 @@ BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
>                                            uint32_t granularity,
>                                            const char *name,
>                                            Error **errp);
> +void bdrv_create_meta_dirty_bitmap(BdrvDirtyBitmap *bitmap,
> +                                   int granularity);
> +void bdrv_release_meta_dirty_bitmap(BdrvDirtyBitmap *bitmap);
>  int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
>                                         BdrvDirtyBitmap *bitmap,
>                                         Error **errp);
> @@ -35,6 +38,12 @@ void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
>                             int64_t cur_sector, int nr_sectors);
>  void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
>                               int64_t cur_sector, int nr_sectors);
> +int bdrv_dirty_bitmap_get_meta(BlockDriverState *bs,
> +                               BdrvDirtyBitmap *bitmap, int64_t sector,
> +                               int nb_sectors);
> +void bdrv_dirty_bitmap_reset_meta(BlockDriverState *bs,
> +                                  BdrvDirtyBitmap *bitmap, int64_t sector,
> +                                  int nb_sectors);
>  BdrvDirtyBitmapIter *bdrv_dirty_iter_new(BdrvDirtyBitmap *bitmap,
>                                           uint64_t first_sector);
>  void bdrv_dirty_iter_free(BdrvDirtyBitmapIter *iter);
> 

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—js